why does heat rise?

Answer 1

It weighs less.
The more active (and charged) molecules spread further apart

Answer 2

Actually, heat doesn't rise. The only time heat moves is to leave something hot and enter something cooler. What does rise is hot air. I know that may sound like a meaningless distinction, but its importand in the explanation of why it rises.

When a gas gets hot, it becomes more energetic. (Heat is just a form of energy.) The gas molecules start moving around faster, and bumping into each other harder and more often. This creates air pressure, which the gas relieves by expanding. All substances do this to some degree. But gases do it much more than solids or liquids because their molecules aren't bound together.

When the air expands, you have the same mass of air in a larger volume. This means it's less dense. Anything less dense than cool air will float in it. This includes hot air. So the hot air rises through the cold air, taking the heat with it.

Answer 3

Why have so many people given a negative rating to Dickie's answer: 'does it? how about ice on a pond'.

This is a very valid point and an excellent example of why the distinction between 'heat' and 'hot air' should be made!

Incidentally, ice floats because its crystal structure takes more room (is less dense) than the water. This is due to the water's hydrogen bonds which hold each water molecule together. Here's your homework: research different ice structures and find how many different phases there are.

Answer 4

Heat is energy. When we say something is hot, we really are saying it has a lot of stored energy.

What does this energy do?

Matter is made up of incredibly small pieces called atoms and molecules. Atoms and molecules are always moving.

The more energy these atoms and molecules have, the faster they move. The faster they mover, the more space they take up.

If something is hot, it weighs the same as if it were cold, but it just takes up more space.

This leads us to the concept of density. Because hat air takes up more space than cold air, hot aur has a smaller density.

Less dense hot air will "float" above the more dense cold air.

Answer 5

Heat doesn't rise.
Some hot materials such as gases and liquids tend to rise as they are less dense than their surrounding cooler gas or liquid. Some liquids, including water between 0C and 4C, actually get more dense with temperate and so would fall in a surrounding cooler body of water.

The answer you are really looking for is that in general hotter gases and liquids are less dense than a cooler version of the same gas or liquid.

Answer 6

Probably because heat is energy. Thermal energy from the sun does not heat the air though which it is passing. Heat tends to flow from the hot to the cold site. Because of decreasing temperature with altitude, heat rises, following it 's general flow pattern.

Answer 7

Heat does not rise, it radiates.
But if you are referring to why warm air rises.
energy or ( heat ) is absorbed by the molecules in the air.
they become more active, and become more active, bumping into their neighbor creating more space between the molecules.
Since there is more space between the molecules, the density drops.
Now the more dense molecules or less active molecules are closer together making them more dense. since they are more dense they are heavier.

It's not that warm air rises, but the more dense air is heavier and displaces the less dense air up.

Like wood in water. Wood is less dense and rises, while water is more dense. while a stone is more dense and will sink in water.
same principle with warm or cool air.

Answer 8

Heat only "rises" in the presense of gravity. That is because hot air is less dense than cold air.

Answer 9

Convection

Answer 10

Cold air molecules are closer together making it more dense than warm air. Warm air is lighter, than cold.

Answer 11

Lighter than air. Or is it just to keep up with the cost of it now days!!