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Matter –> Anything that occupies space (or has volume) and has mass is called matter.
Matter around us exists in three form 1. Solid, 2. Liquid and 3. Gas.
Everything around us is made up of matter.
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Volume –> The space taken up by a liquid is called its volume. The amount of a liquid is measure the unit litre (I or L).
Length is measured in metre (m)
Weight is measured in gram (g)
Liquid is measured in litre (I or L)
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Q. Is water matter?
Ans. Yes, water is matter. It occupies space and also has mass.
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Q. Classify the following substances as solids, liquids and gases.
Chair, cold drink, eraser, oxygen, water vapour, milk, pencil, duster, nitrogen, orange juice, apple juice, apple, carbon dioxide, almirah, ice-cube, water
Ans.
Solid –> Chair, eraser, pencil, duster, apple, almirah, ice-cube.
Liquid –> cold drink, water, milk, orange juice, apple juice, apple.
Gas –> oxygen, water vapour, nitrogen, carbon dioxide.
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Q. Name a substance or matter whitch found in all three states around us.
Ans. Water is a substance or matter whitch found in all three states around us.
1. Solid - Ice cube
2. Liquid - water and
3. Gas - water vapour
Atoms –> Matter is made up of tiny particles called atoms. Atoms are the building blocks of matter.
They are very tiny and cannot be seen with the naked eye.
Molecules –> Atoms join together to form molecules.
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Intermolecular Force –> The force between two atoms or molecules is known as in Ram molecular force.
Intermolecular Spaces –> The space between two atoms or molecules is known as in Ram molecular space.
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SOLIDS
1. Solids have a definite shape and volume.
2. Molecules in a solid are very tightly packed.
3. Solids cannot flow.
4. Intermolecular force of attraction is very strong.
5. Intermolecular spaces are almost negligible.
LIQUIDS
1. Liquids have no definite shape but have a definite volume.
2. Molecules in a liquid are loosely packed.
3. Liquids can flow.
4. Intermolecular force of attraction is weak as compared to solids.
5. Intermolecular spaces are more as compared to solids.
GASES
1. Gases neither have a definite shape nor a definite volume.
2. Molecules in a gas are very loosely packed.
3. Gases flow in all directions.
4. Intermolecular force of attraction is the weakest.
5. Intermolecular spaces are very large.
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Matter can be classified as pure substances and impure substance. Elements and compounds are pure substances, whereas mixtures are not pure
PURE SUBSTANCES
Element: A pure substance that is made up of only one kind of atoms is called an element. Elements are made up of identical atoms.
As Copper, iron, silver, gold, helium, hydrogen and mercury are made up of one kind of atoms. There are more than 115 elements known.
Elements can combine together in different ways to form millions of compounds.
Copper is an example of an element. It is made up of only copper atoms.
Compound: A substance that contains atoms of two or more elements is called compound.
Thus a compound is formed when two or more elements combine in a fixed ratio by mass.
For example, water that we drink is a compound. It is made up of two elements hydrogen and oxygen in the ratio of 2:1.
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IMPURE SUBSTANCES
Mixture: When two or more substances are put together and they do not combine, then a mixture is formed.
For example, if we add sugar to water, we get mixture of sugar and water.
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Checkpoint 1
Fill in the blanks:
1. Anything that occupies .......... and has .......... is called matter.
2. Matter exists as .......... , .......... and .......... .
3. A cup is a ........ whereas milk is ....... matter.
4. Atoms combine to form a ..........
5. Molecules in a liqui are .......... packed as compared to solids.
6. Hydrogen is an ........... whereas water is a
..............
7. Air is a ......... of gases.
Ans. 1. Space, mass, 2. Solid, liquid, gas, 3. Solid, liquid, 4. molecule, 5. Loosely , 6. elements, compound, 7. mixture
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CHANGES IN THE STATE OF MATTER
Matter can change its state either by heating or cooling.
Melting –> The process of changing of a solid into liquid on heating is called melting.
Freezing –> The process of changing of a liquid into solid on cooling is called Freezing.
Evaporation –> The process of changing of a liquid into its gaseous form on heating is called evaporation.
Condensation –> The process of changing of gas into liquid on cooling is called condensation.
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SOLUTIONS
Soluble Substances –> The substances which dissolve in water are called soluble substances.
Sugar and common salt, dissolve completely in water so they are soluble materials.
Insoluble Substances –> The substances which do not dissolve in water are called insoluble substances.
Chalk powder and sand do not dissolve in water so these are insoluble in water.
Solubility –> The property of dissolving of a substance in water is called solubility.
Miscible Liquids –> Those liquids that dissolve with each other are called miscible liquids.
