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Punjab State Board PSEB 10th Class Science Book Solutions Chapter 2 Acids, Bases and Salts Textbook Exercise Questions and Answers.

PSEB Solutions for Class 10 Science Chapter 2 Acids, Bases and Salts

PSEB 10th Class Science Guide Acids, Bases and Salts Textbook Questions and Answers

Question 1.
A solution turns red litmus blue, its pH is likely to be :
(a) 1
(b) 4
(c) 5
(d) 10.
Answer:
(d) 10.

Question 2.
A solution reacts with crushed egg-shells to give a gas that turns lime- water milky. The solution contains:
(a) NaCl
(b) HCl
(c) LiCl
(d) KC1.
Answer:
(b) HCl

Question 3.
10 mL of a solution of NaOH is found to be completely neutralised by 8 mL of a given solution of HCl. If we take 20 mL of the same solution of NaOH, the amount of HCl solution (the same solution as before) required to neutralise it will be :
(a) 4 mL
(b) 8 mL
(c) 12 mL
(d) 16 mL.
Answer:
(d) 16 mL.

Question 4.
Which one of the following types of medicines is used for treating indigestion?
(a) Antibiotic
(b) Analgesic
(c) Antacid
(d) Antiseptic.
Answer:
(c) Antacid

Question 5.
Write word equations and then balance equations for the reaction taking place when :
(a) dilute sulphuric acid reacts with zinc granules
Answer:
Zinc granules + Dilute sulphuric acid → Zinc sulphate + Hydrogen

(b) dilute hydrochloric acid reacts with magnesium ribbon
Answer:
Magnesium ribbon + Hydrochloric acid → Magnesium chloride + Hydrogen

(c) dilute sulphuric acid reacts with aluminium powder
Answer:
Aluminium powder + Dilute sulphuric acid → Aluminium sulphate + Hydrogen

(d) dilute sulphuric acid reacts with iron filings.
Answer:
Iron filings + Dilute sulphuric acid → Iron (II) sulphate + Hydrogen.

Question 6.
Compounds such as alcohols and glucose also contain hydrogen but are not categorised as acids. Describe an activity to prove it.
Answer:
Fix two nails on a cork and place it in a 100 ml beaker. Connect these nails to a 6 volt battery through a bulb and switch as shown in the figure.

Aqueous solution of alcohol or glucose does not conduct electricity

Pour some aqueous solution of alcohol or aqueous solution of glucose in the beaker so that nails dip in it. Switch on the current. The bulb does not glow indicating that alcohol and glucose don’t dissociate in aqueous solution and hence
do not produce H⁺ ions although they (aq)
contain hydrogen.

Question 7.
Why does not distilled water conduct electricity, whereas rainwater does?
Answer:

• Distilled water does not conduct electricity because it contains no ions.
• Rainwater contains ions due to dissolved salts, hence it conducts electric current.

Question 8.
Why do acids not show acidic behaviour in the absence of water?
Answer:
This is because in the absence of water, acids do not dissociate to give hydrogen ions > H⁺_(aq)

Question 9.
Five solutions A, B, C, D and E when tested with universal indicator showed pH as 4, 1, 11, 7 and 9 respectively. Which solution is :
(a) neutral?
(b) strongly alkaline?
(c) strongly acidic?
(d) weakly acidic?
(e) weakly alkaline?
Arrange the pH in increasing order of hydrogen-ion concentration.

Solution	pH	Nature of Solution
A	4	Weakly acidic
B	1	Strongly acidic
C	11	Strongly alkaline
D	7	Neutral
E	9	Weakly alkaline

The increasing order of hydrogen-ion concentration is :
11 < 9 < 7 < 4 < 1 (pH values).

Question 10.
Equal lengths of magnesium ribbons are taken in test tubes A and B. Hydrochloric acid (HCl) is added to test tube A, while acetic acid (CH₃COOH) is added to test tube B. Amount and concentration taken for both the acids are same. In which test tube will the fizzing occur more vigorously and why?
Answer:
Fizzing occurs more vigorous in test tube A as compared to in test tube B. This is because concentration of hydrogen ion, It is more in test tube A than in test tube B, as hydrochloric acid a strong acid and acetic acid (CH₃COOH) is a weak acid.

Question 11.
Fresh milk has a pH of 6. How do you think the pH will change as it turns into curd? Explain your answer.
Answer:
Its pH will decrease due to the production of lactic acid which is acidic in nature.

Question 12.
A milkman adds a very small amount of baking soda to fresh milk.
(a) Why does he shift the pH of the fresh milk from 6 to slightly alkaline?
Answer:
So that the milk is not spoiled readily and medium remains basic.

(b) Why does this milk take a long time to set as curd?
Answer:
Because the lactic acid produced during curding reacts with baking soda.

Question 13.
Plaster of Paris should be stored in a moisture-proof container. Explain why?
Answer:
This is because in presence of moisture, plaster of Paris sets to give a hard mass.

Question 14.
What is a neutralisation reaction? Give two examples.
Answer:
The interaction of an acid with a base to form salt and water is called neutralisation reaction.

Examples :

Question 15.
Give two important uses of washing soda and baking soda.
Answer:
(a) Uses of washing soda :

1. It is used in the manufacture of glass and soap.
2. It is used in the manufacture of borax.

(b) Uses of baking soda :

1. It is used in soda-acid fire extinguisher.
2. It is used for making baking powder.

Science Guide for Class 10 PSEB Acids, Bases and Salts InText Questions and Answers

Question 1.
You have been provided with three test tubes. One of them contains distilled water and the other two contain an acidic solution and a basic solution, respectively. If you are given only red litmus paper, how will you identify the contents of each test tube?
Answer:
Dip red litmus paper in solution repeatedly in each tube.
(a) The tube in which the red litmus paper turns purple contains distilled water.
(b) The tube in which red litmus paper turns blue contains basic solution.
(c) The tube in which red litmus paper remains red contains acidic solution.

Question 2.
Why should curd and sour substances not be kept in brass and copper vessels?
Answer:
Curd and other sour substances contain acids which react with the metal surface of brass and copper vessels to produce toxic compounds which are unfit for consumption.

Question 3.
Which gas is usually liberated when an acid reacts with a metal? Illustrate with an example. How will you test for the presence of this gas?
Answer:
When an acid reacts with metal, generally hydrogen is produced.
e.g. Mg + 2 HCl(Dil) → MgCl₂ + H₂ ↑

Pass this gas (H₂) through soap solution. The soap bubbles filled with the gas will rise up. If a burning splinter is brought near the gas, the bubble will burn with a ‘pop’ sound.

Question 4.
Metal compound A reacts with dilute hydrochloric acid to produce effervescence. The gas evolved extinguishes a burning candle. Write a balanced chemical equation for the reaction if one of the compounds formed is calcium chloride.
Answer:

CO₂ extinguishes a burning candle.

Question 5.
Why do HCl, HNO₃ etc. show acidic characters in aqueous solutions while solutions of compounds like alcohol and glucose do not show acidic character?
Answer:
HCl, HNO₃ etc undergo dissociation in water to give Hydrogen ions, H⁺_(aq) ions and show acidic characteristics. There are compounds like alcohol and glucose don’t dissociate in water to give hydrogen ions, H⁺_(aq) ions. Hence, they don’t show acidic properties.

Question 6.
Why does an aqueous solution of acid conduct electricity?
Answer:
The aqueous solution of an acid contains ions such as hydrogen ions, H⁺_(aq) and other anions. Hence it conducts electricity.

Question 7.
Why does dry HCl gas not change the colour on the dry litmus paper?
Answer:
This is because dry HCl gas is a covalent compound and it does not undergo dissociation to give hydrogen ions, H⁺_(aq) and hence no change in colour of dry litmus paper.

Question 8.
While diluting an acid, why is it recommended that the acid should be added to water and not water to the acid?
Answer:
The process of dissolving an acid or a base in water is an exothermic process. This is because if water is added to concentrated acid, the heat generated may cause the mixture to splash out and cause burns. The glass container may also break due to excessive local heating.

Question 9.
How is the concentration of hydronium ions (H₃O⁺) affected when a solution of an acid is diluted?
Answer:
The concentration of hydronium ions decreases when a solution of an acid is diluted.

Question 10.
How is the concentration of hydroxide ions [OH^–] affected when excess base is dissolved in a solution of sodium hydroxide?
Answer:
When excess of base is dissolved in a solution of sodium hydroxide, the concentration of OH ions increases.

Question 11.
You have two solutions, A and B. The pH of solution A is 6 and pH of solution B is 8. Which solution has more hydrogen ion concentration? Which of this is acidic and which one is basic?
Answer:
In solution A, [H⁺_(aq)] = 10^-6 M, pH < 7
In solution B, [H⁺_(aq)] = 10^-8 M. pH > 7

∴ Then the solution A has more hydrogen ion concentration.
Solution A is acidic.
Solution B is basic.

Question 12.
What effect does the concentration of H⁺_(aq) ions have on the nature of the solution?
Answer:

• If [H⁺] < 10^-7 M, it is basic solution.
• If [H⁺] >10^-7 M, it is an acidic solution.
• If [H⁺] = 10^-7 M, it is a neutral aqueous solution.

Question 13.
Do basic solutions also have H⁺_(aq) ions? If yes, then why are these basic?
Answer:
Basic solutions also contain H⁺_(aq) ions. But in basic solutions :
[H⁺_(aq)] < 10^-7 M
and [OH^–] > 10^-7 M
Since [OH^–_(aq)] is more than [H⁺_(aq)], hence these are basic solutions.

Question 14.
Under what soil condition do you think a farmer would treat the soil of his Helds with quick lime (calcium oxide) or slaked lime (calcium hydroxide) or chalk (calcium carbonate)?
Answer:
If the pH of the soil is less than 7, i.e. it is acidic, the farmer will treat the soil with quick lime, slaked lime, chalk.

Question 15.
What is the common name of the compound CaOCl₂?
Answer:
Bleaching powder.

Question 16.
Name the substance which on treatment with chlorine yields bleaching powder.
Answer:
Dry slaked lime.

Question 17.
Name the sodium compound which is used for softening hard water.
Answer:
Washing soda.

Question 18.
What will happen if a solution of sodium hydrocarbonate is heated? Give the equation of the reaction involved.
Answer:
It decomposes to give sodium carbonate, water and carbon dioxide gas (which is colourless, odourless and turns lime water milky).

Question 19.
Write an equation to show the reaction between Plaster of Paris and water.
Answer:

Punjab State Board PSEB 10th Class Science Book Solutions Chapter 4 Carbon and its Compounds Textbook Exercise Questions and Answers.

PSEB Solutions for Class 10 Science Chapter 4 Carbon and its Compounds

PSEB 10th Class Science Guide Carbon and its Compounds Textbook Questions and Answers

Question 1.
Ethane, with the molecular formula C₂H₆ has :
(a) 6 covalent bonds
(b) 7 covalent bonds
(c) 8 covalent bonds
(d) 9 covalent bonds.
Answer:
(b) 7 covalent bonds

Question 2.
Butanone is a four-carbon compound with the functional group :
(a) carboxylic acid
(b) aldehyde
(c) ketone
(d) alcohol.
Answer:
(c) ketone

Question 3.
While cooking, if the bottom of the vessel is getting blackened on the outside, it means that :
(а) the food is not cooked completely
(b) the fuel is not burning completely
(c) the fuel is wet
(d) the fuel is burning completely.
Answer:
(b) the fuel is not burning completely

Question 4.
Explain the nature of the covalent bond using the bond formation in CH₃Cl.
Answer:
The formation of CH₃Cl can be represented as :

Carbon forms single covalent bonds with three H- atoms and one Cl – atom by sharing one electron pair with each C-H bonds are non-polar. But C – Cl bond is polar because C and H leave almost same electronegativity whereas Cl has more electronegativity than carbon.

Question 5.
Draw the electron dot structures for :
(a) ethanoic acid
Answer:

(b) H₂S
Answer:

(c) propanone
Answer:

(d) F₂.
Answer:

Question 6.
What is an homologous series? Explain with an example.
Answer:
A series of compounds having similar structural formulae, same functional group and hence similar chemical properties is called a homologous series. In the homologous series any two adjacent members differ by CH2 unit in their molecular formulae.

For example homologous series of aldehydes (or alkanals) can be represented as :

H – CHO	Methanal
CH3 – CHO	Ethanal
CH3 – CH2 – CHO	Propanal
CH3 – CH2 – CH2 – CHO	Butanal
CH3 – CH2 – CH2 – CH2 – CHO	Pentanal and so on.

