Question

1. when a substance melts or boils, is it a physical or chemical change? explain your choice.

Explanation:

A physical change involves a change in the physical state (solid, liquid, gas) of a substance without altering its chemical composition. When a substance melts (solid - liquid) or boils (liquid - gas), only the intermolecular forces are overcome, and the chemical identity of the substance remains the same. For example, when ice melts into water, both ice and water are composed of $H_2O$ molecules.

Answer:

It is a physical change.