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Watch this one together

~15 min · materials: a bike pump (feel the barrel get warm as you pump), a spray can or a squirt of hand sanitizer (feel the cold as it evaporates), and permission to peek at the outdoor ac box or feel the air behind the fridge

How does the AC make cold air?

Pump a bike tire fast and feel the pump barrel — you just made the 'squeeze = hot' half of an air conditioner with your own arms. Then feel the icy puff from a spray can: that's the 'expand = cold' half.

Talk about it

  • Touch-test the warm air behind the fridge and above the outdoor AC box while the house is cooling — where is all that heat coming from?
  • Go on a heat-mover hunt: find every machine in the house that moves heat (fridge, freezer, AC, heat pump, dehumidifier).
  • On a humid day, look for the AC's drip line — why does a machine that makes cold end up making water?
Watch it together

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