Bob has a cup of hot chili. It is too hot to eat.

After ten minutes, the chili is cool enough for him to eat.
What has happened to the chili's thermal energy?

A.
It has increased the air's potential energy.
B.
It has increased the chili's kinetic energy.
C.
It has increased the air's thermal energy.
D.
It has increased the chili's potential energy.

The answer is It has increased the air's thermal energy. Which is C.

Explanation:

Over time, thermal energy tends to spread out through a material and from one material to another. As a result, a hot material tends to cool down over time.

Since the chili is in contact with the air, some of its thermal energy transferred to the surrounding air, thereby increasing the air's thermal energy.