Question

1 what is a physical change? give three examples
2 why is boiling a physical change and not a chemical change?
3 what is a chemical change?

Explanation:

1. A physical change is a change in the form or state of matter without altering its chemical composition. Examples include melting ice (solid - liquid change), breaking glass (change in shape), and cutting paper (change in size).
2. Boiling is a physical change because it involves a change of state from liquid to gas. The chemical composition of the substance remains the same. For example, when water boils, it changes from liquid water to water vapor, but both are still composed of H₂O molecules.
3. A chemical change is a process in which one or more substances are transformed into new substances with different chemical properties. For example, rusting of iron (iron reacts with oxygen to form iron oxide), burning of wood (wood reacts with oxygen to produce carbon - dioxide, water, etc.), and digestion of food (complex molecules are broken down into simpler ones).

Answer:

1. A physical change is a change in form or state without altering chemical composition. Examples: melting ice, breaking glass, cutting paper.
2. Boiling is a physical change as it's a state - change and the substance's chemical composition stays the same.
3. A chemical change is a process where substances are transformed into new substances with different chemical properties.