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1. Fill in the blanks:
a. Burning of a fire cracker is a ______ Change.
b. The state of matter can be interchanged by _____ and ______.
c. _______ and _____ are gases that dissolve in water.
d. Dissolving a material in a liquid often _____ no increase in volume.
e. Solutions are of _____ strength throughout.
f. Intermolecular space is maximum in ______.
g. The process of ice changing in water on heating is called _________.
a. Chemical
b. Cooling,heating
c. Oxygen, carbon dioxide
d. Produces
e. Uniform
f. Gases
g. Melting
2. Write True or False.
a. In solids molecules are closely packed.
b. Liquid does not have a definite volume.
c. Sand is soluble in water.
d. Burning of paper is an example of a chemical change.
e. Solutions are of uniform strength throughout.
f. A physical change is irreversible.
a. True
b. False
c. False
d. True
e. True
f. False
3. Match the following
| 1. Soda water has | a. it becomes a liquid. |
| 2. When wax is heated | b. they break up into tiny particles. |
| 3. When solids are dissolved in water | c. carbon dioxide dissolved in it. |
| 4. Fish breath oxygen | d. produce important changes in materials. |
| 5. Heating and cooling | e. dissolved in water |
Ans.
| 1. Soda water has | c. carbon dioxide dissolved in it. |
| 2. When wax is heated | a. it becomes a liquid. |
| 3. When solids are dissolved in water | b. they break up into tiny particles. |
| 4. Fish breath oxygen | e. dissolved in water |
| 5. Heating and cooling | d. produce important changes in material |
4. Name the three states of matter.
Matter exists in three states - solids, liquids and gases.
5. Distinguish between the three states of matter.
| S. No. | Features | Solids | Liquids | Gases |
| 1. | Arrangements of molecules | very closely packed | less closely packed | loosely packed |
| 2. | Shape | has a definite shape |
do not have a definite shape, they take the shape of the container |
do not have a definite shape |
| 3. | Volume | has a definite volume | also have a definite volume | do not have a definite volume |
| 4. | Intermolecular | very strong | lesser than solids | very weak |
6. Why water is called a universal solvent?
Water can dissolve many things in it and is hence called a universal solvent. Solids like sugar and salt dissolve in water. Liquids like ink, glycerin, lime juice dissolve in water. Gases like oxygen and carbon dioxide dissolve in water.
7. Explain how water can change its form when it exists in the three states of matter.
Let us take the example of ice. Ice is the solid state of water. When ice is kept in the open, it gets heated and turns into liquid. The process of ice changing into water on heating is known as melting.
When liquid water is heated, it changes into steam or water vapour. Water vapour is the gaseous state of water. The process of a liquid changing into its gaseous state on heating is called evaporation.
When steam is cooled, it changes again to droplets of water. The change of a gas into its liquid state on cooling is called condensation.
If we keep this water in a freezer, it cools down sufficiently and changes into ice. The process of a liquid changing into its solid on cooling state is known as freezing.
8. Why does water flow but ice does not?
Ice is a solid and water is a liquid. Liquids flow but solids do not flow.
9. What is a solute? Name some solutes.
The solid that dissolves in a liquid is called the solute.
Example. Salt, Sugar
10. What is a solvent? Name some solvents.
The liquid in which a substance dissolves is called the solvent.
Example. Water, alcohol.
11. Why does the volume of water not increase when sugar is added to it?
The water molecules have spaces between them and the sugar molecules occupy these spaces. Hence, there is no increase in water level and so no increase in volume is observed.
12. Distinguish between physical and chemical change.
| Physical change | Chemical change |
| 1. No new substance is formed. | 1. New substance is formed. |
| 2. The change is reversible | 2. The change is irreversible. |
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3. Melting of wax is an example of physical change. |
3. Burning of paper into ashes is an example of chemical change |
13. When you burn an incense stick, its smell spreads out very quickly in your house. Why?
All matters are made up of tiny particles called molecules are currently moving. So they carry the smell of intense stick and spreads through the house.
14. Mrs. Sharma kept an orange bar on the table in a bowl. After half an hour it turned into liquid. She placed the bowl in the freezer. It became a solid again. What kind of change is this?
i. Orange bar to Liquid.
This conversion is called Melting.
ii. Liquid to Solid.
This Conversion is called Freezing.
15. Rahul says- Air is matter. Is he correct in saying so? Give reasons.
Air is a matter because it occupies space and has mass. Blowing of a balloon proves that it occupies space. To prove air has mass; 2 balloons filled with air is taken. Both are hanged in a scale supported by a beam. Make a hole in the white balloon and wait until it becomes empty.
