Atmospheric Pressure
Properties of Matter

Heavy Atmosphere

At home for 5-11 11-14


What you need

  • A vacuum cleaner
  • A large, strong, clear plastic bag
  • Bathroom scales
  • A board about the scales’ size
  • Sticky tape

Instructions

  1. Place the board under the scales, put them together into the bag and wrap the plastic round them, fastening with sticky tape
  2. Stand the bag flat on the floor, put the vacuum pipe into the bag and hold the plastic tight round it. Switch the machine on
  3. Once the air has been sucked from the bag, the scales should read about 150kg or more; with a perfect set-up they’d record about a tonne! (You may need to try different scales or reset them for this to work)

Results and Explanation

Normally, the air above and below empty scales pushes equally in all directions, so the forces cancel out and they read zero. With a nearly airless bag, the weight of the atmosphere pushes down on the scales but little force pushes up.

These experiments have not been specifically safety tested for home use but we believe them to be safe if the instructions are followed. Adult supervision or direction is recommended as appropriate. All experiments are carried out at your own risk.

Atmospheric Pressure
is a special case of Pressure
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