Dancing Sultanas
July 26, 2017
Watch your favourite school snack dance in soda water!
Suitable for kids aged 5+
You Need:
- 10 x Sultanas
- 1 x Litre of Soda Water
- 1 x Transparent Contrainer
What to do:
- Pour the soda water into the container.
- Gently add the sultanas one at a time to the soda water.
- Watch them float to the surface and then sink down to the bottom.
- How long will this dancing go on, and why?
Why is it so?
How are they dancing? Well soda water contains a large amount of dissolved carbon dioxide. That's the stuff that makes it fizzy and fun to drink! The bubbles are less dense that soda water, so they rise to the surface. The sultanas initially sink to the bottom as they are heavier than water, but as the bubbles start to rise to the surface, they wedge themselves into the crevices of the sultanas, providing a buoyant force to help threm rise to the surface!
But they won't float on the surface for ever! Once the sultanas reach the surface, the bubbles supporting them pop! Causing them to sink again. But they will rise again as new bubbles lift them up! Will this rising and sinking motion go on forever?
No it won't. The rising and sinking motion will stop once all the carbon dioxide has escaped (soda goes flat). You will also notice that with time the dried sultanas will have absorbed some water and become too heavy to rise. You will also notice that the sultana will expand and cause its skin to become smooth, leaving no crevices for the bubbles to wedge between.
Instead of using soda water you could create a bubbly liquid by mixing vinegar and baking soda, or experiment with other objects that can dance too!
But they won't float on the surface for ever! Once the sultanas reach the surface, the bubbles supporting them pop! Causing them to sink again. But they will rise again as new bubbles lift them up! Will this rising and sinking motion go on forever?
No it won't. The rising and sinking motion will stop once all the carbon dioxide has escaped (soda goes flat). You will also notice that with time the dried sultanas will have absorbed some water and become too heavy to rise. You will also notice that the sultana will expand and cause its skin to become smooth, leaving no crevices for the bubbles to wedge between.
Instead of using soda water you could create a bubbly liquid by mixing vinegar and baking soda, or experiment with other objects that can dance too!
Do more cool experiments with the science kits available on this website.
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