Question

Decide whether each of the following is a chemical or physical change.

1. A plant uses carbon dioxide and water to make sugar.
2. rubbing alcohol evaporates when placed on the skin.
3. fireworks explodes at a holiday celebration
4. ice forms on the bridge as the temperature drops in wintry weather.

Answer 1

A plant making sugar is a chemical change, alcohol evaporating is a physical change, fireworks exploding is a chemical change, and ice forming is a physical change.

Step-by-step explanation:

Defining Physical and Chemical Changes

To determine whether a change is chemical or physical, we look at whether the molecular structure of the substances involved has changed. A physical change is a change in the state or properties of matter without any accompanying change in its chemical identity. A chemical change (or chemical reaction) occurs when the substances involved change into entirely new substances with different properties.

1. A plant using carbon dioxide and water to make sugar is a chemical change, as new substances (sugars) are produced.
2. Rubbing alcohol evaporating when placed on the skin is a physical change because it changes from liquid to gas without a change in chemical composition.
3. Fireworks exploding is a chemical change because it consists of numerous chemical reactions that emit light and sound.
4. Ice forming on a bridge as the temperature drops in wintry weather is a physical change because water changes from liquid to solid state without any change in its molecular structure.