PSEB Notes

This PSEB 8th Class Science Notes Chapter 15 Some Natural Phenomena will help you in revision during exams.

PSEB 8th Class Science Notes Chapter 15 Some Natural Phenomena

→ Sparks, in the sky, was believed to be the wrath of God.

→ In 1752, Benjamin Franklin established that lightning and the spark of amber were the same things.

→ Electricity is responsible for sparks or lightning in the sky.

→ Rubbing produces electric charges in some materials.

→ Similar materials acquire the same charges when rubbed with the same materials.

→ Like charges repel each other.

→ Different materials acquire different charges when rubbed with the same materials or different materials.

→ Unlike charges attract each other.

→ Two kinds of changes are positive and negative.

→ The electric charge generated by rubbing is called static electricity.

→ Static charges are stationary i.e. they do not move.

→ Moving charge constitutes an electric current.

→ Earthing is the process of transfer of charges from a charged object to the earth. Lightning is nothing but an electric discharge.

→ Electric discharge occurs when

• two clouds come together
• clouds come near the earth surface
• clouds and the human body come closer

→ Clouds carry -ve charges on them and on coming in contact with +ve charge produce a huge amount of energy in form of bright light and sound.

→ A house or a building and even a closed vehicle is the safest place during a thunderstorm.

→ A lightning conductor is a device to secure tall buildings from the effect of lightning.

→ Electric cell emits electric discharge, which can be up to 650 volts.

→ Thunderstorms, cyclones, lightning are natural phenomena that cause large-scale destruction of human life and property.

→ Earthquake is also a natural phenomenon.

→ Predictions about thunderstorms, cyclones, and lightning can be done, but earthquakes can not be predicted.

→ An earthquake is the sudden shaking or trembling of the earth.

→ Floods, Landslides, Tsunami are caused by earthquakes.

→ A seismograph is an instrument meant to record seismic waves produced on the surface of the earth by tremors.

→ The intensity of an earthquake is measured in terms of magnitudes on a scale called the Richter Scale.

→ Symmetrical and mud/timber buildings are to be constructed in seismic-prone areas.

→ Static Electricity: The electrical charge excited by rubbing is said to be static electricity.

→ Earthing: The process of transfer of charges from a charged body to the earth is called earthing.

→ Electric Discharge: The process of producing light and sound by clouds is called electric discharge.

→ Thunderstorm: A loud noise produced across the sky during a rainy day is called a thunderstorm.

→ Lightning: A bright light produced across the sky, due to the rubbing of two clouds or clouds and earth, is lightning.

→ Earthquake: The disturbance deep inside the earth’s crust that causes trembling and shaking of the earth, is called an earthquake.

→ Lightning Rod: It is a device to secure tall buildings from the effect of lightning.

This PSEB 8th Class Science Notes Chapter 14 Chemical Effects of Electric Current will help you in revision during exams.

PSEB 8th Class Science Notes Chapter 14 Chemical Effects of Electric Current

→ Some materials that allow current to pass through them are called conductors and some that do not allow the current to pass through them are called insulators.

→ Some liquids that allow an electric current to pass through them, are called electrolytes.

→ An electric bulb glows, when an electric current passes through it.

→ LEDs are used, when the electric current is very small.

→ Pure air is an insulator.

→ Tap water, saltwater, sea or pond water all conduct electricity as they contain impurities and salt them.

→ Pure distilled water is a non-electrolyte.

→ Solutions of acids, bases, and salts are good electrolytes.

→ The passage of an electric current through a conducting solution causes chemical reactions.

→ Evolution of gas, change of color of the solution, and deposits of metal on electrodes are a few examples of chemical effects of electric current.

→ Fruits and vegetables can also conduct electricity.

→ Passing an electric current through acidulated water produces bubbles of oxygen and hydrogen on +ve and -ve terminals respectively.

→ Electroplating is an important application of the chemical effect of electric current.

→ Electroplating is the process of depositing a layer of any desired (superior) metal on another metallic object (of base metal) by means of electricity.

