# PSEB 9th Class Science Solutions Chapter 2 Is Matter Around Us Pure

Punjab State Board PSEB 9th Class Science Book Solutions Chapter 2 Is Matter Around Us Pure Textbook Exercise Questions and Answers.

## PSEB Solutions for Class 9 Science Chapter 2 Is Matter Around Us Pure

PSEB 9th Class Science Guide Is Matter Around Us Pure Textbook Questions and Answers

Question 1.
Which separation techniques will you apply for the separation of the following?
(a) Sodium chloride from its solution in water.
(b) Ammonium chloride from a mixture containing sodium chloride and ammonium chloride.
(c) Small pieces of metal in the engine oil of a car.
(d) Different pigments from an extract of flower petals.
(e) Butter from curd
(f) Oil from water
(g) Tea leaves from tea
(h) Iron pins from sand
(i) Wheat grains from husk
(j) Fine mud particles suspended in water.
(a) Evaporation
(b) Sublimation
(c) Filtration
(d) Chromatography
(e) Centrifugation
(f) Separating funnel
(g) Filtration
(h) Magnetic separation
(i) Gravity separation
(j) Centrifugation

Question 2.
Write the steps you would use for making tea. Use the words0solution, solvent, solute, dissolve, soluble, insoluble, filtrate and residue.
Step 1: Boil some solvent (water ) in a pan.
Step 2: Put some solute (tea leaves) in a tea pot.
Step 3: Pour the boiling water into the tea pot and let it soak for a few minutes to form a solution.
Step 4: Stir the solution in the tea pot.
Step 5: Take some solute (sugar) into a cup.
Step 6: Filter the above solution obtained in step 4 using strainer and take this solution (filtrate) in the cup. Pour two tea-spoons of milk into the cup and stir it with a spoon. This gives us tea which is ready for drinking. The residue is left on the strainer because these are insoluble whereas sugar and milk are soluble solutes.

Question 3.
Pragya tested the solubility of three different substances at different temperatures and collected the data as given below (results are given in the following table, as grams of substance dissolved in 100 grams of water to form a saturated solution).

 Substances Dissolved Temperature in K 283 293 313 333 353 Potassium nitrate 21 32 62 106 167 Sodium chloride 36 36 36 37 37 Potassium chloride 35 35 40 46 54 Ammonium chloride 2.4 37 41 55 66

(a) What mass of potassium nitrate would be needed to produce a saturated solution of potassium nitrate in 50 grams of water at 313 K?
(b) Pragya makes a saturated solution of potassium chloride in water at 353 K and leaves the solution to cool at room temperature. What would she observe as the solution cools? Explain.
(c) Find the solubility of each salt at 293 K. Which salt has the highest solubility at this temperature?
(d) What is the effect of change of temperature on the solubility of a salt?
(a) Solubility of KN03 in water at 313 K = 62 g / 100 g of water
100 g of water contains KN03 at 313 K = 62 g
∴ 50 g of water will contains KN03 at 313 K = $$\frac{62}{100}$$ × $$\frac{50}{1}$$ = 31 g
∴ Amount of potassium nitrate needed to produce a saturated solution of potassium nitrate in 50 g of water at 313 K = 31 g

(b) On cooling the saturated solution of potassium chloride in water at 353 K to room temperature, the solution will become supersaturated at room temperature and some potassium chloride will settle down.

(c) Solubility of potassium nitrate at 293 K = 32g/100g of water
Solubility of sodium chloride at 293 K = 36g/100g of water
Solubility of potassium chloride at 293 K = 35g/100g of water
Solubility of ammonium chloride at 293 K = 37g/100g of water
Ammonium chloride has highest solubility at 293 K.

(d) (1) If the process of dissolution of salt in water is exothermic, its solubility decreases with the increase in temperature.
(2) If the process of dissolution of salt in water is endothermic, its solubility increases with the increase in temperature.

Question 4.
Explain the following giving examples:
(a) saturated solution
(b) pure substance
(c) colloid
(d) suspension.
(a) Saturated Solution: A solution in which no more of the solute can be dissolved at the given temperature is said to be saturated at that temperature. For example 50 g of NaCl added to 100 ml of water.

(b) Pure substance: A pure substance is made of only one type of atoms or molecules. Pure substances have the same colour, taste, texture at the given temperature and presure. Pure substance has a fixed melting or boiling point at the constant pressure. Pure substance includes elements and compounds. For example, hydrogen gas, sodium chloride, water etc.

(c) Colloid: A substance is said to be in the colloidal state if its particle size lies between 1 to 100 nm. The colloidal solution is heterogeneous and consist of two phases i.e. dispersed phase or colloidal particles and dispersion medium in which colloidal particles are suspended e.g. colloidal solution of starch in water.

(d) Suspension: It is a heterogeneous mixture in which the particles of the solute don’t dissolve but remain suspended throughout the bulk of the material and the size of particles is more than 10-7 m. The particles can be seen with naked eye.

Question 5.
Classify each of the following as a homogeneous or heterogeneous mixture: soda water, wood, air, soil, vinegar, filtered tea.

1. Soda Water – Homogeneous mixture
2. Wood – Heterogeneous mixture
3. Air – Homogeneous mixture
4. Soil – Heterogeneous mixture
5. Vineger – Homogeneous mixture
6. Filtered tea – Homogeneous mixture.

Question 6.
How would you confirm that a colourless liquid given to you is pure water?
Determine the boiling point of the given liquid. If its boiling point is 100°C at 1 atmosphere pressure it is pure water and if boiling point is above 100°C, it is impure water.

