How does the air on a hot day compare with the air on a cold day? Answers:

A. On a hot day, air molecules have more energy
B. On a cold day, air molecules move faster
C. On a hot day, the air contains more nitrogen
D. On a cold day, air molecules don't move at all

Which one is it?

A. On a hot day, air molecules have more energy

Explanation:

The molecules in air are affected by temperature. The air molecules are always moving; however, their movement depends upon the hotness and coldness of the environment. When the day is hot, the temperature is high and this allows the molecules to increase their kinetic energy. This makes choice A correct.

On the contrary, when the day is cold, the temperature decreases and this prevents the molecules from moving so much. This means their kinetic energy decreases. This makes choice B incorrect.

Nitrogen is always abundant on the Earth's atmosphere, so this makes choice C incorrect. Take note that molecules are constantly moving, thus choice D is incorrect.