→ Electroplating is very useful to obtain shiny and rust-proof articles by covering cheap metals with desired coatings of costlier metals.

→ Conductors: Materials that allow current to pass through them, are called conductors.

→ Insulators: Materials that do not allow current to pass through them, are called insulators.

→ Electrolysis: It is the process by which a substance (electrolyte) is decomposed into its basic components by passing an electric current through it.

→ Anode: The electrode, which is connected to the positive end of the battery is called the anode.

→ Cathode: The electrode, which is connected to the negative end of the battery is called the cathode.

→ Electrolyte: A salt solution that conducts electricity through it.

This PSEB 8th Class Science Notes Chapter 13 Sound will help you in revision during exams.

PSEB 8th Class Science Notes Chapter 13 Sound

→ Sound is produced by a vibrating object.

→ The maximum distance to which a vibrating body moves on either side from its mean position is called the amplitude of vibration.

→ The time taken to complete one oscillation is called the time period.

→ The number of oscillations per second is called the frequency of oscillation.

→ Frequency is measured in hertz (Hz).

→ The larger the amplitude of vibration, the louder is the sound produced.

→ The higher the frequency of vibration, the higher is the pitch.

→ For human ears, the audible range of frequency is 20 Hz to 20000 Hz.

→ Sound needs a medium for its propagation. It cannot travel in a vacuum.

→ Light travels much faster than sound.

→ The sound may get reflected by an obstacle. The echo is produced due to reflected sound.

→ Some surfaces reflect sound better than others.

→ The pleasant effect of sound on the ear is called music while the unpleasant sound is called noise.

→ In human beings, voice is produced by the vibration of their vocal cords.

→ Amplitude: The maximum distance through which a vibrating body is displaced from its mean position.

→ Echo: The reflection of sound from an obstacle such as a building or a mountain.

→ Frequency: The number of vibrations made by a vibrating body in 1 second.

→ Hertz (Hz): The unit of frequency.

→ Larynx: Organ of voice in human beings.

→ Loudness: The property of sound which depends upon the amplitude and intensity of the vibrating body.

→ Musical Sound: Sound which produces a pleasing effect on the ear.

→ Noise: Sound which produces a disagreeable effect on the ear.

→ Ultrasonic: Vibrations having a frequency above 20,000 Hz.

→ Vibrating Body: An object, moving to and fro about the mean position.

→ Vibrations: To and fro motion of an object.

→ Vocal Cords: Two pairs of membranous cords or folds in the larynx.

This PSEB 8th Class Science Notes Chapter 12 Friction will help you in revision during exams.

PSEB 8th Class Science Notes Chapter 12 Friction

→ Force opposing the motion of the body is called the force of friction.

→ Force of friction acts between any two surfaces in contact with each other.

→ Friction depends upon the nature and smoothness of the surface.

→ Friction is due to irregularities on the two surfaces in contact.

→ Friction increases with pressure.

→ Sliding friction is less than static friction.

→ Friction is both a friend and a foe.

→ Friction is a necessary evil.

→ Friction can be increased or decreased as per requirement.

→ Wheels reduce friction.

→ Lubricants are substances that can reduce friction.

→ The frictional force exerted by fluids is also known as drag.

→ Frictional force in fluids depends upon the speed, nature of the object, and shape of the object.

→ Streamlined objects offer less friction in fluids.

→ Friction: A force which opposes the relative motion between the two surfaces in contact is called friction.

→ Static Friction: A force that counterbalances the applied force on a body is static friction.

→ Sliding Friction: A force that exists between any two sliding surfaces is sliding friction.

→ Rolling Friction: A friction that comes into play between two rolling materials is called rolling friction.

→ Fluid Friction: A force exerted by the fluid on the object immersed in it, is called fluid friction.

→ Streamline: A particular shape that offers little resistance in air or water.

→ Fluids: The name given to air and liquids together.

This PSEB 8th Class Science Notes Chapter 11 Force and Pressure will help you in revision during exams.

PSEB 8th Class Science Notes Chapter 11 Force and Pressure

→ Force is a push or a pull that produces or tends to produce a change in the state of a body.

