Question

fireworks explode. * 1 point
this is a physical change
this is a chemical change
salt dissolves in water. * 1 point
this is a physical change
this is a chemical change
hydrochloric acid reacts with magnesium to produce hydrogen gas. * 1 point
this is a physical change
this is a chemical change

Explanation:

1. Fireworks exploding involves the combustion of chemical compounds in the fireworks, which results in the formation of new substances like gases, light, and heat. This is a chemical change.
2. When salt dissolves in water, the salt (sodium - chloride) dissociates into its ions in the water, but no new chemical substances are formed. It is a physical change as the salt can be recovered by evaporating the water.
3. The reaction between hydrochloric acid and magnesium to produce hydrogen gas is a chemical change because new substances (magnesium chloride and hydrogen gas) are formed through a chemical reaction.

Answer:

1. This is a CHEMICAL change
2. This is a PHYSICAL change
3. This is a CHEMICAL change