Two scientific questions...contest (default question mark follows this text)?

Question

The first person to answer both of these questions correctly gets a best answer rating as soon as it lets me (24 hours). The answers are all I require, I don't need an explanation for why the answer is the correct answer. I know both of the answers and I will post the explanations once I chose the best answer. I'm not claiming these questions are difficult - this is just a way to kill some time :-)

1.) Why does hot air rise?
2.) How can you add or remove large amounts of heat from a substance without changing its temperature?

Good luck!

I hate how it abbreviates long words in the title. It's supposed to say "contest."

Mr. Dan in Boston wins. And thanks to explaining it anyway...it saves me the trouble!

I love simple explanations :-)

Answer 1

1) Hot air is less dense then cool air, so it "floats" up
2) You can do this if the substance is changing state, like water freezing. It will be at 32 degrees F for quite a while.

Answer 2

1. Hot air doesn't rise. Cold air is denser than hot air and will settle below warmer air, resulting in hot air being at the top.

2. You can add or remove heat energy from a substance without changing its temperature by simultaneously increasing or decreasing its volume. This is seen best with gasses - not sure if it works for solids or liquids.

Dang - too slow and didn't even think of the phase changes!

Answer 3

Hot air is less dense and experiences a buoyant force

Whenever there is a change of state, such as the solid-liquid or the liquid-gas transition, heat energy can be added without a temperature change. The change of state requires energy, so added energy goes into that instead of increasing the temperature.

Answer 4

Hot air rises because it is less dense than cold air.

A bubble of air rises in water cause it is less dense than water. Is that one of the questions?

You can remove heat from something without changing its temperature just by making it smaller.

Things that are green often contain green paint. Was that one of the questions?

Answer 5

hot air rises because it is less dense than cold air. you can add a lot of heat to a substance without changing its temperature during a phase change (melting/boiling it).

Answer 6

1. hot air rises because it molecules are moving faster (less dense)so it expands, moves, and sits on cold air (it's molecules are moving alot slower)

2.You can remove heat from something without changing its temperature just by making it smaller.

Answer 7

1. Hot air rises because it is less dense than cool air
2. To remove hot air pump in cold air systematicly.
To add hot air pump in more hot air.