Why does hot air rise?

yes you are right. it rises because it is lighter.

why is it lighter? well in hot air obviously the molecules are at a high temperature and so they are moving here and there really fast. sooo the air is expanded.

for example lets say that when the air was not hot there were 500 air molecules in 1 square meter. when these particles are heated up they move here and there and so if we check the exact same area we measured before (1 square meter) at one any one time, we can see that there are lesser number of air molecules there, hence they rise as there is less mass in that volume when compared to the surrounding.

why it gets colder? well when it goes higher up the pressure exerted by the surrounding atmosphere on this hot air decreases. and according to Gay lussac's lay pressure is directly proportional to temperature and so when pressure decreases the temperature also decreases, so higher up in the atmosphere it is cold.

Hot air rises due to the way molecules behave at different temperatures. Air, which consists of various gases, can easily have its ambient temperature change.

When air is heated the molecules in the air move around more and thus take up a larger area reducing its density. When it gets colder the molecules move less taking up less space and therefore becoming denser.

An interesting fact is that ALL elements' molecules stop moving, even nitrogen, at -275 degrees Celsius. This temperature is also known as 0 degrees Kelvin.

it rises because when it is hot, it vibrates. then, it pushes other molecules away because the molecules are vibrating. this makes it less dense, and lighter. since it is lighter, it rises.

it is cold high in the atmosphere because on the ground, there is the ground to absorb heat and give it to the air. The main reason is that the air is less dense, so there is less pressure. when there is less pressure, it is colder.

you answered your own question yourself, the atmosphere keep the temperature, or try, at the same level anywhere, but has the sun rays are on the ground, the hot air is on the ground, so the atmosphere try to make it equal, and bring it back up...

Because when you think your someone special to the human race and you fart -It rises and smells just like everyone else's dork wad

google search mpre info hope this helps