Question 7.
How can ethanol and ethanoic acid be differentiated on the basis of their physical and chemical properties?
Answer:
Differences between ethanol and ethanoic acid

Ethanol	Ethanoic acid
1. It is a colourless liquid having a pleasant smell.	1. It is colourless liquid having vineger like smell.
2. It has no action with a litmus solution.	2. It turns blue litmus solution red.
3. It has no action with sodium hydrogen carbonate solution.	3. It decomposes sodium hydrogen carbonate solution giving brisk effervescence of carbon dioxide gas.

Question 8.
Why does micelle formation take place when soap is added to water? Will a micelle be formed in other solvents such as ethanol also?
Answer:
Soap molecule has two ends, one is hydrophilic, and it dissolves in water, while the other end is hydrophobic, and it dissolves in hydrocarbons. When soap is at the surface of water , the hydrophobic ‘tail’ of soap will not be soluble in water and the soap will align along the surface of water with the ionic end in water and the hydrocarbon ‘tail’ pointing out of water.

Inside water, these molecules have a unique orientation which keeps the hydrocarbon portion out of the water. This is achieved due to the formation clusters of molecules in which the hydrophobic tails are in the interior of the cluster and the ionic ends are on the surface of the cluster. This formation is called a micelle.

Such micelles can be formed in other polar solvents like ethanol.

Question 9.
Why are carbon and its compounds used as fuels for most applications?
Answer:
Carbon and its compounds are used as fuels for most applications because they bum producing a large amount of heat and light.

Question 10.
Explain the formation of scum when hard water is treated with soap.
Answer:
When soap is added to hard water, the soluble calcium and magnesium salts present in it react with soap to give insoluble calcium salt of soap which produces scum.

Question 11.
What change will you observe if you test soap with litmus paper (red and blue)?
Answer:
Soap solution will turn red litmus paper blue because soap is alkaline in nature.

Question 12.
What is hydrogenation? What is its industrial application?
Answer:
The addition of hydrogen to unsaturated hydrocarbons in the presence of catalysts like palladium, platinum, nickel etc. to give saturated hydrocarbons is called hydrogenation.

This reaction is used for hydrogenation of liquid vegetable oils using a nickel catalyst to get artificial or vanaspati ghee.

Question 13.
Which of the following hydrocarbons undergo addition reaction : C₂H₆, C₃H₈, C₃H₆, C₂H₂ and CH₄.
Answer:
Out of C₂H₆, C₃H₈, C₃H₆, C₂H₂ and CH₄; C₃H₆ and C₂H₂ undergo addition reactions because they contain multiple bonds.

Question 14.
Give a test that can be used to differentiate chemically between butter and cooking oil.
Answer:
Distinction between Butter and Cooking oil:

Butter	Cooking Oil
1. It is solid at room temperature.	1. It is liquid at room temperature.
2. Mix equal volumes of HgCl2 solution in 50% alcohol and 5% iodine solution in alcohol. To this add lg of butter. Violet colour does not fade away.	2. Mix equal volumes of HgCl2 solution in 50% alcohol and 5% solution of iodine in alcohol. To this add 1 ml of cooking oil. Violet colour fades away.
3. Take 2 g of butter in a test tube. To this add 1ml of cone. HCl and a few drops of 2% furfural solution in alcohol. Shake and allow to stand for 5 – 10 minutes. No rose red coloration appears.	3. Take 2 g of cooking oil in a test tube. To this add 1 ml of cone. HCl and a few drops of 2% .furfural solution in alcohol. Shake it and allow to stand for 5 – 10 minutes. Rose red coloration is obtained.

Question 15.
Explain the mechanism of the cleansing action of soaps.
Answer:
Mechanism of cleansing action of Soap:
Soaps are sodium or potassium salts of higher fatty acids e.g. sodium palmitate, C₁₅H₃₁COO^–Na⁺, sodium stearate, C₁₇H₃₅COO^–Na⁺ etc. A molecule of soap consists of two parts :

1. a long chain hydrocarbon part (C₁₅H₃₁^–, C₁₇H₃₅ …. etc.) which is soluble in oil and
2. ionic part on polar group, – COO^–Na⁺ which is soluble in water. Thus a molecule of soap can be represented as :

The long hydrocarbon chain is insoluble in water but soluble in oil and greases whereas the ionic or polar part is soluble in water. Soap has a capacity to clean a dirty piece of cloth whereas ordinary water cannot. The dirty clothes contain greasy and oily substance (dirt). Soap molecules dissociate in water to give carboxylate ion (RCOO^–) and cation (Na⁺). When soap added to dirty clothes dipped in water, the hydrocarbon part of carboxylate group dissolving in greasy or oily dirt particles where the polar (COO^–) group remain attached to water. In this way each oil droplet acquires negative charge.

The cleansing action of Soap

These negative charged oil droplets called micelles cannot coalesce and hence form a stable emulsion water. These small droplets along with dirt can be easily washed away with water. Thus the soap helps in removing greasy dirt by producing a stable oil in wrater type emulsion. Also the soap reduces surface tension of water. Hence cloth is wetted more effectively and is cleaned.

Science Guide for Class 10 PSEB Carbon and its Compounds InText Questions and Answers

Question 1.
What would be the electron-dot structure of carbon dioxide which has the formula CO₂?
Answer:
In carbon dioxide, carbon atoms are bonded with two oxygen atoms. The atomic number of carbon is 6, and it has four electrons in the outer shell.

To make an octet it requires four electrons. Oxygen requires only two electrons in the outer shell. Therefore electron-dot structure will be :

Every oxygen atom is joined to carbon atom by double bond.

Question 2.
What would be the electron-dot structure of a molecule of sulphur which is made up of eight atoms of sulphur? (HINT. The eight atoms of sulphur are joined together in the form of ring.)
Answer:
The atomic number of sulphur is 16

Sulphur has 6 electrons in the outermost shell and to complete an octet it requires 2 electrons.
∴ Sulphur atom will share 2 electrons. It’s chemical formula is S₈.

Question 3.
How many structural isomers can you draw for pentane?
Answer:
Three ; n-Pentane, iso-pentane, neo-pentane.
Structural isomers can be drawn for pentane.

Question 4.
What are the two properties of carbon which lead to the huge number of carbon compounds we see around us?
Answer:

1. Catenation: The carbon atoms have an astonishing property to combine and form bond with other carbon atoms to form long chain compounds. This property is known as catenation. In this, either long chain of carbon are in ring form or the carbon atoms join in single, double or triple bond.
2. Tetravalency: Carbon has four electrons in the outermost shell. That is why its valency is four and it has got capacity to make bonds with other elements. Oxygen, Hydrogen, Nitrogen, Sulphur, Chlorine and many other elements can make new compounds with the help of carbon.

Question 5.
What will be the formula and electron dot structure of cyclopentane?
Answer:
Molecular formula of cyclopentane = C₅ H_{2 × 5} = C₅H₁₀

Question 6.
Draw the structures for following compounds :
Are structural isomers possible for bromopentane?
(i) Ethanoic acid
Answer:
Ethanoic acid (CH₃COOH)

(ii) Bromopentane
Answer:

Due to exchange of position of carbon with bromine, many isomers of bromopentane are possible.
For example :

(iii) Butanone
Answer:

(iv) Hexanal.
Answer:

Question 7.
How would you name the following compounds?
(i) CH₃ – CH₂ – Br
Answer:
Bromoethane

Answer:
Methanal

Answer:
Hex-1-yne.

Question 8.
Why is the conversion of ethanol to ethanoic acid an oxidation reaction?
Answer:
This is because in this reaction oxygen gets added to ethanol.

Question 9.
A mixture of oxygen and ethyne is burnt for welding. Can you tell why a mixture of ethyne and air is not used?
Answer:
A mixture of ethyne and air is not burnt for welding. This is because air also contains nitrogen along with oxygen. Nitrogen will also burn in oxygen producing oxides of nitrogen such as nitre oxide (NO) and nitrogen dioxide (NO₂) which cause pollution.

Question 10.
How would you distinguish experimentally between an alcohol and a carboxylic acid?
Answer:
The following two tests are used :

• Litmus test: Treat the given compound with blue litmus solutions. If the blue litmus solution turns red, it is a carboxylic acid and if does not turn red, it is an alcohol.
• Sodium bicarbonate test: Add some sodium bicarbonate solution to the given compound. If their is a brisk evolution of a colourless and odourless gas (CO₂) which turns freshly prepared lime water milk, it is carboxylic acid and if their is no effervescence, it is an alcohol.

Question 11.
What are oxidising agents?
Answer:

• The substances which can oxidise other substances by giving oxygen are called oxidising agents.
• Examples: Alkaline potassium permanganate solution, acidified potassium dichromate solution, etc.

Question 12.
Would you be able to check if water is hard using a detergent?
Answer:
No, we can’t check whether the water is hand or soft using a detergent.

Question 13.
People use a variety of methods to wash clothes. Usually after adding the soap, they ‘beat’ the clothes on a stone, or beat it with a paddle, scrub with a brush, or the mixture is agitated necessary to get clean clothes?
Answer:
This is because when soap molecules dissolve in the dirt, the dirt is somewhat loosened from the clothes, and in order to remove it from clothes, the clothes have to be beaten on a stone or beaten with a paddle or scrubbed with a brush or mixture has to be agitated in washing machines.

Punjab State Board PSEB 10th Class Science Book Solutions Chapter 1 Chemical Reactions and Equations Textbook Exercise Questions and Answers.

PSEB Solutions for Class 10 Science Chapter 1 Chemical Reactions and Equations

PSEB 10th Class Science Guide Chemical Reactions and Equations Textbook Questions and Answers

Question 1.
Which of the statements about the reaction below are incorrect?
2PbO(s) + C(s) → 2Pb(s) + CO₂(g)
(a) Lead is getting reduced.
(b) Carbon dioxide is getting oxidised.
(c) Carbon is getting oxidised.
(d) Lead oxide is being reduced.
(i) (a) and (b)
(ii) (a) and (c)
(iii) (a), (b) and (c)
(iv) all.
Answer
(i) (a) and (b)

Question 2.
Fe₂O₃ + 2Al → Al₂O₃ + 2Fe
The above reaction is an example of a
(a) combination reaction.
(b) double displacement reaction.
(c) decomposition reaction.
(d) displacement reaction.
Answer:
(d) displacement reaction.

Question 3.
What happens when dilute hydrochloric acid is added to iron filings?
Tick the correct answer.
(a) Hydrogen gas and iron chloride are produced.
(b) Chlorine gas and iron hydroxide are produced.
(c) No reaction takes place.
(d) Iron salt and water are produced.
Answer:
(a) Hydrogen gas and iron chloride are produced.

Question 4.
What is a balanced chemical equation? Why should chemical equations be balanced?
Answer:
Balanced chemical equation. It is a chemical equation in which number of atoms of each element are equal on both sides of the equation.

The chemical equation should be balanced because law of conservation of mass holds good i.e., the total mass of the reactants must be equal to the total mass of the products.