→ The effect of force depends not only on the magnitude of force but also depends on the area on which it is applied.

→ Force can change the speed, the direction of motion, and the shape of an object,

→ There are various types of forces such as muscular, magnetic, electrostatic, gravitational, and frictional.

→ Force acting per unit area is called pressure.

→ Liquids and gases apply pressure on the surfaces of the container.

→ The atmosphere also exerts pressure, called atmospheric pressure.

→ The pressure exerted by liquids at a given depth is equal in all directions.

→ The pressure of a column of liquid depends on its depth. The more the depth of the liquid column, the more is the pressure.

→ Gases exert pressure in all directions.

→ Force: It is defined as an external cause that changes or tends to change the state of rest or of uniform motion of an object. It is a vector quantity.

→ Resultant Force: When two or more forces act on a body simultaneously, then a single force that produces the same effect as the combined effect of all the forces together, is called resultant force.

→ The force of Friction: The force which opposes the motion of one body over another body in contact with it, is called the force of friction or simply friction.

→ Gravitation: Gravitation is the attraction between any two bodies (particles) in the universe.

→ Weight: The weight of a body is the force with which the body is attracted towards the centre of the earth.

→ Pressure: Force acting per unit area is called pressure.

→ Atmospheric Pressure: Pressure exerted by the atmosphere on all the objects lying on the earth is called atmospheric pressure.

This PSEB 8th Class Science Notes Chapter 10 Reaching the Age of Adolescence will help you in revision during exams.

PSEB 8th Class Science Notes Chapter 10 Reaching the Age of Adolescence

→ It is after growing up to a certain age that human beings and other animals become capable of reproduction.

→ On crossing the age of 10 or 11 in human beings there is a sudden spurt in growth.

→ Growth is a natural process.

→ The period of life when the body undergoes changes, leading to reproduction maturity is called adolescence.

→ Adolescence begins at the age of 11 and lasts upto 18 or 19 years of age.

→ Adolescents are also called teenagers.

→ The human body undergoes severe changes during adolescence which marks the onset of puberty.

→ The most conspicuous change during puberty is height.

→ The rate of growth in height varies in different individuals.

→ All the body parts do not grow at the same rate.

→ Height also depends on the genes inherited from parents.

→ At puberty, the voice box begins to grow. Generally, girls have a high-pitched voice, whereas the voice in boys is deep.

→ During puberty, the secretion of sweat glands and sebaceous glands also increases.

→ Endocrine glands release hormones directly into the bloodstream.

→ Adolescence is also a period of change in a person’s way of thinking.

→ The appearance of secondary sexual characters helps in distinguishing males from females.

→ Changes occurring in adolescence are controlled by hormones which are the chemical substances secreted by endocrine glands.

→ Hormones are secreted by endocrine or ductless glands.

→ The endocrine glands are the pituitary, adrenal, thyroid, and gonads.

→ The pancreas is an exocrine as well as an endocrine gland.

→ Pheromones are the hormones present in insects.

→ An endocrine gland does not have a duct and is, therefore, also called a ductless gland.

→ A ductless or endocrine gland pours its secretion into the circulatory system of the body for sending to the target cells.

→ Secretions of endocrine glands are called hormones.

→ Testes or male gonads are mixed organs that produce sperms as well as male sex hormones or androgens (e.g., testosterone, androsterone).

→ Ovary secretes estrogen and progesterone hormones.

→ The cyclic changes that occur every 28 days (lunar month) in the reproductive tract of human females from the period of puberty to the age of menopause are called the menstrual cycle.

→ At the age of 45-50 women stop menstruation. It is called menopause.

→ There are 23 pairs of chromosomes in humans.

→ There are 22 pairs of autosomes and 1 pair of sex chromosomes in human beings.

→ The change from larva to adult is called metamorphosis. These changes are also controlled by hormones.

→ The physical and mental well-being of an individual is regarded as an individual’s health.

→ Diet for an adolescent has to be carefully planned as it is a stage of rapid growth and development.

→ Personal hygiene is more necessary for teenagers because the increased activity of sweat glands makes the body smelly.

