Viewer Question: Why is it colder in the mountains if heat rises?

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This question came from Taylor and Emma from Ebner Elementary. They want to know why mountains are colder if hot air rises.

Air is made up of molecules. As the temperatures rise the molecules speed up and use more space. Because the molecules take up more space there are fewer molecules in a certain area which makes the air lighter. The lighter and warmer the air is the faster it will rise.

As the temperatures fall the molecules slow down. The slower the molecule is the less space it takes up. This allows more molecules to be packed tighter together. The higher amount of molecules means denser and heavier air.

Now, let’s look at why the mountains are colder. As hot air rises it expands and cools. The higher you go up the less air pressure there is allowing the air to continue to expand. The more the air molecules expand the cooler that will become. To make things simple the air roughly drops 4 degrees per 1,000 feet you go up in altitude.

Here is an example. If the surface temperature is 70 degrees the temperature at 5,000 feet would be near 50 degrees. That is because you went 5,000 feet above the surface and for every 1,000 feet it got 4 degrees cooler. If a mountain is 5,000 feet tall it would be 50 degrees at the top. 70-4-4-4-4-4=50.

The mountains are cooler because there is less air pressure than at the surface. The further away you are from the surface the less the pressure gets and the colder the air is. That is why the top of the mountain is colder than the base of the mountain.

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