III. Descriptive Type Questions A. Short Answer Questions
1. What is matter made up of?
➤ Matter is made up of tiny particles called atoms and molecules.
2. Define melting.
➤ Melting is the process by which a solid changes into a liquid on heating.
3. Define condensation.
➤ Condensation is the process by which a gas changes into a liquid on cooling.
4. Define physical change with an example.
➤ A physical change is a change in which the form of matter is changed but not its chemical identity.Example: Melting of ice.
5. Define chemical change with an example.
➤ A chemical change is a change in which a new substance is formed. Example: Burning of wood.
6. Define solidification.
➤ Solidification is the process by which a liquid changes into a solid on cooling.
7. What is expansion?
➤ Expansion is the increase in the size or volume of a substance when heated.
B. Long Answer Questions
1. How are particles arranged in solids?
➤ In solids, particles are tightly packed in a fixed, regular pattern with very little interparticle space. They can only vibrate in place.
2. How are particles arranged in liquids?
➤ In liquids, particles are closely packed but not in a fixed position. They can slide over one another, allowing liquids to flow.
3. How are particles arranged in gases?
➤ In gases, particles are very loosely packed and move freely in all directions. They have a lot of interparticle space.
4. Explain how matter contracts.
➤ Matter contracts when it is cooled. The particles come closer together, reducing the size or volume of the substance.
5. Using appropriate examples, distinguish between physical and chemical changes.
| Physical Change | Chemical Change |
| ————————— | ————————– |
| No new substance is formed. | A new substance is formed. |
| Reversible in nature. | Usually irreversible. |
| Example: Melting of ice. | Example: Rusting of iron. |