→ All adolescents should take walks, do exercise and play other games.

→ Adolescence: Children between the ages of 10 or 11 years to 18 or 19 years are called adolescents. This period of the age is called adolescence.

→ Puberty: It is a period (11 to 18 years) when the reproductive organs start functioning.

→ Voice Box: It is a box consisting of cartilages present in the throat of human beings causing voice.

→ Adam’s Apple: In boys, the growing voice box is seen as a protruding part of the throat called Adam’s apple.

→ Secondary Sexual Characters: In boys and girls some characters are present which helps to distinguish them. These are called secondary sexual characters.

→ Endocrine Glands: The ductless glands present in animals which secrete hormones and pour them directly into the bloodstream are called endocrine glands.

→ Hormones: These are the chemical secretions secreted by endocrine glands to control the activities of the human body.

→ Target Site: It is a particular body part where hormones released by the endocrine glands through the bloodstream reach.

→ Pituitary Gland: It is a master gland present in the brain.

→ Testosterone: It is a male hormone secreted by the testes at the onset of puberty.

→ Estrogen: It is a female hormone released by the ovaries at the onset of puberty which makes the breasts develop.

→ Sex Chromosomes: Human beings have 23 pairs of chromosomes. One pair out of them (23rd pair) is called a sex chromosome.

→ Thyroxine: It is a hormone secreted by the thyroid gland situated in the neck.

→ Insulin: It is a hormone secreted by the pancreas which controls sugar levels in the blood.

→ Adrenalin: It is a hormone secreted by the adrenal gland which maintains the salt balance in the blood.

→ Balanced Diet: A diet that contains the various components of food (carbohydrates, fats, proteins, minerals, vitamins, water) in the right proportion.

→ Health: The physical and mental well-being of an individual is regarded as an individual’s health.

This PSEB 8th Class Science Notes Chapter 9 Reproduction in Animals will help you in revision during exams.

PSEB 8th Class Science Notes Chapter 9 Reproduction in Animals

→ Reproduction ensures the continuation of similar kinds of individuals, generation after generation.

→ All living organisms reproduce to create more of their own kind. This process is called reproduction.

→ There are two main methods of reproduction.

• Asexual reproduction
• Sexual reproduction

→ In asexual reproduction, a new individual is formed from a single parent.

→ Living organisms reproduce asexually by the following five methods:

• Binary fission
• Budding
• Spore formation.
• Vegetative reproduction
• Regeneration

→ In sexual reproduction, two parents are needed to produce new individuals.

→ The male parent produces male gametes and the female parent produces female gametes.

→ The union of male and female gametes is known as fertilization.

→ There are some organisms in which both the gametes exist in the same individual. Such organisms are called hermaphrodites.

→ The fertilization in some animals is internal and in others external.

→ The process of forming specific shapes and patterns and increasing in size is called development and growth.

→ The growth of parts involves changes in shape, size, and number of constituents.

→ In plants the growth is indefinite but in animals it is definite.

→ The process of formation of the individual from seed, zygote, or body part is called development.

→ There are different ways for the development of individuals.

→ Sexual reproduction is highly evolved.

→ Male Reproductive System consists of a pair of testes, two epididymis, two vasa differentia, accessory glands, two ejaculatory ducts, urethra, and a copulatory organ or penis. Except for testes, all others are secondary male sex organs.

→ The female Reproductive System is made up of a pair of ovaries, a pair of oviducts, uterus, vagina, external genitalia, accessory genital glands, and mammary glands. Except for the first, all others are secondary female sex organs.

→ Semen is a milky fluid produced by the male reproductive system and ejaculated during orgasm.

→ It contains spermatozoa and secretions of glands (seminal vesicles, prostate gland, and Cowper’s glands).

→ The penis is the male copulatory organ that also takes part in the conduction of urine from the body.

→ Spermatazoan (Sperm) is a motile, microscopic male gamete.

→ A typical spermatozoan consists of 4 parts – head, neck, middle piece, and tail.

→ Cloning is the production of an identical cell, carries another living part of a complete organism.

