Science Corner: Why warm air rises

Science Corner

MOBILE, Ala. (WKRG) — Science Corner with Meteorologist Caroline Carithers talking about (and showing) why warm air rises!

Needed Supplies: Warm water, red food coloring, cold water, blue food coloring, 2 clear cups, clear straw

Steps (check out the video for a visual!):

  1. Heat 1 cup of water in microwave for 1 minute, add red food coloring
  2. Fill other cup with cold water, add blue food coloring
  3. Take clear straw and put in red (warm) water cup. Put finger on end of straw that is not in the cup to create a vacuum (top) and pull straw out of red cup with finger still covering top hole of straw. You will see red water in straw
  4. Transfer straw (with finger still on top of straw and red water still in straw) to blue (cold) cup
  5. Take finger off top of straw and put it back on with straw still in blue (cold) cup.
  6. Take out straw with finger still on top of straw and observe!

Explanation: After you have followed the steps (check out video if it is confusing!), you will notice the red and the blue water is separate with the blue water on the bottom. Why is this? The cold blue water represents cold air while the warm red water represents warm air. You may have heard warm air rises, but why? Warm air is less dense than cold air. Density is technically mass per volume, but in very simple terms, the cold air’s molecules are more compact. This causes it to sink. Warm air’s molecules are less compact causing it to rise.

For example, a styrofoam cup is less dense than a ceramic cup, so the styrofoam cups floats while the ceramic cup sinks. Same goes for wood and a rock of the same size. Wood is less dense than a rock, so the wood floats and the rock sinks!

Check out the video for the experiment!


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