Answer:
air warms up, the molecules start to vibrate and bump into each other, increasing the space around each molecule. Because each molecule uses more space for motion, the air expands and becomes less dense (lighter). ... The opposite effect happens when air cools.
Step-by-step explanation:
temperature of the air drops off very rapidly at first, but with every drop in temperature, it gives off less energy during the next interval of time, so the rate of cooling decreases. In contrast, the water cools very, very slowly; the energy it emits is a drop in the bucket (so to speak) compared to the total amount of energy in the whole cubic meter, so the temperature change is small.