Question

When a substance is heated, what causes its properties to change?

Answer 1

The molecules vibrate when the substance is heated, and the shape of the substance begins to form a different shape. For example: when you hear up metal it will melt becuase its molecules are changing and moving.

Answer 2

Molecule movement. Ice is so hard because molecules are not moving, and the space between them are small. Hot water has bigger space between molecules that are always in motion.