Science At Home - Cartesian Diver

Are you controlling the ketchup packet with magic? Or is it science?

This demonstration has nothing to do with magical powers - it’s 100% science! We’re using water and the ketchup packet to demonstrate buoyancy and density.

Inside the ketchup packet is an air bubble. When the ketchup package is floating, it’s density is less than the density of the water. When you squeeze the bottle, you are also compressing the air bubble inside the packet. This increases the density of the ketchup packet and causes it to sinks to the bottom!

The classic Cartesian Diver demonstration use a glass eye dropper and was named after Rene Descartes, a French scientist and mathematician.

If the packet doesn’t float, you can change the density of the WATER by adding salt!

Continue exploring density! We’ve done other demonstrations that explore the density of water - check out those video here:

Salt Water Density: https://www.sasksciencecentre.com/real-science-real-fun/science-at-home-salt-water-density

Self-Crushing Can: https://www.sasksciencecentre.com/real-science-real-fun/self-crushing-can

Water Lifting Candle: https://www.sasksciencecentre.com/real-science-real-fun/2020/4/06/science-at-home-water-lifting-candle


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