September 14th 2020
We have been investigating different forces in science this week.
We put raisins into a glass of 7-Up and into a glass of tap-water. The raisins in the 7-Up began to bob up and down from the bottom of the glass to the top and then down again. The raisins in the water just sank to the bottom and stayed there.
The 7-Up contains carbon dioxide which causes the fizziness. The raisin surface is rough and little bubbles of carbon dioxide cling to it. The force of all the little bubbles lift the raisin to the surface (like the balloons lift the house in the film Up). When the raisin reaches the surface the bubbles burst and the raisin sinks back down again.
After a while the dancing raisins became less active as the carbon dioxide leaves the 7-Up (this is what happens when soft drinks go flat).
Sorry about the sideways video - couldn't rotate it.
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