Question

Why does heating an object increases its thermal energy?

Answer 1

All objects contain internal energy. Some of this is due to the movement of the particles in the object. When an object is heated, its particles move more vigorously and its internal energy increases.

Answer 2

the average kinetic energy of its particles increases. When the average kinetic energy of its particles increases, the object's thermal energy increases. Therefore, the thermal energy of an object increases as its temperature increases.