5 Oct 2018

A Science Trick to Try at Home

Instructions from Margriet Ruurs

You -- yes, you, right there -- can turn two solids into one liquid. It's not magic. It's science.

How can you turn a solid substance into a liquid without adding any liquid? Here’s a fun trick to try at home. All you need is a spoonful of sugar and some fresh yeast. You can buy fresh yeast at any bakery.

Instructions:
Fresh yeast. Image by Hellahulla, from
Wikimedia Commons
  • In a small bowl put a small slice of the fresh yeast.
  • Sprinkle a spoonful of sugar on top.
  • Just let it sit for a few minutes. You’ll notice the yeast turning darker.
  • After a while, take a teaspoon and stir the two solid materials. 


You’ll find that both solid ingredients have turned into a liquid all by themselves! This process is called osmosis.

White sugar is made up of solid crystals -- until the crystals
meet the moisture in the fresh yeast.
The sugar crystals dissolve because of the humidity (dampness) in the fresh yeast, forming a highly concentrated sugar solution. But the sugar concentration inside the yeast cells is low.

The liquid containing a large amount of sugar has a natural tendency to mix with the liquid that has less sugar and even out the sugar concentration. The yeast cell membranes separating the two solutions aren't strong enough to overcome that force, so the membranes break down. Then the water inside the cells bursts out. Pretty soon, all the sugar is completely dissolved in the released water.

And presto! -- Osmosis has turned your two solids into one liquid. It's a little magical, but it's science magic!

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