Give two examples for each of the following cases:(a) Physical changes which are reversible. [1 mark](b) Physical changes which are not reversible. [1 mark](c) Chemical changes. [1 mark]

(a) Physical changes which are reversible:

1. Melting of ice: Ice can be melted to form water, and this process can be reversed by freezing the water to form ice again.
2. Folding a paper: When you fold a paper, its shape changes. But you can reverse this process by unfolding the paper to get back its original shape.

(b) Physical changes which are not reversible:

1. Breaking a glass: When a glass is broken, it cannot be put back together to form the original glass.
2. Cutting a tree: Once a tree is cut down, it cannot be put back together to form the original tree.

(c) Chemical changes:

1. Burning of wood: When wood is burned, it turns into ash, carbon dioxide, and water vapor. This is a chemical change because new substances are formed and the process cannot be reversed.
2. Rusting of iron: When iron is exposed to moist air, it reacts with oxygen to form iron oxide or rust. This is a chemical change because a new substance is formed and the process cannot be reversed.