Question 7.
Which of the following materials fall in the category of a “pure substance”?
(a) Ice
(b) Milk
(c) Iron
(d) Hydrochloric acid
(e) Calcium oxide
(f) Mercury
(g) Brick
(h) Wood
(i) Air
(a) Ice
(b) Iron
(c) Hydrochloric acid
(d) Calcium oxide
(f) Mercury

Question 8.
Identify the solutions among the following mixtures:
(a) soil
(b) sea water
(c) air
(d) coal
(e) soda water
(b) sea water
(c) air and
(e) soda water

Question 9.
Which of the following will show “Tyndall effect”?
(a) Salt solution
(b) Milk
(c) Copper sulphate solution
(d) Starch solution.
(b) Milk and (d) Starch solution because these are colloidal solutions.

Question 10.
Classify the following into elements, compounds and mixtures:
(a) sodium
(b) soil
(c) sugar solution
(d) silver
(e) calcium carbonate
(f) tin
(g) silicon
(h) coal
(i) air
(j) soap
(k) methane
(l) carbon dioxide
(m) blood
(a) Sodium – Element
(b) Soil – Mixture
(c) Sugar solution – Mixture
(d) Silver – Elemei
(e) Calcium carbonate – Compound
(f) Tin – Element
(g) Silicon – Element
(h) Coal – Mixture
(i) Air – Mixture
(j) Soap – Mixture
(k) Methane – Compound
(l) Carbon dioxide – Compound
(m) Blood – Mixture

Question 11.
Which of the following are chemical changes?
(a) Growth of a plant
(b) Rusting of iron
(c) Mixing of iron filings and sand
(d) Cooking of food
(e) Digestion of food
(f) Freezing of water
(g) Burning of a candle.
(a) Growth of a plant
(b) Rusting of iron
(d) Cooking of food
(e) Digestion of food
(f) Burning of a candle.

Science Guide for Class 9 PSEB Is Matter Around Us Pure InText Questions and Answers

Question 1.
What is meant by a pure substance?
It is a material containing particles of only one kind having a definite set of properties. Pure substances include elements and compounds.

Question 2.
List the points of differences between homogeneous and heterogeneous mixtures.

 Homogeneous mixture Heterogeneous mixture 1. It consists a single phase. 2. It has a uniform composition throughout. 3. It has the same properties throughout the bulk. 4. There are no visible boundaries between its components. 5. Examples: Sodium chloride dissolved in water, ethyl alcohol dissolved in water. 1. It consists two or more phases. 2. It does not have a uniform composition thoughout. 3. It does not have same properties throughout the bulk. 4. There are visible boundaries of separation between its components. 5. Examples: Air, gun powder, iron filings, sand and sulphur.

Question 3.
Differentiate between homogeneous and heterogeneous mixtures with examples.
Same as given above.

Question 4.
How are true solution, colloidal solution and suspension different from each other?

 Property True Solution Colloidal solution Suspension 1. Nature Homogeneous Heterogeneous Heterogeneous 2. Particle size Less than 1 am 1 to 100 nm More than 100 nm 3. Diffusion Diffuse rapidly Diffuse slowly Don’t diffuse 4. Filtrability Paritcles can pass through ordinary filter paper as well as semipermeable membrane Particles can pass through ordinary filter paper but not through semi-per­meable membrane Particles can’t pass through filter paper as well as semi­permeable mem­brane 5. Appearance Clear and transparent Generally clear and transparent Opaque 6. Tyndall effect Don’t show Show May or may not show 7. Visibility Particles are not visible Particles can be seen only with ultrami­croscope Particles can be seen with naked eye or microscope.

Question 5.
To make a saturated solution, 36 g of sodium chloride is dissolved in 100 g of water at 293 K. Find its concentration at this temperature.
Mass of sodium chloride (solution) = 36g
Mass of water (solvent) = 100g
Total mass of solution = 100 + 36 = 136g
Mass percentage of solution = Mass of solute / Mass of solution × 100
= 36 / 136 × 100
= 26.47

Question 6.
How will you separate a mixture containing kerosene and petrol (difference in their boiling points is more than 25°C), which are miscible with each other?
By distillation.

Question 7.
Name the technique to separate:

1. Butter from curd
2. Salt from seawater
3. Comphor from salt.

1. By centrifugation.
2. By evaporation.
3. By sublimation.

Question 8.
What types of mixture are separated by the technique of crystallisation?
The mixtures in which the substance is soluble in a suitable hot solvent whereas the impurities are insoluble.

Question 9.
Classify the following as chemical or physical changes:
(a) cutting of trees.
(b) melting of butter in a pan.
(c) rusting of almirah.
(d) boiling of water to form steam.
(e) passing of electric current through water and the water breaking down into hydrogen and oxygen gases.
(f) dissolving common salt in water.
(g) making a fruit salad with raw fruits.
(h) burning of paper and wood.
(a) Cutting of trees-Chemical change
(b) Melting of butter in a pan-Physical change
(c) Rusting of almirah-Chemical change
(d) Boiling of water to form steam-Physical change
(e) Passing of electric current through water and the water breaking down into hydrogen and oxygen gases-Chemical change
(f) Dissolving common salt in water-Physical change
(g) Making a fruit salad with raw fruits-Chemical change
(h) Burning of paper and wTood- Chemical change

Question 10.
Try segregating the things around you as pure substances or mixtures.
Some examples are:

1. Water – Pure substance
2. Milk – Mixture
3. LPG – Mixture