Liquids like vinegar, milk and lemon juice dissolve in water are miscible liquids.
Immiscible Liquids –> Liquids that do not mix with each other are called immiscible liquids. Oil and water are immiscible liquids.
Do all liquids mix with each other?
No! There are liquids that do not mix with each other.
Take some mustard oil in a beaker. Now, add some water to it. Stir the mixture well and allow it to stand for some time. What do you observe?
You will see that mustard oil and water do not mix with each other and forma separate layers. Mustard oil forms the upper layer, whereas water forms the lower layer.
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Q. Can gases dissolve in water?
Ans. Some gases can dissolve in water, whereas others do not.
Nitrogen gas does not dissolve in water and is said to be insoluble in water.
Oxygen and Carbon dioxide gas dissolve in water and is said to be soluble in water.
★ Oxygen gas can dissolve in water. Aquatic animals and plants use the oxygen gas dissolved in water to survive.
★ Carbon dioxide gas can also dissolve in water. Aquatic plants use carbon dioxide gas dissolved in water for photosynthesis.
Q. Which gas is dissolved in soft drinks to make them fizzy?
Ans. Carbon dioxide
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PHYSICAL AND CHEMICAL CHANGES
Change –> Changing of a substance into its shape, size, stages, temperature etc is called change.
There two type of the cha 1. Physical change and 2. chemical change.
Many changes take place around us. Some of them are as follows:
> Growing of a baby into an adult
> Melting of butter
- Melting of wax
- Burning of paper
- Growing of a seed into a sapling
- Rusting of an iron nail
List some more changes that you observe taking place around you.
You will observe
> The wooden stick becomes smaller in size, but is still wood.
> The paper becomes smaller in size, but is still paper.
> On inflating, the shape and size of the balloon change, but it is still a balloon.
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Physical Changes –> Such types of changes in which a substance undergoes a change in size, shape or physical state but no new substance is formed are called physical changes.
In these changes, the substances do not change. They remain the same.
★ Like ice (a solid) into water (a liquid) by heating
★ and by further heating it we can change water into vapour (a gas).
★ Water vapour (gas) can be changed into liquid by cooling.
★ Liquid matter can be changed back into ice (solid) by freezing.
A change in which no new substance is formed is called a physical change.
Physical change shows the following characteristics:
★ The size, shape or physical state of a substance may change.
★ Most physical changes are temporary.
★ Most physical changes are reversible.
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Chemical Changes
Such types of a change in which new substance (or substances) is produced and it's chemical property changes is called a chemical change.
Most chemical changes are permanent and irreversible. New substance (or substances) is formed in a chemical change.
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Q. When a paper is burnt, we get ash. Can we get the paper back from the ash?
Ans. This is not possible because a chemical change took place here. When substances burn, they combine with oxygen and new substances are produced.
A chemical change shows the following characteristics:
★ It is a permanent and irreversible change.
★ It is a change where a new substance is formed.
★ It is a change where the properties and composition of the new substance formed are different from the original one.
When an incense stick burns, carbon dioxide, water vapour and ash are produced.
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Q. Is making of curd from milk a chemical change?
Ans. Yes, Curd is different from milk. We cannot get back milk from curd. It is a permanent and irreversible change.
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Name the process.
Checkpoint 2
1. Change of state from solid to liquid
2. Changing a liquid into a solid
3. A temporary change
4. The property of dissolving of a substance in water
Ans. 1. Melting, 2. Freezing, 3. Physical change 4. Solubility
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SCIENCE VOCABULARY
Matter –> Anything that occupies space and has mass is called matter
Atom –> tiny particle that forms building blocks of matter
Molecule –> tiny particle formed when two or more atoms combine
Element –> a substance that consists of atoms of only one kind
Compound –> a substance that contains atoms of two or more elements
Physical change –> a change that does not produce a new substance
Chemical change –> a change that produces new substances
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Wrapping it up
★ Anything that occupies space and has mass is called matter
★ Matter is made up of atoms and molecules.
★ Atoms are very tiny particles that cannot be seen with the naked eye.
★ Atoms join to form molecules.
★ Matter is classified as pure and impure substances.
★ Elements and compounds are pure substances.
★ Mixtures are impure substances.
★ Elements are made of identical atoms, whereas compounds are made up of two or more elements.
★ Matter can change from one state to another by heating or cooling.
★ Materials which can dissolve in water are called soluble materials while those cannot are called insoluble materials.
★ Most physical changes are temporary and reversible. No new substance is formed in a physical change.
★ Most chemical changes are permanent and irreversible. New substance (or substances) is formed in a chemical change.