→ The cloned animals are found to be born with severe abnormalities.

→ Sexual Reproduction: A kind of reproduction in which the union of two opposite sexes (male and female) accomplishes fertilization is called sexual reproduction.

→ Asexual Reproduction: A kind of reproduction in which new ones are produced from a single parent is called asexual reproduction.

→ Egg: It is a female gamete produced by the ovary of a female.

→ Sperms: These are male gametes that are produced by the testes of males.

→ Fertilization: The union of male gamete (sperm) and female gamete (egg or ovum) is called fertilization.

→ Zygote: A single-celled structure formed by the union of sperm and egg is called a zygote.

→ Internal Fertilization: Fertilization that takes place inside the body of a female body is known as internal fertilization.

→ External Fertilization: Fertilization that takes place outside the body of females is called external fertilization.

→ Embryo: The zygote divides repeatedly into a structure called an embryo.

→ Foetus: The stage of development of an embryo in which all the body parts are identifiable is called foetus.

→ Viviparous Animals: The animals which produce young ones are known as viviparous animals.

→ Oviparous Animals: The egg-laying animals are known as oviparous animals.

→ Metamorphosis: The drastic change which transforms a larva into an adult is called metamorphosis.

→ Budding: The kind of asexual reproduction in which a new individual develops from the buds is called budding.

→ Binary Fission: A kind of asexual reproduction in which two individuals are produced simply by dividing itself is called binary fission.

→ Cloning: Cloning is the production of an exact copy of a cell or a complete organism.

This PSEB 8th Class Science Notes Chapter 8 Cell Structure and Functions will help you in revision during exams.

PSEB 8th Class Science Notes Chapter 8 Cell Structure and Functions

→ All living things carry out certain basic functions.

→ Roots, stems, leaves, and flowers are the organs of plants.

→ Animals have also parts such as hands, feet, legs, etc.

→ You cannot observe small pores in your skin without the help of a magnifying lens.

→ All living organisms take and digest food, respire, and excrete waste products.

→ Each organism represents an individual of its own kind.

→ Cells in living organisms are complex structures unlike bricks in a building.

→ Cells found in living organisms show a variety of numbers, shapes, and sizes.

→ Single-celled organisms like Amoeba, Paramecium, and Bacteria are called unicellular organisms.

→ Cells in multicellular plants and animals have a variety of shapes. Cells are generally round or spherical in shape.

→ The yellow part of the hen’s egg is called yolk and it is surrounded by white albumen, yellow yolk represents a single cell.

→ All cells are bounded by a membrane called plasma membrane or cell membrane.

→ Plasma membrane encloses a liquid substance known as protoplasm.

→ The cell wall is present in plant cells which are made up of cellulose.

→ Both the plasma membrane and cell wall give shape to the cell.

→ Ostrich egg represents the largest cell visible to the unaided eye.

→ Each cell has smaller components called cell organelles.

→ Cell multiplies and organisms become multicellular and grow in size.

→ Cells in the living organism are basic structural units.

→ Different groups of cells perform a variety of functions.

→ The number of cells being less in smaller organisms does not affect the functioning of the organisms.

→ WBC in human blood is also single-celled.

→ A group of cells performing a definite function is called a tissue.

→ Each organ is made up of a number of tissues.

→ Organ: These are the smaller parts of all living organisms. Each organ is made up of a number of tissues.

→ Tissue: A group of cells performing a definite function is called a tissue.

→ Cell: It is the basic structural and functional unit of all living organisms.

→ Unicellular: Some living organisms are made up of only a single cell that performs all the metabolic functions. Such organisms are called unicellular.

→ Multicellular: Some organisms are made up of a number of cells. Such organisms are called multicellular. In these organisms, different cells perform different functions.

→ Pseudopodia: These are finger-like false feet of amoeba.

→ White Blood Cell (WBC): These are some of the components of blood cells that engulf harmful foreign materials. These are single-celled.

→ Cell Membrane or Plasma Membrane: It is a thin covering present outside the cell which gives shape to it.