Question 5.
Translate the following statements into chemical equations and then balance them :
(a) Hydrogen gas combines with nitrogen to form ammonia.
Answer:
3H₂ (g) + N₂ → 2NH₃ (g)

(b) Hydrogen sulphide gas burns in air to give water and sulphur dioxide.
Answer:
2H₂S (g) + 3O₂ (g) → 2H₂O (l) + 2SO₂ (g)

(c) Barium chloride reacts with aluminium sulphate to give aluminium chloride and a precipitate of barium sulphate.
Answer:
3BaCl₂ + A12(SO₄)₃ → 2AlCl₃ (aq) + 3BaSO₄ (s)↓

(d) Potassium metal reacts with water to give potassium hydroxide and hydrogen gas.
Answer:
2K (s) + 2H₂O (l) → 2KOH (aq) + H₂ (g)

Question 6.
Balance the following chemical equations :
(a) HNO₃ + Ca(OH)₂ → Ca(NO₃)₂ + H₂O
Answer:
2HNO₃ + Ca(OH)₂ → Ca(NO₃)₂ + 2H₂O

(b) NaOH + H₂SO4 → Na₂SO₄ + H₂O
Answer:
2NaOH + H₂SO₄ → Na₂SO₄ + 2H₂O

(c) NaCl + AgNO₃ → AgCl + NaNO₃
Answer:
NaCl + AgNO₃ → AgCl + NaNO₃

(d) BaCl₂ + H₂SO₄ → BaSO₄ + HCl
Answer:
BaCl₂ + H₂SO₄ → BaSO₄ + 2HCl

Question 7.
Write the balanced chemical equations for the following reactions :
(a) Calcium hydroxide + Carbon dioxide → Calcium carbonate + Water
Answer:
Ca(OH)₂ + CO₂ → CaCO₃ + H₂O

(b) Zinc + Silver nitrate → Zinc nitrate + Silver.
Answer:
Zn + 2AgNO₃ → Zn(NO₃)₂ + 2Ag

(c) Aluminium + Copper chloride → Aluminium chloride + Copper.
Answer:
2Al + 3CuCl₂ → 2AlCl₃ + 3Cu

(d) Barium chloride + Potassium sulphate → Barium sulphate + Potassium chloride.
Answer:
BaCl₂ + K₂SO₄ → BaSO₄ + 2KCl

Question 8.
Write the balanced chemical equation for the following reaction and identify the type of reaction in each case.
(a) Potassium bromide (aq) + Barium iodide (aq) → Potassium iodide (aq) + Barium bromide (s)
Answer:
2KBr (aq) + Bal₂ (aq) → 2KI (aq) + BaBr₂ (aq) — Double displacement reaction

(b) Zinc carbonate (s) → Zinc oxide (s) + Carbon dioxide (g)
Answer:
ZnCO₃ (s) → ZnO (s) + CO₂ (g) — Decomposition reaction

(c) Hydrogen (g) + Chlorine (g) → Hydrogen chloride (g)
Answer:
H₂(g) + Cl₂ (g) → 2HCl(g) — Combination reaction

(d) Magnesium (s) + Hydrochloric acid (aq) → Magnesium chloride (aq) + Hydrogen (g)
Answer:(a)
Mg(s) + 2HCl(aq) → MgCl₂ (aq) + H₂ (g) — Displacement reaction

Question 9.
What is meant by exothermic and endothermic reactions? Give examples.
Or
Differentiate between exothermic and endothermic reactions.
Answer:
Exothermic reaction. It is a chemical reaction in which heat energy is given out.
e.g. C (s) + O₂ (g) → CO₂ + Heat energy
NaOH (aq) + HCl (aq) → NaCl (aq) + H₂O (l) + Heat energy

Endothermic reaction : It is a chemical reaction in which heat energy is absorbed,
e.g. N₂ (g) + O₂ (g) → 2NO (g) — Heat energy
C (S) + H₂O (g) → CO + H₂ (g) — Heat energy.

Question 10.
Why is respiration considered as an exothermic reaction? Explain.
Answer:
During respiration oxidation of glucose occurs which produces heat energy.

Question 11.
Why are decomposition reactions called opposite of combination reactions? Write equations for these reactions.
Answer:
During decomposition a single substance breaks down into two or more substances which is just the reverse of combination reaction.

Examples for decomposition reactions are :

Question 12.
Write one equation each for decomposition reactions where energy is supplied in the form of heat, light or electricity.
Answer:

Here electrical energy is supplied to bring about the reaction.

Question 13.
What is the difference between the displacement and double displacement reactions? Write equations for these reactions.
Answer:
Displacement reaction: In this reaction a more active element displaces less active element from solution of its compound. Examples:
Fe (s) + CuSO₄ (aq) → FeSO₄ (aq) + Cu (s) ↓
Zn (s) + CuSO₄ (aq) → ZnSO₄ (aq) + Cu (s) ↓

Double displacement reaction: The reaction in which there is an exchange of ions between two reactants is called a double displacement reaction.
AgNO₃ (aq) + NaCl (aq) AgCl (s) ↓ + NaNO₃ (aq)
BaCl₂ (aq) + Na₂SO₄ (aq) BaSO₄ (s) ↓ + 2NaCl (aq)

Question 14.
In the refining of silver, the recovery of silver from silver nitrate solution involved displacement by copper metal. Write down the reaction involved.
Answer:
Cu (s) + 2AgNO₃ (aq) → Cu(NO₃)₂ (aq) + 2Ag ↓

Question 15.
What do you mean by precipitation reaction? Explain by giving examples.
Answer:
Precipitation reaction. A reaction in which an insoluble product or precipitate is produced is called precipitation reaction.
AgNO₃ (aq) + NaCl (aq) → AgCl (s) ↓ + NaNO₃ (aq)
BaCl₂ (aq) + Na2SO₄ (aq) → BaSO₄ (s) ↓ + 2NaCl (aq)

Question 16.
Explain the following in terms of gain or loss of oxygen with two examples each :
(a) Oxidation (b) Reduction.
Answer:
(a) Oxidation: A chemical reaction in which a substance gains oxygen or loses hydrogen is called oxidation.
Examples

(b) Reduction: A chemical reaction in which a substance loses oxygen or gains hydrogen is called reduction.

Question 17.
A shiny brown coloured element ‘X’ on heating in air becomes black in colour. Name the element ‘X’ and the black coloured compound formed.
Answer:
The element X is copper.

Therefore the black coloured compound formed is copper (II) oxide (CuO).

Question 18.
Why do we apply paint on iron articles?
Answer:
The iron articles can be protected from rusting by applying paint on them so that the iron surface does not come in contact with air (or oxygen) and moisture which causes rusting.

Question 19.
Oil and fat containing food items are flushed with nitrogen. Why?
Answer:
This is because food items are prevented from oxidation by oxygen or air.

Question 20.
Explain the following terms with one example each :
(a) Corrosion
Answer:
Corrosion: The slow eating up of metals by the action of air and moisture on their surfaces is called corrosion. For example, iron undergoes corrosion or rusting in the presence of moist air.

(b) Rancidity.
Answer:
Rancidity: When fats and oils or food containing oils and fats get oxidised with air or oxygen, their smells and tastes change, This process is called rancidity. For example, the packet containing potato chips is flushed with nitrogen gas to avoid rancidity.

Science Guide for Class 10 PSEB Chemical Reactions and Equations InText Questions and Answers

Question 1.
Why should a magnesium ribbon be cleaned before burning in air?
Answer:
Magnesium ribbon should be cleaned before burning to remove the protective layer of basic magnesium carbonate from its surface.

Question 2.
Write the balanced equation for the following chemical reactions.
(i) Hydrogen + Chlorine → Hydrogen chloride
Answer:
H₂ + Cl₂ → 2HCl

(ii) Barium chloride + Aluminium Sulphate → Barium Sulphate + Aluminium Chloride
Answer:
3BaCl₂ + Al₂(SO₄)₃ → 3BaSO₄ + 2AlCl₃

(iii) Sodium + Water → Sodium hydroxide + Hydrogen
Answer:
2Na + 2H₂O → 2NaOH + H₂

Question 3.
Write a balanced chemical equation with state symbols for the following reactions.
(i) Solutions of barium chloride and sodium sulphate in water react to give insoluble sulphate and the solution of sodium chloride.
Answer:
BaCl₂(aq) + Na₂SO4(aq) → BaSO₄(s) + 2NaCl(aq)

(ii) Sodium hydroxide solution (in water) reacts with hydrochloric acid solution (in water) to produce sodium chloride and water.
Answer:
NaOH (aq) + HCl (aq) → NaCl (aq) + H₂O (l)

Question 4.
A solution of substance “X’ is used for white washing.
(i) Name the substance X’and write its formula.
Answer:
X is calcium oxide (quick lime) and its formula is CaO.

(ii) Write the reaction of the substance X named in (i) above with water.
Answer:
CaO (s) + H₂O(l) → Ca(OH)₂ (aq)

Question 5.
Why is the amount of gas collected in one of the test tubes in activity 1.7 double of the amount collected in the other? Name this gas.
Answer:
When electric current is passed through acidulated water, the reaction taking place is

Therefore hydrogen and oxygen produced are in the ratio 2 : 1 by volume. Hence volume of gas collected in one test tube is double the volume of gas collected in the other tube and this gas is hydrogen.

Question 6.
Why does the colour of copper sulphate solution change, when an iron nail is dipped in it?
Answer:
This is because iron displaces copper from copper sulphate solution.
Therefore, the concentration of copper sulphate solution decreases and blue colour of solution gradually fades away.

The concentration of copper sulphate solution decreases as ferrous sulphate is produced.

Question 7.
Give an example of a double displacement reaction other than the one given in the activity 1.10 given in textbook
Answer:
NaCl (aq) + AgNO₃(ag) → NaNO₃(aq) +AgCl(s) ↓

Question 8.
Identify the substances that are oxidised and the substances that are reduced in the following reactions :
(i) 4Na(s) + O₂(g) → 2Na₂O (s)
(ii) CuO(s) + H₂(g) → Cu(s) + H₂O(l)
Answer:

Substance oxidised	Substance reduced
1. Na(s)	H2
2. H2	CuO(s)

Punjab State Board PSEB 10th Class Science Book Solutions Chapter 6 Life Processes Textbook Exercise Questions and Answers.

PSEB Solutions for Class 10 Science Chapter 6 Life Processes

PSEB 10th Class Science Guide Life Processes Textbook Questions and Answers

Question 1.
The kidneys in human beings are a part of the system for :
(a) nutrition
(b) respiration
(c) excretion
(d) transportation.
Answer:
(c) excretion.

Question 2.
The xylem in plants are responsible for :
(a) transport of water
(b) transport of food
(c) transport of amino acids
(d) transport of oxygen.
Answer:
(a) transport of water.

Question 3.
The autotrophic mode of nutrition requires :
(a) CO₂ and water
(b) Chlorophyll
(c) Sunlight
(d) All of the above.
Answer:
(d) All of above.

Question 4.
The breakdown of pyruvate to give CO₂, water and energy takes place in :
(a) cytoplasm
(b) mitochondria
(c) chloroplast
(d) nucleus
Answer:
(b) mitochondria.

Question 5.
How are fats digested in our bodies? Where does the process take place?
Answer:
Digestion of fats takes place in the intestine. The fats are emulsified by the bile salts present in bile. The emulsified fats are acted upon by pancreatic lipase (strepsin) which hydrolyses fats into fatty acids and glycerol. The intestinal lipase also hydrolyses the emulsified fats into fatty acids and glycerol.

Question 6.
What is the role of saliva in the digestion of food?
Answer:
Role of saliva

• Saliva lubricates the food and facilitates mastication.
• Saliva binds the food molecules together.
• Saliva contains ptyalin (salivary amylase) enzyme which acts on starch, glycogen and other carbohydrates to form maltose.

Question 7.
What are the necessary conditions for autotrophic nutrition and what are its byproducts?
Answer:
Photosynthesis is essential in case of autotrophic nutrition

Conditions required for photosynthesis

• CO₂ is necessary for photosynthesis.
• Water is required.
• Sunlight is necessary for photosynthesis.
• Chlorophyll is essential for photosynthesis.
• By-products. Molecular oxygen is liberated as a byproduct.

Question 8.
What are the differences between aerobic respiration and anaerobic respiration? Name some organisms that use anaerobic mode of respiration.
Answer:
(a) Differences between aerobic and anaerobic respiration

Aerobic respiration	Anaerobic respiration
1. It takes place in the presence of oxygen.	1. It takes place in the absence of oxygen.
2. It is completed in cytoplasm and mitochondria of cells.	2. It is completed in the cytoplasm only.
3. It involves the complete oxidation of glucose into CO2 and H2O and a large amount of energy is released.	3. It involves the incomplete oxidation of glucose into CO2 and alcohol or lactic acid and less amount of energy is released.
4. The process is harmless.	4. It is toxic to plants.

(b) Anaerobic respiration takes place in bacteria and yeast.

Question 9.
How are alveoli designed to maximise the exchange of gases?
Answer:

Question 10.
What would be the consequences of a deficiency of haemoglobin in our bodies?
Answer:
Haemoglobin is a respiratory pigment present in RBC of blood. It has high affinity for oxygen. One molecule of haemoglobin carries 4 molecules of oxygen. If simple diffusion were to move oxygen in our body, it is estimated that it would take 3 years for a molecule of oxygen to reach tip of toes from lungs.

Question 11.
Describe double circulation in human beings. Why is it necessary?
Answer:
Double circulation. In human beings heart is four-chambered, having right and left auricles and right and left ventricles. The right auricle receives the deoxygenated blood from the body and sends it into the right ventricle that pumps it to the lungs via a pulmonary arch for oxygenation. The left auricle receives oxygenated blood from the lungs and sends it into the left ventricle, which pumps it to the body through a single aortic arch.

Significance:

• Thus, the deoxygenated and oxygenated blood remain fully separate, and there is complete double circulation.
• It increases efficiency.

Double circulation of blood in birds and mammals.

Question 12.
What are the differences between the transport of materials in xylem and phloem?
Answer:
Differences between transport in xylem and phloem

Transport in xylem	Transport in phloem
1. Water and minerals are transported through xylem.	1. Sucrose, amino acids and other substances are transported through phloem.
2. Xylem helps in upward movement, i.e. from roots to stem, branches and leaves.	2. Phloem is responsible for downward and lateral movement from leaves to other parts.