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EXERCISES
A. Fill in the blanks.
1. Everything in nature is made up of ...........
2. ........... have a definite shape and volume.
3. ........... flow in all directions.
4. Oil and water are ........... liquids.
5. A new substance is formed in a ......... change.
Ans. 1. matter., 2. Solids, 3. Gases 4. immiscible 5. chemical .
B. Write True or False.
1. Molecules of gases are loosely arranged.
2. There are only 105 elements known in nature.
3. Gases cannot dissolve in water.
4. Physical changes are permanent changes.
5. Making of curd from milk is a chemical change.
Ans. 1. True 2. False 3. False 4. False 5. True
C. Tick (✔) the correct answer.
1. Which of these are pure substances?
(a) element
(b) compound
(c) mixture
(d) both (a) and (b)
2. Copper is
(a) an element
(b) a compound
(c) a mixture
(d) none of these
3. Water is
(a) an element
(b) a compound
(c) an atom
(d) none of these
4. The process of changing of a liquid into a solid is called
(a) melting
(b) freezing
(c) evaporation
(d) condensation
5. A mixture of lemon juice mixed in water is an example of
(a) miscible liquids
(b) immiscible liquids
(c) chemical change
(d) None of these
Ans. 1. (a) element, 2. (a) an element, 3.
(b) a compound, 4. (b) freezing 5. (a) miscible liquids
D. Classify the following into elements, compounds and mixtures.
SALT, IRON, SUGAR, WATER, AIR, SOIL, CARBON, GOLD, BAKING SODA, SODA WATER, HYDROGEN, SEA WATER
Elements Compounds Mixtures
Ans.
Elements–> Iron, Carbon, Gold, Hydrogen
Compounds –> water, sugar, salt, Baking soda
Mixtures –> Air, soil, soda water, seawater
E. State whether each of the following is a chemical change or a physical change.
1. Boiling of water
2. Melting of ice cream
3. Lighting of a matchstick
4. Burning of gas in a stove
5. Rusting of a nail
6. Tearing of clothes
Ans.
Chemical Change –>
3. Lighting of a matchstick
4. Burning of gas in a stove
5. Rusting of a nail
Physical Change –>
1. Boiling of water
2. Melting of ice cream
6. Tearing of clothes
F. Answer the following questions.
1. What do you understand by matter? Write its different forms.
Ans. Anything that occupies space (or has volume) and has mass is called matter.
Matter around us exists in three form 1. Solid, 2. Liquid and 3. Gas.
2. Explain any three characteristics of solids.
Ans.
SOLIDS
1. Solids have a definite shape and volume.
2. Molecules in a solid are very tightly packed.
3. Solids cannot flow.
4. Intermolecular force of attraction is very strong.
5. Intermolecular spaces are almost negligible.
3. Explain any three characteristics of liquids.
Ans.
LIQUIDS
1. Liquids have no definite shape but have a definite volume.
2. Molecules in a liquid are loosely packed.
3. Liquids can flow.
4. Intermolecular force of attraction is weak as compared to solids.
5. Intermolecular spaces are more as compared to solids.
4. Explain any three characteristics of gases.
Ans.
GASES
1. Gases neither have a definite shape nor a definite volume.
2. Molecules in a gas are very loosely packed.
3. Gases flow in all directions.
4. Intermolecular force of attraction is the weakest.
5. Intermolecular spaces are very large.
3. Explain any three characteristics of liquids.
5. Give any four examples of the most abundant elements in the earth's crust.
Ans.
Oxygen, silicon, aluminium and iron are four examples of the most abundant elements in the earth's crust
6. Name two gases that are soluble in water. How are they useful?
Ans. Oxygen and carbon dioxide
7. Give two examples of
(a) Miscible liquids
(b) Immiscible liquids
Ans.
(a) Miscible liquids –> vinegar, milk and lemon juice
(b) Immiscible liquids –> Oil and water, petrol and water
8. Explain the two types of changes with examples.
Ans.
Change –> Changing of a substance into its shape, size, stages, temperature etc is called change.
Physical Changes –> Such types of changes in which a substance undergoes a change in size, shape or physical state but no new substance is formed are called physical changes.
In these changes, the substances do not change. They remain the same.
Physical Change –>
1. Boiling of water
2. Melting of ice cream
3. Tearing of clothes
Chemical Changes
Such types of a change in which new substance (or substances) is produced and it's chemical property changes is called a chemical change.
Most chemical changes are permanent and irreversible. New substance (or substances) is formed in a chemical change.
Chemical Change –>
1. Lighting of a matchstick
2. Burning of gas in a stove
3. Rusting of a nail
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