→ Cytoplasm: It is a liquid portion present between the cell membrane and nucleus of a cell.

→ Organelles: These are the living components of cells present in their cytoplasm.

→ Cell Wall: It is an extra covering present around the cell membrane of only plant cells. It gives shape and rigidity to the cell.

→ Nucleus: It is the round part of the cell which is called the controlling centre of the cell.

→ Nucleolus: It is a component of the nucleus which is dense and has a spherical body.

→ Nuclear Membrane: The nucleus is separated from the cytoplasm by a membrane called the nuclear membrane.

→ Prokaryotes: The organisms whose cells are without a well-organized nucleus i.e. lacking nuclear membrane are called prokaryotes.

→ Eukaryotes: The organisms whose cells have a distinct and clear nucleus bounded by the nuclear membrane are called eukaryotes.

→ Vacuole: The fluid-filled organelles present in a cell are called vacuoles.

→ Plastids: Small coloured bodies present in plant cells only are called plastids.

→ Chloroplasts: Green plastids present in plant cells are called chloroplasts.

→ Gene: Genes are dot-like structures present on chromosomes that help in the inheritance of characters from parents to the next generation.

→ Chromosome: These are thread-like structures present in the nucleus of a cell.

This PSEB 8th Class Science Notes Chapter 7 Conservation of Plants and Animals will help you in revision during exams.

PSEB 8th Class Science Notes Chapter 7 Conservation of Plants and Animals

→ These days the forests are being cut down and that land is used for other purposes.

→ Some natural causes of deforestation have been forest fires and severe drought.

→ Deforestation increases the temperature and pollution on the earth. It disturbs the balance in nature.

→ Deforestation also leads to global warming, change in soil properties, results in soil erosion, leads to a decrease in water holding capacity of the soil.

→ The government has framed rules, methods, and policies to protect and conserve plants and animals in forests.

→ The biosphere is that part of the earth where organisms live or which supports life.

→ Biodiversity can be defined for a specified geographical region, or for the entire biosphere.

→ Biosphere reserves are the areas meant for the conservation of biodiversity.

→ The plants and animals found in a particular area are known as flora and fauna respectively of that area.

→ A species is a group of populations that are capable of interbreeding with each other.

→ The areas where wild animals are protected and preserved area known as wildlife sanctuaries.

→ It provides protection and suitable living conditions to wild animals.

→ Sometimes the protected forests are not safe because the people living in the neighbourhood encroach upon them and destroy them.

→ National parks preserve flora, fauna, landscape, and historical objects of an area.

→ The forest teak of India is found in Satpura National Park.

→ Project Tiger was launched on 1st April 1973 by our government to protect the tigers of our country.

→ Endangered animals are those which are facing extinction.

→ The ecosystem consists of plants, animals, and micro-organisms in an area alongwith non-living components.

→ Red Data Book is a book that keeps a record of all the endangered animals and plants.

→ Migratory birds fly too far away from specific areas every year during a particular time because of climatic changes.

→ Paper is one of the important products we get from forests. So we should save paper.

→ Reforestation is the restocking of the destroyed forests by planting new trees.

→ Biodiversity: It refers to the variety in life existing on earth, their interrelationships, and their relationships with the environment.

→ Deforestation: Cutting and clearing trees on a large scale is called deforestation.

→ Desertification: The conversion of fertile land into the desert is called desertification.

→ Ecosystem: The relationship between a living community and its non-living environment is known as an ecosystem.

→ Reforestation: It is the restocking of the destroyed forests by planting new trees.

→ Endangered Species: The species which are facing the danger of extinction are called endangered species. e.g. Leopard, Wild dog, etc.

→ Fauna: The animals found in a particular area constitute the fauna of that area.

→ Red Data Book: A book that contains a record of all the endangered species is called a red data book.

→ Endemic Species: These are exclusively found in a particular area only which may be any geographical unit.

→ Flora: The plants found in a particular area constitute the flora of that area.

→ Extinct: It means the disappearance of the species from the earth.

→ Migration: Going far away from the original habitat of some species during a particular period of the year is called migration.

