Properties of Matter

Jam Jar Sessions

Enrichment Activity for 5-11 11-14

What you need

  • Three identical jam jars
  • Jam
  • Water
  • A gentle slope


  1. Fill one jar with jam, another with water and leave the third empty
  2. Race all three jars down the slope and see which wins. Try racing them in pairs – the water-filled jar versus the jam-filled jar etc
  3. The water-filled jar should be fastest by a slight amount, the jam-filled jar next, and the empty jar slowest

Results and Explanation

The force due to the weight of the jars makes them rotate as well as move down the slope. The empty jar’s mass is around its edge, so a lot of the force goes into making this mass rotate.
More of the jam-filled jar’s mass is near its centre so less of the force goes into making this mass rotate. The water in the third jar doesn’t rotate, so all of the force goes into moving the water straight down the slope.

IOP DOMAINS Physics CPD programme

Electricity CPD videos

Our new set of videos gives teachers and coaches of physics a preview of the training we offer ahead of this term's live support sessions.

Find out more