Question 13.
Compare the functioning of alveoli in the lungs and nephrons in the kidneys with respect to their structure and functioning.
Answer:

• Alveoli of lungs remove CO₂ as a waste during exchange of gases and nephrons filter wastes from blood.
• Alveoli are supplied with extensive network of blood capillaries for gaseous exchange. Bowman’s capsule surrounds a cluster of capillaries for filtration.
• Both increases surface area either for gaseous exchange or filtration.
• Urea and uric acid wastes are removed in the nephron.
• Both purify blood lungs alveoli by removing waste gases and nephrons by filtering the waste products in the form of urine.

Science Guide for Class 10 PSEB Life Processes InText Questions and Answers

Question 1.
Why is diffusion insufficient to meet the energy requirements of multicellular organisms like humans?
Answer:
In multicellular organisms, all the cells of body may not be in direct contact with the surrounding source of oxygen i.e. environment, thus simple diffusion will not meet the oxygen requirements of all the cells. These organisms require specialised organs to meet the oxygen requirement.

Question 2.
What criteria do we use to decide whether something is alive?
Answer:
Features of living organisms

• Movements
• Growth
• Metabolism
• Cellular body
• Nutrition
• Respiration
• Transportation
• Excretion
• Respond to stimuli
• Reproduction.

Question 3.
What are outside raw materials used by living organism?
Answer:
Outside raw materials used by living organism

• Energy obtained from food.
• Oxygen: Required for breaking down of carbon based molecules to liberate energy in the body.
• Water: It is required for proper digestion of food and other functions in the body. It is raw material for photosynthesis in plants. All reactions occur in solution form in the body.
• CO₂ Raw material for photosynthesis in plants. All reactions occur in solution form in the body.

Question 4.
What processes would you consider essential for maintaining life?
Answer:

• Nutrition
• Respiration
• Transportation
• Excretion.

Question 5.
What are the differences between autotrophic and heterotrophic nutrition?
Answer:
Differences between Autotrophic and Heterotrophic nutrition

Autotrophic Nutrition	Heterotrophic Nutrition
1. It occurs in green plants and blue green algae.	1. It occurs in animals and insectivorous plants.
2. CO2 and water are raw materials which combine to form organic compound.	2. They depend on plants and herbivore for their food.
3. They need chlorophyll and sunlight	3. There is no need of chlorophyll and sunlight,

Question 6.
Where do the plants get each of raw materials required for photosynthesis? (PB. Board 2011)
Answer:
Raw materials of photosynthesis

• CO₂
• Water.
• Nitrogen

1. CO₂ is obtained from air. It enters the leaf through stomatal openings.
2. Water is obtained from soil. It enters the leaf through the mid-rib and vein from the root which absorbs it from the soil.
3. Nitrogen: It is obtained from soil.

Question 7.
What is the role of acid in our stomach?
Answer:
HCl is obtained from gastric glands present in the wall of the stomach.

Functions of HCl:

• It provides acidic medium. It is required for the action of enzymes. It changes the pH of food from almost neutral to acidic medium (from pH 7 to 2)
• Activates the inactive proenzyme propepsin into active pepsin.
• Kills the bacteria present in food.
• It softens calcium.
• It regulates the opening and closing of the pyloric aperture.

Question 8.
What is the function of digestive enzymes?
Answer:
Role of digestive enzymes: These enzymes convert the complex non-diffusible form of food into simple diffusible form.

• Ptyalin converts starch into maltose.
• Pepsin breaks down proteins into peptides and amino acids.
• Rennin curdles milk protiens so that they can stay for longer period to be acted upon by pepsin.
• Lipase acts on fats and forms fatty acid and glycerol.
• Maltase acts on maltose and forms glucose.

Question 9.
How is small intestine designed to absorb digested food?
Answer:
Small intestine is a long tubular structure. The inner wall of small intestine is thrown into folds called villi. The absorptive cells have numerous finger-like processes called microvilli. They increase the surface area for absorption of food. These villi have blood vessels named lacteals from absorption of food.

Question 10.
What advantage over an aquatic organism does a terrestrial organism have with regard to obtaining oxygen for respiration?
Answer:
The amount of oxygen dissolved in water is very low as compared to the amount of oxygen in air. Thus these organisms have to make less efforts to obtain oxygen.

Question 11.
What are the different ways in which glucose is oxidised to provide energy in various organisms?
Answer:
Different pathways to provide energy from glucose

Question 12.
How is oxygen and CO₂ transported in human beings?
Answer:
1. Transport of oxygen: It is transported from respiratory organs to body cells,
1. Haemoglobin helps in the transport of oxygen. In the alveoli of the lungs, the haemoglobin (Hb) present in red blood corpuscles combines with oxygen to form oxyhaemoglobin. When the blood reaches the tissue, oxygen is released from the oxyhaemoglobin for the consumption by the tissues.
Hb + O₂ → HbO₂

2. Some of O₂ is transported in the solution form by plasma of blood.

2. Transport of CO₂

• CO₂ diffuses into blood plasma to form physical solution.
• CO₂ forms unstable carbonic acid with water and is transported as such.
• CO₂ is also transported from tissue to lungs as bicarbonates.

Question 13.
How are lungs designed in human beings to maximise the area for exchange of gases?
Answer:
Within the lungs, the primary bronchi divides into smaller and smaller tubes which finally terminate into balloon-like structures called alveoli. These alveoli increase the surface area for exchange of gases. There are 750 million alveoli in the lungs of man. If the alveolar surface is spread out it would cover about 80 m2. Thus it makes efficient exchange of gases.

Each alveolus or air sac has a diameter of 75 to 300 microns and has a very thin wall. The walls of the alveoli are elastic and are supplied with capillaries. Through these thin walls gases are exchanged between the capillaries and the air sacs.

Question 14.
What are the components of the transport system in human beings? What are the functions of these components?
Answer:
There are two main transport systems in human beings :

1. Blood vascular system.
2. Lymphatic system.

Components of blood vascular system

• Blood: It is a reddish viscous fluid connective tissue. In an adult human being, it is 5-6 litres in amount. Blood consists of two parts – plasma and formed elements. (RBCs, WBCs and blood platelets). Blood transports digested food, oxygen, carbon dioxide, nitrogenous wastes and hormones in the body.
• Heart: It is a hollow, muscular pumping organ. The heart sends the blood to lungs. Heart pumps the blood in the body.
• Blood vessels: The blood vessels which carry oxygenated blood are called arteries. They divide to form capillaries of finer dimensions. Exchange of materials takes place across the capillaries. It is possible because the walls of capillaries are extremely thin. The blood from the tissues is returned by veins.

Components of Lymphatic system

1. Lymph: It acts as middle man between blood and tissue. It destroys harmful bacteria
2. Lymph vessels
3. Lymph capillaries
4. Lymph nodes

Question 15.
Why is it necessary to separate oxygenated and deoxygenated blood in mammals and birds?
Answer:

• In the heart of these organisms the left side has oxygenated blood and right side deoxygenated blood.
• The separation of blood allows a highly efficient supply of oxygen to the body.
• It is essential for such animals which have high energy needs.
• They also constantly use energy for maintaining body heat.

Question 16.
What are the components of transport system in highly organised plants?
Answer:
Components of transport system in plants

• Xylem tissue. Vessels and tracheids of roots, stems and leaves are concerned with transport of water and minerals in plants.
• Phloem consists of sieve tubes and companion cells. It transports food, amino acid, phytohormones and other substances from leaves to various parts of plants.

Question 17.
How are water and minerals transported in plants?
Answer:
Transport of water and minerals
1. In xylem tissue, vessels and tracheids of the roots, stems and leaves are interconnected to form a continuous system of water conducting channels reaching all parts of the plants.

2. Plants absorb water and minerals through their entire surface i.e., roots, stem and leaves. However, mainly the water is absorbed by roots from soil.

3. The area of young roots where most of the absorption takes place is the root hair zone.

4. This zone is the area of greatest permeability.

5. Passage of water in root or pathway of water in root

• The entry of water into the root hair dilutes the cell sap. Thus water molecules in root hair increase as compared to adjacent cortical cells.
• Water reaches the passage cells of endodermis. These passage cells lie opposite the xylem.
• They allow water to entre the pericycle.
• So, water enters the xylem from pericycle for upward movement of sap.

6. The Ascent of Sap:
The upward movement of water from the root towards the top of the plant in the xylem vessels is called ascent of sap. The upward transport of water and minerals in plants which are in some cases as tall as 400 ft. poses a serious problem.

7. Transpiration also helps in the absorption and upward movement of water and minerals dissolved in it from roots to the leaves.

Question 18.
How is food transported in plants?
Answer:
Transport of food in plants:
The food prepared in the green leaves of plants is transported through phloem in the form of sucrose solution to storage organs of roots, seeds and fruits. This process is called translocation. This process requires energy. It is provided by ATP molecules. This increases the osmotic pressure in the tissue causing water to move into it. This pressure moves the material in the phloem to tissues which have less pressure.

Question 19.
Describe the structure and functioning of nephron.
Or
How does urine formation occur in human?
Answer:
Structure of a Nephron:
A nephron is made up of:

• a globular double-walled Bowman’s capsule around a clump of capillaries or glomerulus, and
• a tubule surrounded by blood capillaries.

The tubule consists of
(a) a proximal convoluted portion
(b) the loop of Henle, with descending and ascending limbs, and
(c) a distal convoluted part.

The nephron empties into a collecting duct. The two million nephrons of a human being, end to end would extend for nearly 80 km. All the collecting ducts discharge into a central cavity of the kidney (pelvis) that connects to the ureter.

Functioning of Nephron
Urine is formed by 3 processes: glomerular filtration, tubular reabsorption and tubular secretion in the nephrons of the kidney.
1. Ultrafiltration (Glomerular filtration):
Blood is filtered under pressure in the glomeruli present in the cup-like structure of Bowman’s capsule. Glomerular (nephric) filtrate is formed.

Nephron and its function

2. Tubular reabsorption:
In the PCT, entire glucose, amino acids, vitamins and hormones, most of the inorganic ions are reabsorbed by active transport, most of water by osmosis, and some urea by back diffusion from nephric filtrate.
Loop of Henle mainly concentrates urine to conserve water. Here, some inorganic ions are actively taken up and some water leaves by osmosis.

3. Tubular secretion:
In the DCT, collecting tubule and collecting duct, many ions, water (depending upon availability) are secreted in to DCT and collecting duct.
Urine formed passes into bladder from kidney through ureters.

Question 20.
What are the methods used by plants to get rid of excretory products?
Answer:
Excretory products of plants include CO₂, salts, resins, tanins latex etc. Excretion in Plants

• Excess of water passes out during transpiration.
• Plants get rid of dead tissue as a measure to eliminate waste.
• Waste products may be stored in cellular vacuoles.
• Waste products may be stored in leaves which fall off.
• Resins and gums are stored in old xylem.
• Plants also excrete wastes into soil.
• Aquatic plants lose their waste products by diffusion into the water.

Question 21.
How is the amount of urine produced regulated?
Answer:

• Amount of urine formed depends upon the availability of water in the body.
• ADH (Antidiuretic Hormone) regulate the amount of water.
• Osmoregulation helps in regulation of salts and water.
• Urine is stored in urinary bladder.

Punjab State Board PSEB 10th Class Science Book Solutions Chapter 9 Heredity and Evolution Textbook Exercise Questions and Answers.

PSEB Solutions for Class 10 Science Chapter 9 Heredity and Evolution

PSEB 10th Class Science Guide Heredity and Evolution Textbook Questions and Answers

Question 1.
A Mendelian experiment consisted of breeding tall pea plants bearing violet flowers with short pea plants bearing white flowers. The progeny all bore violet flowers, but almost half of them were short. This suggests that the genetic make-up of the tall parent can be depicted as :
(a) TTWW
(b) TTww
(c) TtWW
(d) TtWw.
Answer:
(c) TtWW.

Question 2.
An example of homologous organs is :
(а) our arm and a dog’s fore-leg
(б) our teeth and an elephant’s tusks
(c) potato and runners of grass
(d) All of the above.
Answer:
(d) All of the above.

Question 3.
In evolutionary terms, we have more in common with :
(а) a Chinese school-boy
(b) a chimpanzee
(c) a spider
(d) a bacterium.
Answer:
(a) a Chinese school-boy.

Question 4.
A study found that children with light-coloured eyes are likely to have parents with light-coloured eyes. On this basis, can we say anything about whether the light eye colour trait is dominant or recessive? Why or why not?
Answer:
On this basis we cannot say that light eye colour is dominant or recessive until a cross is made between parent having light eye colour and another with dark eye colour. Only then it will be possible to predict the dominant or recessive nature of the gene.

