Answer:
1. When a substance is heated, the particles gain energy and move apart increasing the volume. This phenomenon is called thermal expansion.
2. When temperature increases, average kinetic energy increases.
Explanation:
Thermal expansion - the tendency of matter to change in volume in response to a change in temperature.
When the temperature of an object increases, the average kinetic energy of its particles increases while, when the average kinetic energy of its particles increases, the object's thermal energy increases.
The thermal energy of an object therefore increases as its temperature increases.
