Question

1. a cars paint starts to rust when it is exposed to moist air. is this a physical or chemical change? why?

Explanation:

A chemical change occurs when new substances are formed. Rusting is an oxidation - reaction. When a car's paint rusts due to exposure to moist air, iron in the metal (under the paint) reacts with oxygen and water to form iron oxide (rust), a new substance. In a physical change, the substance's chemical composition remains the same. Here, the chemical composition of the metal changes.

Answer:

It is a chemical change because rust (iron oxide) is a new substance formed through a chemical reaction between iron in the car's metal, oxygen, and water in moist air.