Question 5.
How are the areas of study of evolution and classification interlinked?
Answer:
Evolution and classification are interlinked as evident from following points :

• Characteristics are shared by most of the organisms. The characteristic in the next level of classification will be shared by most and not by all.
• Cell designs also indicate this relationship.
• Groups formed during classification are related to their similarities.

Question 6.
Explain the terms homologous and analogous organs with example.
Answer:
Homologous organs: The organs of different classes have different forms because they have to perform different functions but their structures basically remain similar. Such organs are called homologous organs.

Example:

• Fore limbs of amphibians, birds and mammals have same fundamental structural plans but perform different functions.
• In plants, the homologous organs may be a thorn of Bougainvillea or a tendril of cucurbita both arising in axillary position.

Analogous organs: The organs are quite different in their structure and origin but similar in function. Such organs are known as analogous organs. The presence of analogous organs proves that different structures can be modified to perform a similar function. Analogy indicates convergent evolution.
Examples. The wings of insects and vertebrates perform the same function.

Question 7.
Outline a project which aims to find the dominant coat colour in dogs.
Answer:
Make a chart or thermocol sheet showing the following monohybrid cross

Dominance of black coat colour in dogs

Question 8.
Explain the importance of fossils in deciding evolutionary relationship.
Answer:

Question 9.
What evidence do we have for the origin of life from inanimate matter?
Answer:
Urey and Miller provided experimental evidence regarding origin of life from inanimate matter. They assembled an atmosphere similar to that, thought to exist on early earth.

In a spark flask they collected ammonia, methane and hydrogen sulphide, but no free oxygen over water at a temperature just below 100°C and sparks were passed through the mixture of gases to stimulate lightning. At the end they obtained organic molecules such as amino acid, urea, sugars. Amino acids which make up protein molecules. Thus they showed life originated from inanimate matter.

Question 10.
Explain how sexual reproduction gives rise to more viable Variation than asexual reproduction. How does this affect the evolution of those organisms that reproduce sexually?
Answer:
Genetic variations arise in nature as a result of following mechanism during sexual reproduction are more viable and raw materials of evolution.

• Crossing over during gamete formation.
• Random segregation of chromosome during meiosis at the time of gamete formation has decreased.
• Random rejoining of gametes having different genetic set up in the chromosomes during fertilisation.

Question 11.
How is equal genetic contribution of male and female parents ensured in the progeny?
Answer:
During sexual reproduction fusion of gametes having haploid set of chromosomes belonging to male and female parents ensure equal contribution.

Question 12.
Only variations that confer an advantage to an individual organism will survive in a population. Do you agree with this statement? Why or why not?
Answer:
Yes. The organism with useful variations will adapt and survive. Moreover they leave behind more offsprings and populations with such genetic variations will survive.

Science Guide for Class 10 PSEB Heredity and Evolution InText Questions and Answers

Question 1.
If a trait A exists in 10% of population of an asexually reproducing species and a trait B exists in 60% of the same population, which trait is likely to have arisen earlier?
Answer:
In asexually reproducing organism trait B originated earlier. The variations in a population are only due to inaccuracies of DNA copying.

Question 2.
How does the creation of variations in a species promote survival?
Answer:
The useful variation in individuals of a species will enable them to adapt according to the changes and new needs. Thus they will enable the survival of species.

Question 3.
How do Mendel’s experiments show that gene may be dominant or recessive?
Answer:
Mendel conducted experiments on garden pea plant selecting seven visible contrasting characters. He selected and crossed homozygous tall pea plant having the genotype TT with a homozygous dwarf pea plant having the genotype tt. Fx generation consists only of tall plants, having genotype Tt. Since they have an allele for dwarfness also, they are all hybrids. The expressed allele T for tallness is dominant over the unexpressed allele t for dwarfness. The fact that the allele for dwarfness is present in the F1 plants can be verified by interbreeding them when F2 progeny will consist of both tall and dwarf plants in the ratio of 3 : 1. On this basis he proposed “Law of Dominance.”

Question 4.
How do Mendel’s experiments proved that traits are inherited indepen dently?
Answer:
Mendel proposed a law on the basis of a dihybrid cross between two homozygous parents. He selected a dominant plant with round and yellow seeds and a recessive plant with wrinkled and green seeds, yields Fx offspring showing the dominant form of both traits, viz. round and yellow. Fx plants, on selling, produce F2 progeny with two parental and two new recombinant phenotypes, that is round yellow: round green: wrinkled yellow: wrinkled green in the ratio of 9 : 3 : 3: 1. This ratio is called Mendel’s dihybrid phenotypic ratio. The factors (genes) of different traits are independent of each other in their distribution into the gametes and in the progeny. This is Mendel’s law of independent assortment.

Question 5.
A man with blood group A married a person with blood group O. Their daughter has blood group O. Is this information enough to tell you which of the blood group trait A or O is dominant. Why or why not?
Answer:
As blood groups is hereditary character, the knowledge of blood groups of parents can give information about the possible blood groups of children and vice-versa.

In this case illustration is as follow :

In the above cross, 50 per cent of progeny will have A blood group and 50 per cent O blood group.
At the same time this data is insufficient. It is not mentioned father has homozygous or heterozygous A blood group. If it is homozygous A then 100 per cent of progeny will have A blood group as Gene IA is dominant over Gene I°.

Question 6.
How is the sex of child determined in human beings?
Answer:
Determination of the sex of child. Sex chromosomes determine sex in human beings. In males, there are 44 +
XY chromosomes, whereas, in female there are 44 + XX chromosomes. Here,
X and Y chromosomes determine sex in the human beings.

Sex determination in man (Note that all the eggs carry X-chromosome but one-half of the sperm carry an X-chromosome and one half carry a Y-chromosome)

Two types of gametes are formed in male, one type is having 50%
X-chromosome, whereas the other type is having Y-chromosome. In female, gametes are of one type and contain X-chromosome.

The females are homogametic. If male gamete having Y-chromosome (androsperm) undergoes fusion with female gamete having X-chromosome the zygote will have XY chromosomes and this gives rise to male child.

If the male gamete having Fig. 9.1. Sex determination in man (Note X-chromosome undergoes fusion with that all the eggs carry X-chromosome but female gamete having X-chromosome, one-half of the sperm carry an the zygote will be having XX-chromosome X-chromosome and one half carry a and this gives rise to female child. Y-chromosome)

Question 7.
What are different ways in which individuals with a particular trait may increase in a population?
Answer:
A particular population with specific traits will increase due to following reasons :

• Sexual reproduction which results into variations.
• Inheritance of variations.
• Natural Selection. The individuals with special traits survive the attack of their predators and multiply while the others will perish.
• Genetic drift provides diversity without any adaptation.

Question 8.
Why are traits acquired during life-time of an individual not inherited?
Answer:
Change in non-reproductive tissue (somatic cells) cannot be passed on to the DNA of germ cells. Thus the acquired trait will die with the death of individual. It is non- heritable and cannot be passed on to its progeny. Changes that occur in DNA of germ cells are inherited.

Question 9.
Why are the small number of surviving tigers is a cause of worry from the point of view of genetics?
Answer:
As the population of tigers is decreasing, there is loss of genes from the gene pool. There cannot be recombinations and variations. Hence no evolution. If number falls suddenly they may become extinct.

Question 10.
What factors could lead to the rise of new species?
Answer:
Factors leading to rise of new species

• Genetic variations
• Mutations
• Natural selection
• Reproductive isolation
• Origin of new species.

Question 11.
Will geographical isolation be a major factor in the speciation by a self- pollinating plant species? Why or why not?
Answer:
No, m self-pollinating species, geographical isolation will not play any role for speciation because the self-pollination is occurring on the same plant.

Question 12.
Will geographical isolation be a major factor in the speciation of an organism that reproduces asexually? Why or why not?
Answer:
No, as there is neither genetic drift nor gene flow play any role during speciation. Moreover asexual reproduction involves single parent and natural geographical barrier can occur between different organisms.

Question 13.
Give an example of characteristic being used to determine how close two species are in evolutionary terms.
Answer:
Homologous organs helps to identify the relationship between organisms. These characteristics in different organisms would be similar because they are inherited from a common ancestor. Example. Fore limbs of mammals having same basic structural plans in birds, reptiles and mammals however the functions get modified in different species.

Question 14.
Can the wing of butterfly and wing of a bat be considered homologous organs? Why or why not?
Answer:
Wings of insects and wings of birds have different basic structural plan and origin. They perform the same function. Thus they are analogous organs and not homologous organs.

Question 15.
What are fossils? What do they tell us about the process of evolution?
Answer:
Fossils are preserved remains, tracks or traces of organisms that lived in the past. Fossils have been found linking all major groups of vertebrates.

Significance of fossils

• Fossils are direct evidence in support of evolution.
• Living forms with simple organization appeared earlier than the complex forms. We can conclude this because fossils of lower layers of the earth are simple as compared to fossils of the upper layers.
• Several forms bearing intermediate characters indicate the transition from an earlier simple to a later complex.
• Fossils of Archaeopteryx serve as a missing link between reptiles and birds. This bird has wings and unlike birds, it had teeth and a long tail.
• On the basis of the fossil records, the complete evolutionary history of present-day horse has been studied.

Question 16.
Why are human beings which look so different from each other in terms of size, colour, and looks are said to be belonging to the same species?
Answer:

• DNA studies have shown that human beings belong to the same species.
• The number of chromosomes is the same.
• All have originated from a common ancestor.
• They interbreed among themselves to produce fertile young ones of their own kind.

Question 17.
In evolutionary terms can we say that which among bacteria, spiders, fish, and chimpanzees have a ‘better’ body design? Why or why not?
Answer:
Chimpanzees have a better body design as compared to the other three mentioned. They are better adapted for locomotion, communication, and thinking.

Punjab State Board PSEB 10th Class Science Book Solutions Chapter 13 Magnetic Effects of Electric Current Textbook Exercise Questions and Answers.

PSEB Solutions for Class 10 Science Chapter 13 Magnetic Effects of Electric Current

PSEB 10th Class Science Guide Magnetic Effects of Electric Current Textbook Questions and Answers

Question 1.
Which of the following correctly describes the magnetic field near a long wire? The field consists of :
(a) straight lines perpendicular to the wire.
(b) straight lines parallel to the wire.
(c) radial lines originating from the wire.
(d) concentric circle centred on the ware.

Answer:
(d) concentric circles centred on the wire (Figure)

Question 2.
The phenomenon of electromagnetic induction is :
(а) the process of charging a body.
(b) the process of generating magnetic field due to a current passing through a coil.
(c) producing induced current in a coil due to relative motion between a magnet and the coil.
(d) the process of rotating the coil of an electric motor.
Answer:
(c) producing induced current in a coil due to relative motion between a magnet and the coil.

Question 3.
The device used for producing electric current is called :
(a) generator
(b) galvanometer
(c) ammeter
(d) motor.
Answer:
(a) generator.

Question 4.
The essential difference between an AC generator and a DC generator is that:
(а) AC generator has an electromagnet while a DC generator has a permanent magnet.
(б) DC generator will generate higher voltage.
(c) AC generator will generate higher voltage.
(d) AC generator has slip rings while the DC generator has a commutator.
Answer:
(d) AC generator has slip rings while DC generator has a commutator.

Question 5.
At the time of short circuit, the current in the circuit.
(a) reduces substantially
(b) does not change
(c) increases heavily
(d) vary continuously.
Answer:
(c) increases heavily.

Question 6.
State whether the following statements are true or false.
(a) An electric motor converts mechanical energy into electric energy.
(b) An electric generator works on the principle of electromagnetic induction.
(c) The field at the centre of a long circular coil carrying current will be parallel straight lines.
(d) A wire with a green insulation is usually the live wire.
Answer:
(a) is false. It converts electric energy to mechanical energy.
(b) is true.
(c) is true.
(d) is false. Green is usually earth wire.

Question 7.
List three sources of magnetic field.
Answer:
Sources of Magnetic field are :

• Magnet.
• Current carrying conductor
• Current carrying solenoid.

Question 8.
How does a solenoid behave like a magnet? Can you determine north and south poles of current carrying solenoid with the help of bar magnet? Explain.
Answer:
Solenoid: It consists of a coil of a number of turns of insulated copper wire closely wound in the shape of a cylinder. Magnetic field around a current carrying solenoid is shown in Figure.

Field lines of the magnetic field inside and around a current carrying solenoid.

These magnetic lines due to current carrying solenoid appear to be similar to that of a bar magnet shown in Figure.

One end [right end] of solenoid behaves like north pole and the other end [left end] behaves like south pole. Magnetic field lines inside the solenoid are in the form of parallel straight lines. This means that the field is the same at all points inside the solenoid.

