D.  Answer the following questions.

1. Define matter. Name the three states in which matter exists.

Answer. Matter is anything that has mass and takes up space. The three states in which matter exists are solid, liquid, and gas.

2. With the help of a diagram, show how the arrangement of particles gives a solid a fixed shape.

  Answer. Diagram:

   [ O O O ]

   [ O O O ]

   [ O O O ]

In solids, particles are closely packed in a fixed, orderly arrangement, which gives solids a definite shape.

3. What causes liquid to flow?

Answer. Liquids flow because their particles are loosely packed and can move past each other, allowing the liquid to take the shape of its container.

4. How are particles arranged in gases?

Answer. In gases, particles are widely spaced and move freely in all directions, resulting in no fixed shape or volume.

5. Explain boiling and condensation with the help of particle movement.

Answer. Boiling occurs when particles gain enough energy to move from liquid to gas. Condensation happens when gas particles lose energy and move closer to form a liquid.

6. Explain how substances expand on heating.

Answer. On heating, particles gain energy and vibrate more vigorously, causing them to move apart, which results in the expansion of the substance.

7. Why do substances contract on cooling?

Answer. On cooling, particles lose energy and move closer together, reducing the space between them, which causes the substance to contract.