→ Sanctuaries: These are the places where killing or capturing any animal is strictly prohibited.

→ National Parks: These are the reserves or places which preserve flora, fauna, landscape, and historical objects of an area.

→ Biosphere Reserves: It is a specified area in which multiple uses of land is permitted by dividing it into certain zones and each zone is specified for a particular activity.

This PSEB 8th Class Science Notes Chapter 6 Combustion and Flame will help you in revision during exams.

PSEB 8th Class Science Notes Chapter 6 Combustion and Flame

→ Fuels of different varieties are used for various purposes.

→ Fuels are used in homes, industries, automobiles.

→ Cowdung, wood, coal, charcoal, petrol, diesel, natural gas. L.P.G. etc. is various fuels.

→ Some fuels burn with flame and some do not give a flame on burning.

→ Combustion is a chemical process in which a substance reacts with oxygen to give off heat and light.

→ Fuel is a substance that gives off heat and light on burning.

→ Food is fuel to one’s body.

→ Fuels can be classified into solid, liquid, or gas fuels.

→ The substance which can burn to give light and heat are called combustible substances.

→ The non-combustible substance cannot react with oxygen on burning and cannot give light or heat.

→ Wood, Paper, Kerosene oil, Straw, Charcoal, Match sticks are combustible substances.

→ Iron nails, stone pieces, glass, etc. are non-combustible substances.

→ The lowest temperature at which a substance catches fire is called its ignition temperature.

→ The burning of various combustible materials requires different temperatures.

→ Inflammable substances are those substances that have very low ignition temperature and they easily catch fire with a flame.

→ Petrol, Diesel, LPG, alcohol are a few examples of inflammable substances.

→ Forest fire is very harmful.

→ Oxygen is necessary for combustion.

→ Three requirements for producing fire are:

• Presence of oxygen
• Presence of combustible substance
• Minimum ignition temperature of the substance

→ To control fire, one of the requirements for combustion is to be removed.

→ Water is mainly used to control fire as it lowers the ignition temperature.

→ Oil or petrol fire cannot be controlled by water as water is heavier than oil, it gets settle down below the oil and oil continues to burn.

→ Being a good conductor of electricity water is also not used in case of fires produced by short-circuiting.

→ Sand/soil is used to control fires caused by the burning of liquid fuels or electricity.

→ Fires can be controlled either by cutting off the supply of air or bringing down the ignition temperature or removing the combustible substance.

→ Different types of fire extinguishers are used to control fire.

→ Combustion is of many types such as Rapid combustion, Spontaneous combustion, Explosion.

→ Flame is formed by the burning of vapours or combustible substances.

→ The Blue non-luminous zone of the flame is the hottest part of the flame.

→ A luminous zone of flame usually contains unburnt particles of carbon.

→ The calorific value of a fuel is energy produced by the complete combustion of kg of the fuel.

→ The unit of calorific value in kilojoules per Kg (KJ/Kg).

→ No fuel is an ideal fuel.

→ The burning of fuels is caused by air pollution, health hazards, global warming, acid rains, etc.

→ Global warming is a slow rise in the temperature of the environment of the earth.

→ Nitrogen and Sulphur oxides produced by the burning of fossil fuels, dissolve in water to produce acid rains.

→ Acid rain is harmful to crops, buildings, and soil.

→ CNG is a clean fuel as it causes no air pollution.

→ Combustion: It is a chemical process in which a substance reacts with oxygen to give off heat and light.

→ Combustible Substance: The substance which on burning produces light and heat, is called a combustible substance.

→ Non-Combustible Substance: The substance which cannot produce light and heat and cannot react with oxygen on burning is called a non-combustible substance.

→ Ignition Temperature: The lowest temperature at which a substance catches fire, is called its ignition temperature.

→ Inflammable Substance: The substance which has low ignition temperature and catches fire easily.

→ Fire Extinguisher: A device used to control fire.

→ Combustion: The process of burning fuel to give light and heat.

→ Calorific Value: The energy produced by the complete burning of 1 kg of fuel.

→ Global Warming: The slow rise in temperature of the environment of the earth.