Field lines around a bar magnet.

A soft iron rod when placed inside the solenoid behaves, like an electromagnet.

Question 9.
When is, the force experienced in a magnetic field, the largest?
Answer:
When the field is perpendicular to current carrying conductor, the force experienced by a current carrying conductor placed in a magnetic field is largest.

Question 10.
Imagine that you are sitting in a chamber with your back to one wall. An electron beam moving horizontally with back towards the front wall, is deflected by a strong magnetic field to your right side. What is the direction of the magnetic field?
Answer:
The magnetic field will be acting in vertically downward direction in accordance with Fleming’s left hand rule. [Direction of the current should be considered in a direction opposite to the direction in which the electrons move].

Question 11.
Draw a labelled diagram of an electric motor. Explain its principle and working. What is the function of a split ring in electric motor?
Answer:
Electric motor: It is a device which is used to convert electric energy into mechanical energy.
Principle, “When a current carrying coil is placed in a uniform magnetic field, it experiences a torque which rotates the coil.”

I indicates direction of current; F the direction field and M the direction of motion

Working: A direct current from a battery is passed through armature. The current flows in the coil along ABCD as shown in Figure (a). The limb AB of the coil experience downward and CD of the coil experience upward force in accordance with Fleming’s left hand rule. These two equal and opposite forces constitute a couple tending to rotate the coil in clockwise direction. After half the rotation, brush B₁ has contact with S₂ and brush B₂ with S₁. The direction of the current gets reversed. The current now flows along DCBA instead of along ABCD. Limb DC experiences downward and BA experiences an upward force in accordance with Fleming’s left-hand rule.

The process repeats itself and motion of armature becomes continuous after some time.
Functions of Split rings. They help in reversing the direction of current in the coil after every half rotation.

Question 12.
Name some devices in which electric motors are used.
Answer:
Electric motor are used in battery operated toys, in tape recorder, in car fans, mixers, grinders, computers and variety of other electric appliances.

Question 13.
A coil of insulated copper wire is connected to a galvanometer. What will happen if a bar magnet is (i) pushed into the coil; (ii) withdrawn from inside the coil; (iii) held stationary in the coil?
Answer:

• When the bar is pushed into the coil, there will be momentary deflection of galvanometer in one direction. This is so because when magnet is brought near the coil, magnetic lines linked with the coil increases, so that induced emf is produced which induces current in the coil.
• Faster, we push the magnet, more will be the deflection.
• When the bar magnet is withdrawn, there will again be momentary galvanometer deflection but in a direction opposite to that when magnet was pushed in. This time also current is induced in the coil.
• When the magnet is held stationary inside the coil, there will be no deflection in galvanometer. It is because no emf is induced and hence no current is induced in the coil.

Question 14.
Two circular coils A and B placed closed to each other. If the current in the coil A is changed, will some current be induced in coil B? Give reason.
Answer:
If the current in the coil is changed (switched on or switched off), then an electric current is induced in coil B. ‘

It is because when, plug in the key is introduced, current flows through the coil ‘A’ so that magnetic field is produced all round it. These magnetic lines produced in the coil ‘A’ will pass through the coil ‘B’ with the result induced emf and hence induced current is produced in the coil ‘B’ which is indicated by deflection of the galvanometer. Now when plug is removed from the key (switched off) the magnetic lines of force Jinked with the coil ‘B’ again change (decreases). This time again current is induced in the coil ‘B’.

Question 15.
When does an electric short circuit occur?
Answer:
Electric short-circuit occurs when :

• live wire incidently touches neutral or earth-wire.
• insulation around the current carrying wires is weak.
• insulation gets hardened by the excessive use.
• current passed through wire is more than its rating.

Question 16.
What is the function of earth wire? Why is it necessary to earth metallic appliances?
Answer:
Earth wire. It is used as a safety measure especially for electric appliance having metallic body. The metallic body of appliances like electric press, fans, toasters, refrigerators etc. are connected to earth wire which provides an easy path for current to go to the earth in case live wire touches the body of appliance incidently. The user will not suffer a severe electric shock in the event of touching a defective appliance.

Question 17.
State two properties of magnetic field lines.
Answer:

1. Magnetic field start from north and end at south.
2. They never intersect each other.

Science Guide for Class 10 PSEB Magnetic Effects of Electric Current InText Questions and Answers

Question 1.
Why does a compass needle get deflected when brought near a bar magnet?
Answer:
A compass needle is a small bar magnet with one end as north and the other end as south pole. It is a well known fact that similar poles repel each other and dissimilar poles attract each other. When N-pole of a bar magnet is brought near the compass, the north pole of compass gets repelled while its S-pole is attracted so that compass needle gets deflected.

Question 2.
Draw magnetic lines around a bar magnet.
Answer:
Place a bar magnet in the middle of a sheet of paper fixed on drawing board by using adhesive tape. Mark the boundary of the magnet with pencil. Place compass near north pole of the magnet when south pole of the compass will point towards north pole of the magnet. Mark the two points a, b at the two ends of the needle. Move the needle to a new position such that S-pole of compass needle is at b [position previously held by N-pole].

Repeat this till you reach south pole of the magnet (Figure).

Drawing magnetic field lines by compass needle.

Now Join the marked points on a paper by a smooth line which gives one magnetic line of force as shown in Figure. Repeat this procedure taking Figure Magnetic field around a bar different starting points.

Magnetic field around a bar magnet.

Question 3.
List the properties of magnetic lines of force.
Or
Write characteristics of magnetic field lines.
Answer:
Properties (characteristics) of magnetic lines of force are :

• These are the closed curves passing through the magnet. Outside the magnet lines of force start from north pole of the magnet and end at the south pole and inside the magnet, the direction of magnetic lines are from south pole to north pole.
• The two magnetic lines of force never intersect each other.
• They have a tendency to contract lengthwise which explains the attraction between opposite poles.
• The tangent at any point of the magnetic lines of force gives the direction of the field at that point.
• They exert lateral pressure upon each other, which explains repulsion between like poles.

Question 4.
Why two magnetic lines of forces never intersect each other?
Answer:
No two magnetic lines of force cross each other because, if they did so, then at the point of intersection; the compass needle would point towards two directions at the same time, which is not possible. Hence two magnetic lines never intersect each other.

Question 5.
Consider a circular loop of wire lying in the plane of the table. Let the current pass through the loop clockwise. Apply right hand rule to find out the direction of the magnetic field inside and outside the loop.
Answer:
The direction of the magnetic field inside and outside loop is as shown in Figure. By applying right hand rule we find that the direction of magnetic field inside the loop is downward normally and outside the loop it is normal to the plane of paper.

Question 6.
The magnetic field in a given region is uniform. Draw a diagram to represent it.
Answer:
Uniform magnetic field is shown by equidistant and parallel lines as shown in Figure If the parallel lines are close to each other, the field is strong. The stronger the field, the closer are the lines.

Question 7.
Choose the correct option.
The magnetic field inside a long straight solenoid carrying current (a) is zero ;
(b) decreases as we move towards end ;
(c) increases as we move towards end;
(d) is same at all the points.
Answer:
(d) is correct. The magnetic field inside a long straight solenoid is same at all the points.

Question 8.
Which of the following property of proton can change while it moves freely in a magnetic field? [There may be more than one correct answer].

(a) mass
(b) speed
(c) velocity
(d) momentum.
Answer:
(c) Velocity and (d) Momentum.

Question 9.
In activity shown, how do you think the displacement of rod AB will be affected :
(i) if the current in rod AB is increased;
Answer:
Since force acting on the rod is directly proportional to the current passing through it. Therefore, the displacement will be increased when current is increased.

(ii) a stronger horse shoe magnet is used;
Answer:
Stronger the magnet, more will be the force and hence the displacement.

(iii) length of the rod AB is increased.
Answer:
Force is also directly proportional to the length of the rod. Hence rod will be displaced more if the length is increased.

Question 10.
A positively charged particle emitted from a nucleus alpha particle projected towards west is deflected towards north by a magnetic field. The direction of the magnetic field is :
(a) towards south
(b) towards east
(c) downward
(d) upward.
Answer:
(d) upward [In accordance with Fleming’s left hand rule]

Question 11.
State Fleming’s left hand rule.
Answer:
Fleming’s left hand rule. It states, “Stretch the thumb, fore finger and middle finger of your left hand such that they are mutually perpendicular to each other. If the first finger points in the direction of magnetic field and central (second) finger points towards the direction of current then thumb points towards the direction of motion as shown in Figure.

Flemmgs left hand rule for direction of force on current carrying conductor

Question 12.
What is the principle of an electric motor?
Answer:
Principle of Electric motor. Electric motor is based upon the principle that when a current carrying coil is placed in a uniform magnetic field, it experiences torque which rotates the coil.

Question 13.
What is the role of the split ring in an electric motor?
Answer:
The split rings act as a commutator in D.C. motor i.e., it reverses the direction of current through the circuit after every half cycle.

Question 14.
Explain different ways to induce current in a coil.
Answer:
There are mainly two methods to induce current in a coil.

Induced current due to relative motion between coil and magnet.

When the magnet is stationary [at rest as in Figure (a)], no induced current is produced.
1. When magnet is moving with its N-pole towards the coil, deflection in galvanometer is as shown in Figure (b). Direction of the current gets reversed when N-pole is withdrawn from inside the coil (going away from coil) as shown in Figure (c). Faster the magnet moves, more is the deflection and hence current in galvanometer.

Deflection produced in the galvanometer needle by the current is same when N-pole was moving down [Figure (6)] or when south pole is out of the coil [Figure (e)].

Current and hence deflection in the galvanometer needle will be again produced if magnet is kept at rest and coil is moved.

2. By changing current in the neighbouring circuit. Take a non¬conducting cylindrical tube (say of card board). Wind two set of coils I and. II on it as shown. Connect a battery and a key to the ends of coil I and a galvanometer to the ends of coil II. When plug is inserted in key K, there will be an instantaneous deflection m galvanometer even though there is no cell in this circuit. Now take out the plug from key K. An instantaneous large deflection in opposite direction to previous deflection will be produced in galvanometer. Thus current has been induced in coil II due to increase or decrease of current in coil I.

Induced Current by changing current m the neighbouring circuit.

Question 15.
State the principle of electric generator.
Answer:
Principle of Electric Gen¬erator. Electric generator is based upon Fleming’s right hand rule.

Right hand rule

Fleming’s right hand rule. Stretch the thumb, fore-finger, control (middle) finger of right hand so that they are perpendicular to each other. If fore-finger indicates the direction of magnetic field, the thumb shows the direction of motion of the conductor, the central (middle) finger will show the direction of induced current.

Question 16.
Name some sources of direct current.
Answer:
Sources of direct current are

• Cell
• Battery
• D.C. generator.

Question 17.
Which sources produce alternating current?
Answer:
Alternating current is produced by A.C. generators. There are hydro-generator and thermal generators.

Question 18.
Choose the correct option :
A rectangular coil of copper wires is rotated in magnetic field. The direction of induced current changes once in each:
(a) two revolutions
(b) one revolution
(c) half revolution
(d) one-fourth revolution.
Answer:
(c) half rotation.

Question 19.
Name two safety measures commonly used in electric circuits and appliances.
Or
Write the two safety measures commonly used in electric circuit appliances.
Answer:
Common Safety Measures used in Electric Circuits. Two most common safety measures used, are :

• A safety fuse of proper rating connected in a circuit prevents damage to the electric appliances and also the circuit due to overloading or short circuiting.
• Earth wire prevents possible electric shock when live wire incidently touches the body of appliance.

Question 20.
An electric oven of 2kW power rating is operated in a domestic electric circuit (220 V) that has a current rating of 5 A. What result do you expect? Explain.
Answer:
Given : Power of oven (P) = 2 kW
= 2,000 W
Voltage (V) =220 volts
Current (I) =?

We know that, P = V x I
or I = \(\frac{\mathrm{P}}{\mathrm{V}}\)
Current (I) = \(\frac{2,000}{200}\)
= \(\frac{100}{11}\)
= 9.09 A

A current of 9.09 A will flow in the circuit. Since the current rating of circuit is 5 A, the fuse (of 5 A) rating if inserted in the circuit will burn up. If no fuse is placed in the circuit, there may be a fire.

Question 21.
What precautions should be taken to avoid the overloading of domestic electric circuits?
Answer:
Precautions to avoid overloading.

• Wires used for carrying current should be of proper current rating. Whereas wire of low current rating may be used for lighting electric bulbs, tubes, T.V. etc., and wires of higher current rating should be used for A.C., heating appliances etc.
• There should be a separate circuit for heating appliance.
• PVC of good quality should be used for insulating wires.
• Each circuit should have a fuse of proper rating.
• After every 3-4 years wires should be replaced by new wires of proper rating.

