Upthrust
Properties of Matter

Lava Lamp

Enrichment Activity for 5-11 11-14


What you need

  • A large glass
  • Lemonade (or fizzy water)
  • Peanuts (or raisins)

Instructions

  1. Fill the glass with lemonade
  2. Stir for 1 min or leave to go slightly flat
  3. Drop some peanuts into the glass

Results and Explanation

The nuts float up to the top and fall back down again, like in a lava lamp. Gas bubbles grow on the peanuts, making them float upwards. When they reach the top the bubbles burst and the peanuts fall back down again.

Upthrust
is a special case of Force
appears in the relation Upthrust = Weight of Displaced Liquid
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