Punjab State Board PSEB 10th Class Science Book Solutions Chapter 3 Metals and Non-metals Textbook Exercise Questions and Answers.

PSEB Solutions for Class 10 Science Chapter 3 Metals and Non-metals

PSEB 10th Class Science Guide Acids, Bases and Salts Textbook Questions and Answers

Question 1.
Which of the following pairs will give displacement reactions :
(а) NaCl solution and copper metal
(b) MgCl₂ solution and aluminium metal
(c) FeSO₄ solution and silver metal
(d) AgNO₃ solution and copper metal?
Answer:
(d) AgNO₃ solution and copper metal?

Question 2.
Which of the following methods is suitable for preventing an iron frying pan from rusting :
(a) applying grease
(b) applying paint
(c) applying a coating of zinc
(d) all of the above :
Answer:
(c) applying a coating of zinc

Question 3.
An element reacts with oxygen to give a compound with a high melting point. This compound is also soluble in water. The element is likely to be :
(a) calcium
(b) carbon
(c) silicon
(d) iron.
Answer:
(a) calcium

Question 4.
Food cans are coated with tin and not with zinc because :
(а) zinc is costlier than tin
(b) zinc has a higher melting point than tin
(c) zinc is more reactive than tin
(d) zinc is less reactive than tin.
Answer:
(c) zinc is more reactive than tin

Question 5.
You are given a hammer, a battery, a bulb, wires and a switch.
(i) How could you use them to distinguish between samples of metals and non-metals?
(ii) Assess the usefulness of these tests in distinguishing between metals and non-metals.
Answer:
(i) Set up the electric circuit as shown below :

To distinguish between metals and non-metals on the basis of their electrical conductivity.

Insert the sample to be tested between clips A and B
If the bulbs glows, the sample is metal.
If the bulb does not glow, the sample is non-metal.
Thus metals are good conductors of electricity whereas non-metals are poor conductors of electricity.

(ii) If a substance produces a sound when struck beating with a hammer, it is a metal and if no sound is produced, it is a non-metal.
Metals are sonorous whereas non-metals are non-sonorous.

Question 6.
What are amphoteric oxides? Give two examples of amphoteric oxides.
Answer:
Amphoteric oxides. The metal oxide which react both with acids as well as bases to produce salts and water are known as amphoteric oxides.

Examples. Zinc oxide, ZnO Aluminium oxide, Al2O3

Question 7.
Name two metals which will displace hydrogen from dilute acids, and two metals which will not.
Answer:
Zinc and magnesium can displace hydrogen from dilute acids. Copper and silver cannot displace hydrogen from dilute acids.

Question 8.
In the electrolytic refining a metal M, what would you take as the anode, the cathode and the electrolyte?
Answer:
During the electrorefining of metal, the impure metal is made as anode, a thin strip of pure metal M is made as cathode. The electrolyte used a soluble salt of metal M. to be refined.

Question 9.
Pratyush took sulphur powder on a spatula and heated it. He collected the gas evolved by inverting a test tube over it as shown in figure

Collection of Gas
(a) What will be the action of gas on
(i) dry litmus paper?
Answer:
No action.

(ii) moist litmus paper?
Answer:
It turns moist litmus paper red and then bleaches it.

(b) Write a balanced chemical equation for the reaction taking place.
Answer:
S + O₂ → SO₂

Question 10.
State two ways to prevent the rusting of iron.
Answer:
The rusting can be prevented by

1. By painting, oiling, greasing, galvanising, chrome plate or anodising.
2. By forming alloys.

Question 11.
What type of oxides are formed when non-metals combine with oxygen?
Answer:
As they form two types of oxides :
(a) Neutral oxides such as CO, NO etc.
(b) Acidic oxides such as SO₂, CO₂ etc.

Question 12.
Give reasons :
(a) Platinum, gold and silver are used to make jewellery.
Answer:
Platinum, gold and silver are used to make jewellery because these are not attacked by air and moisture. They don’t undergo corrosion and retain their lustre for a long time. Also these metals are malleable and ductile.

(b) Sodium, potassium and lithium are stored under oil.
Answer:
Sodium, potassium and lithium are stored under oil because in contact with moist air containing carbon dioxide, these are covered with a carbonate layer.
e.g. 4Na + O₂ → 2Na₂O
Na₂O + H₂O → 2NaOH
2NaOH + CO₂ → Na₂CO₃ + H₂O

Also they react with water.
e.g. 2Na + 2H₂O → 2NaOH + H₂.
Hence, these metals are stored under oil.

(c) Aluminium is a highly reactive metal, yet it is used to make utensils for cooking.
Answer:
This is due to the reason that a thin sticking oxide layer of aluminium is formed on its surface which prevents further reaction. Also aluminium is a good conductor of heat and the oxide layer (Al₂O₃) is stable even at high temperatures.

(d) Carbonate and sulphide ores are usually converted into oxides during the process of extraction.
Answer:
This is because it is easier to obtain a metal from its oxide as compared to its sulphide and carbonate ore.

Question 13.
You must have seen tarnished copper vessels being cleaned with lemon or tamarind juice. Explain why these sour substances are effective in cleaning the vessels.
Answer:
In tarnished copper vessel there is a layer of basic copper carbonate. This basic layer can be cleaned by using sour substances such as lemon or tamarind juice which are acidic in nature and dissolve the basic coat of copper carbonate

Question 14.
Differentiate betw een metals and non-metals.
Or
Differentiate between metals and non-metals on the basis of their chemical properties.
Answer:
Differences between metals and non-metals :

Metals	Non-Metals
1. They form basic oxides.	1. They form acidic or neutral oxides.
2. They displace hydrogen from dilute acids.	2. They don’t displace hydrogen from dilute acids.
3. Usually they don’t combine with hydrogen. Only a few reactive metals combine with hydrogen to form metal hydroxide which are electrovalent compounds.	3. They react with hydrogen to form hydrides which are covalent compounds.
4. They form chlorides which are electrovalent compounds.	4. They react with chlorine to form chlorides which are covalent compounds.

Question 15.
A man went door to door posing as a goldsmith. He promised to bring back the glitter of old and dull gold ornaments. An unsuspecting lady gave a set of gold bangles to him which he dipped in a particular solution. The bangles sparkled like new but their weight was reduced drastically. The lady was upset but after a futile argument the man beat a hasty retreat. Can you play the detective to find out the nature of the solution he had used?
Answer:
The solution used by goldsmith to bring back the glitter of old and dull gold ornaments was aqua regia. It is a freshly prepared mixture of cone. HCl and cone. HNOg in the ratio 3 : 1. It can dissolve gold,

Question 16.
Give the reasons why copper is used to make hot water tanks but steel (an alloy of iron) is not.
Answer:
This is because iron present in steel reacts with steam to form ferrosoferric oxide whereas copper has no action with water. As a result of it, the body of the steel tank becomes weaker and weaker in case of iron and not in case of copper.

Science Guide for Class 10 PSEB Metals and Non-metals InText Questions and Answers

Question 1.
Give an example of a metal which :
(i) is a liquid at room temperature
Answer:
Mercury

(ii) can be easily cut with a knife
Answer:
Sodium

(iii) it is the best conductor of heat
Answer:
Silver

(iv) is a poor conductor of heat.
Answer:
Lead.

Question 2.
Explain the meaning of malleable and ductile.
Answer:
Malleable: A substance is said to be malleable, if it can be beaten into sheets. e.g. metals are malleable.
Ductile: A substance is said to be ductile, if it can be drawn into wires e.g. the metals are ductile.

Question 3.
Why is sodium kept immersed in kerosene oil?
Answer:
This is because in contact with moist air containing carbon dioxide, it is covered with a carbonate layer.
4Na + O₂ → 2Na₂O
Na₂O + H₂O → 2NaOH
2NaOH + CO₂ → Na₂CO₃ + H₂O

Also sodium reacts with water.
2Na + 2H₂O → 2NaOH + H₂
Hence, sodium is kept immersed in kerosene oil.

Question 4.
Write equation for the reactions of
(i) iron with steam
Answer:

(ii) calcium and potassium with water.
Answer:
Ca + 2H₂O → Ca(OH)₂ + H₂
2K + 2H₂O → 2KOH + H₂

Question 5.
Samples of four metals A, B, C and D were taken and added to the following solution one by one. The results obtained have been tabulated as follows :

Use the table above to answer the following questions about metals, A, B, C and D.
(i) Which is the most reactive metal?
Answer:
B is the most reactive metal.

(ii) What would you observe if B is added to a solution of copper (II) sulphate?
Answer:
B will displace copper from copper sulphate solution.

(iii) Arrange the metals A, B, C and D in the order of decreasing reactivity.
Answer:
The decreasing order of reactivity is B > A > C > D.

Question 6.
Which gas is produced when dilute hydrochloric acid is added to a reactive metal? Write the chemical reaction when iron reacts with dilute H₂SO₄.
Answer:
Hydrogen gas is produced when dilute hydrochloric acid is added to a reactive metal.

Question 7.
What would you observe when zinc is added to a solution of iron (II) sulphate? Write the chemical reaction that takes place.
Answer:
When zinc is added to a solution of iron (II) sulphate it will displace iron from it and light green colour of solution gradually fades away.

Question 8.
(i) Write the electron-dot structures for sodium, oxygen and magnesium.
Answer:
Electron-dot structures for sodium, oxygen and magnesium are

(ii) Show the formation of Na₂O and MgO by the transfer of electrons.
Answer:
Formation of Na₂O:

(iii) What are the ions present in the above compounds?
Answer:

Question 9.
Why do ionic compounds have high melting points?
Answer:
In ionic compounds there are strong electrostatic forces of attraction between oppositely charged ion and a considerable amount of energy is required to break the strong interionic attraction.

Question 10.
Define the terms :
(a) mineral
Answer:
Mineral. The compounds of elements occurring in earth’s crust which are associated with earthly impurities are called minerals.

(b) ore
Answer:
Ore. An ore is a mineral from which metal can be extracted conveniently and economically.

(c) gangue.
Answer
Gangue. The earthly impurities such as sand, lime stone, rocks etc. associated with minerals and ores are collectively known as gangue or matrix.

Question 11.
Name two metals which are found in nature in the free state.
Answer:
Gold and Platinum.

Question 12.
What chemical process is used for obtaining a metal from its oxide?
Answer:
Reduction process.

Question 13.
Metallic oxides of zinc, magnesium and copper were heated with the following metals :

Metal	Zinc	Magnesium	Copper
Zinc oxide
Magnesium oxide
Copper oxide

In which cases will you find displacement reactions taking place?
Answer:
Zinc can displace copper from copper oxide

Magnesium can displace zinc from zinc oxide

Also Mg can displace copper from CuO

Question 14.
Which metals do not corrode easily?
Answer:
The metals which are not attacked by air and moisture don’t corrode easily.

Question 15.
What are alloys?
Answer:
Alloys. These are the homogeneous mixtures of two or more metals or metals and non-metals.

Punjab State Board PSEB 10th Class Maths Book Solutions Chapter 7 Coordinate Geometry Ex 7.3 Textbook Exercise Questions and Answers.

PSEB Solutions for Class 10 Maths Chapter 7 Coordinate Geometry Ex 7.3

Question 1.
Find the area of the triangle whose vertices are:
(i) (2, 3); (- 1, 0); (2, – 4)
(ii) (- 5, – 1); (3, – 5); (5, 2)
Solution:
(i) Let vertices of the ∆ABC are A (2, 3); B(- 1, 0) and C (2, – 4)
Here x₁ = 2, x₂ = – 1 x₃ = 2
y₁ = 3, y₂ = 0, y₃ = – 4 .
∴ Area of ∆ABC = \(\frac{1}{2}\) [x₁ (y₂ – y₃) + x₂ (y₃ – y₁) + x₃ (y₁ – y₂)
= \(\frac{1}{2}\) [2 × (0 + 4) – 1 × (- 4 – 3) + 2 × (3 – 0)]
= \(\frac{1}{2}\) [8 + 7 + 6] = \(\frac{21}{2}\)
= 10.5 sq units.

(ii) Let vertices of the ∆ABC are A (- 5, – 1); B (3, – 5) and C (5, 2)
Here x₁ = – 5, x₂ = 3, x₃ = 5
y₁ = – 1, y₂ = – 5, y₃ = 2
∴ Area of ∆ABC = \(\frac{1}{2}\) [x₁ (y₂ – y₃) + x₂ (y₃ – y₁) + x₃ (y₁ – y₂)]
= \(\frac{1}{2}\) [- 5 (- 5 – 2) + 3 (2 + 1) + 5 (- 1 + 5)]
= \(\frac{1}{2}\) [35 + 9 + 20]
= \(\frac{1}{2}\) × 64 = 32 sq units.

Question 2.
In each of the following find the value of ‘k’ for which the points are coimear.
(i) (7, – 2); (5, 1); (3, k)
(ii) (8, 1); (k, – 4); (2, – 5)
Solution:
(i) Let given points be A (7, – 2); B (5, 1) and C (5, k)
Here x₁ = 7, x₂ = 5, x₃ = 3
y₁ = – 2, y₂ = 1 y₃ = k
Three points are collinear iff
\(\frac{1}{2}\) [x₁ (y₂ – y₃) + x₂ (y₃ – y₁) + x₃ (y₁ – y₂)] = 0
or \(\frac{1}{2}\) [7 (1 – k) + 5(k + 2) + 3(- 2 – 1)] = 0
or 7 – 7k + 5k +10 – 9 = 0
or – 2k + 8 = 0
or – 2k = – 8
or – k = \(\frac{-8}{-2}\) = 4 .
Hence k = 4.

(ii) Let given points be A (8, 1); B (k, – 4) and C(2, – 5)
Here x₁ = 8 x₂ = k, x₃ = 2
y₁ = 1, y = – 4, y = – 5
Three points are collinear iff
\(\frac{1}{2}\) [x₁ (y₂ – y₃) + x₂ (y₃ – y₁) + x₃ (y₁ – y₂)] = 0
or \(\frac{1}{2}\) [8 (- 4 + 5) + k (- 5 – 1) + 2 (1 + 4) = 0]
or 8 – 6k + 10 = 0
or – 6k = – 18 .
or k = \(\frac{-18}{-6}\) = 3.
Hence k = 3.

Question 3.
Find the area of the triangle formed by joining the mid-points of the sides of the triangle whose vertices are (0, – 1), (2, 1) and (0, 3). FInd the ratio of the area of the triangle formed to the area of the given triangle.
Solution:
Let vertices of given triangle ABC are A(0, – 1); B (2, 1) and C (0, 3).
Also, D, E, F be the mid points of AB, BC, CA respectively.
Using mid point formula,
Coordinates of D = \(\left(\frac{0+2}{2}, \frac{-1+1}{2}\right)\) = (1, 0)

Coordinates of E = \(\left(\frac{2+0}{2}, \frac{1+3}{2}\right)\) = (1, 2)

Coordinates of F = \(\left(\frac{0+0}{2}, \frac{3-1}{2}\right)\) = (0, 1)

∴ Co-ordinates of the vertices of DEF are D (1, 0); E (1, 2); F (0,1).
Here x₁ = 1, x₂ = 1, x₃ = 0
y₁ = 0, y₂ = 2, y₃ = 1.
Area of ∆DEF = \(\frac{1}{2}\) [x₁ (y₂ – y₃) + x₂ (y₃ – y₁) + x₃ (y₁ – y₂)]
= \(\frac{1}{2}\) [1 (2 – 1) + 1 (1 – 0) + 0 (0 – 2)]
= \(\frac{1}{2}\) [1 + 1 + 0] = \(\frac{2}{2}\) = 1.

In ∆ABC,
x₁ = 0, x₂ = 2, x₃ = 0
y₁ = – 1, y₂ = 1, y₃ = 3.
Area of ∆ABC = \(\frac{1}{2}\) [x₁ (y₂ – y₃) + x₂ (y₃ – y₁) + x₃ (y₁ – y₂)]
= \(\frac{1}{2}\) [0 (1 – 3) + 2 (3 + 1) + 0 (- 1 – 1)]
= \(\frac{1}{2}\) [0 + 8 + 0] = \(\frac{8}{2}\) = 4
Required ratio = \(\frac{\text { Area of } \triangle \mathrm{DEF}}{\text { Area of } \triangle \mathrm{ABC}}\)
= \(\frac{1}{4}\)

Question 4.
Find the area of the quadrilateral whose vertices taken in order, are (- 4, – 2); (- 3, – 5); (3, – 2); (2, 3).
Solution:
Let co-ordinates of the given quadrilateral ABCD are A(- 4, – 2); B(-3, – 5); C(3, – 2) and D (2, 3).
Join AC then Quad. ABCD divides in two triangles
i.e. ∆ABC and ∆CDA

In ∆ABC
Here x₁ = – 4, x₂ = – 3, x₃ = 3
y₁ = – 2, y₂ = – 5, y₃ = – 2
Area of ∆ABC = \(\frac{1}{2}\) [x₁ (y₂ – y₃) + x₂ (y₃ – y₁) + x₃ (y₁ – y₂)]
= \(\frac{1}{2}\) [- 4 (5 + 2) + (- 3) (- 2 + 2) + 3 (- 2 + 5)]
= \(\frac{1}{2}\) [12 + 0 + 9] = \(\frac{21}{2}\) sq. units.

In ∆CDA
x₁ = 3, x₂ = 2, x₃ = – 4
y₁ = – 2, y₂ = 3, y₃= – 2
Area of ∆CDA = \(\frac{1}{2}\) [x₁ (y₂ – y₃) + x₂ (y₃ – y₁) + x₃ (y₁ – y₂)]
= \(\frac{1}{2}\) [3 (3 + 2) + 2 (- 2 + 2) + (-4) (- 2 – 3)]
= \(\frac{1}{2}\) [20 + 15 + 0] = \(\frac{35}{2}\) sq. units.

Now, Area of quadritateral ABCD = (Area of ∆ABC) + (Area of ∆ACD)
= \(\frac{21}{2}+\frac{35}{2}=\frac{21+35}{2}\)
= \(\frac{56}{2}\) = 28 sq. units.

Question 5.
You have studied in Class IX, (Chapter 9, Q. 3) that a median of a triangle divides it into two triangles of equal areas. Verify this result for ∆ABC whose vertices are A(4, – 6), B(3, – 2) and C(5, 2).
Solution:
Given that coordinates of the vertices of ∆ABC are A(4, – 6); B (3, – 2) and C (5, 2)
Let CD is the median i.e. D is the mid point of AB which divides AABC into two pails i.e.

∆ADC and ∆CDB
Coordinates of D = \(\left(\frac{4+3}{2}, \frac{-6-3}{2}\right)\)
= \(\left(\frac{7}{2}, \frac{-8}{2}\right)\) = (3.5,- 4).

In ∆ADC
x₁ = 4, x₂ = 3.5, x₃ = 5
y₁ = – 6, y₂ = -4, y₃ = 2
Area of ∆ADC = \(\frac{1}{2}\) [x₁ (y₂ – y₃) + x₂ (y₃ – y₁) + x₃ (y₁ – y₂)]
= \(\frac{1}{2}\) [4(—4—2)+3.5(2+6)÷5(—6+4)]
= \(\frac{1}{2}\) [- 24 + 28 – 101]
= \(\frac{1}{2}\) × -6
= 3 sq. units (∵ area cannot be negative).

In ∆CDB
x = 5, x = 35, x = 3
y = 2, y = – 4, y = – 2
Area of ∆CDB = \(\frac{1}{2}\) [x₁ (y₂ – y₃) + x₂ (y₃ – y₁) + x₃ (y₁ – y₂)]
= \(\frac{1}{2}\) [5 (- 4 + 2) + 3.5 (- 2 – 2) + 3 (2 + 4)]
= \(\frac{1}{2}\) [- 10 – 14 + 18]
= \(\frac{1}{2}\) × – 6 = – 3
= 3 sq. units(∵ area cannot be negalive)
From above discussion it is clear that area of ∆ADC = area of ∆CDB = 3 sq. units
Hence, a median of a triangle divides it into two triangles of equal areas.

Punjab State Board PSEB 9th Class Maths Book Solutions Chapter 14 Statistics Ex 14.2 Textbook Exercise Questions and Answers.

PSEB Solutions for Class 9 Maths Chapter 14 Statistics Ex 14.2

Question 1.
The blood groups of 30 students of Class VIII are recorded as follows:
A, B, O, O, AB, O, A, O, B, A, O, B, A, O, O,
A, AB, O, A, A, O, O, AB, B, A, O, B, A, B, O.
Represent this data in the form of a frequency distribution table. Which is the most common, and which is the rarest, blood group among these students ?
Answer:
Frequency distribution table

From the frequency distribution table, it is very clear that the most common blood group is O and the rarest blood group is AB.

Question 2.
The distance (in km) of 40 engineers from their residence to their place of work were found as follows:

Construct a grouped frequency distribution table with class size 5 for the data given above taking the first interval as 0-5 (5 not included). What main features do you observe from this tabular representation?
Answer:
Grouped frequency distribution table

From the frequency distribution table, we can conclude that for the majority of engineers, s i.e., 31 engineers, the distance from their residence to their place to work is 5 km or more than 5 km but less than 20 km. For some engineers, i.e., 5 engineers, this distance is less than 5 km. Still, for some engineers, i.e., 4 engineers, this distance is 20 km or more than 20 km but less than 35 km.

Question 3.
The relative humidity (in %) of a certain city for a month of 30 days was as follows:

(i) Construct a grouped frequency distribution table with classes 84-86, 86 – 88, etc.
Answer:

(ii) Which month or season do you think this data is about ?
Answer:
During 24 days out of 30 days, the relative humidity is 92 % or more than 92 %. This suggests that the data must have been collected during Monsoon.

(iii) What is the range of this data ?
Answer:
Range of the data
= The greatest observation – The least observation
= 99.2 – 84.9
= 14.3

Question 4.
The heights of 50 students, measured to the nearest centimetres, have been found to be as follows:

(i) Represent the data given above by grouped frequency distribution table, taking the class intervals as 160 – 165, 165-170, etc.
Answer:
Grouped frequency distribution table

(ii) What can you conclude about their heights from the table?
Answer:
From the above frequency distribution, we can conclude that the height of 70 % students (35 students) is less than 165 cm while the height of only 10 % students (5 students) is 170 cm or more than that.

Question 5.
A study was conducted to find out the concentration of sulphur dioxide in the air in parts per million (ppm) of a certain city. The data obtained for 30 days is as follows :

(i) Make a grouped frequency distribution table for this data with class intervals as 0.00-0.04, 0.04-0.08, and so on.
Answer:

(ii) For how many days, was the concentration of sulphur dioxide more than 0.11 parts per million?
Answer:
The concentration of sulphur dioxide was more than 0.11 ppm for 8 days (2 + 4 + 2).

Question 6.
Three coins were tossed 30 times simultaneously. Each time the number of heads occurring was noted down as follows:

Prepare a frequency distribution table for the data given above.
Answer:

Question 7.
The value of π up to 50 decimal places is given below:
3.1415926535897932384626433832795028 8419716939937510
(i) Make a frequency distribution of the digits from 0 to 9 after the decimal point.
Answer:
Frequency distribution table

(ii) Which are the most and the least frequently occurring digits?
Answer:
The most frequently occurring digits are 3 and 9 (8 times each) and the least occurring digit is 0 (2 times).

Question 8.
Thirty children were asked about the number of hours they watched TV programmes in the previous week. The results were found as follows:

(i) Make a grouped frequency distribution table for this data, taking class width 5 and one of the class intervals as 5-10.
Answer:

(ii) How many children watched television for 15 or more hours a week?
Answer:
Two children watched television for 15 or more hours a week.

Question 9.
A company manufactures car batteries of a Grouped frequency distribution table particular type. The lives (in years) of 40 such batteries were recorded as follows

Construct a grouped frequency distribution table for this data, using class intervals of size 0.5 starting from the interval 2 – 2.5.
Answer:

Punjab State Board PSEB 9th Class Maths Book Solutions Chapter 14 Statistics Ex 14.1 Textbook Exercise Questions and Answers.

PSEB Solutions for Class 9 Maths Chapter 14 Statistics Ex 14.1

Question 1.
Give five examples of data that you can collect from your day-to-day life.
Answer:
Five examples of data that can be collected from day-to-day life can be given as below:

1. Election results obtained from newspapers or TV
2. The number of different kinds of trees grown in our school.
3. Amounts of invoices of electricity for last one year at our home.
4. The number of students studying in different standards of our school.
5. Percentage of marks scored at last examination by the students in our class.

Question 2.
Classify the data in Q. 1 above as primary or secondary data.
Answer:
Among the five data given as the answer to Q. 1, data no.

Primary data:

• The number of different kinds of trees grown in our school.
• Amounts of invoices of electricity for last one year at our home.
• Percentage of marks scored at last examination by the students in our class.
• primary data which we can collect ourselves.

Secondary data:

• Election results obtained from newspapers or TV
• The number of students studying in different standards of our school.
• Secondary data as they are received from the sources of the newspapers or TV or the office of our school.