In this month's 20 Minute Lab, we're going to see what happens when we submerge gummy bears in different liquids and solutions. We chose six different liquids to try, but you don't have to stick to those - you can choose any liquids you have around your house that you want to test!
Safety Warning: Don't eat the experimental gummy bears! They will taste gross and also might have bacteria from being handled, soaked, and left out. Set aside some regular gummy bears for snacking!
LET'S GET STARTED!
WHAT'S GOING ON?
1) Why didn't the gummy bears dissolve?
The sugar in candy dissolves easily with water, because the molecules from the sugar are attracted to the molecules of the water, so the sugar breaks up to join the water particles.
In addition to sugar and water, however, gummy bears also contain gelatin. (Gelatin is what makes the bears chewy!) A gummy bear (like other gelatinous candies) has a semi-permeable membrane, meaning the outer layer is a wall-like structure with little holes in it.
When you submerge a gummy bear in water, the sugar can't get out because sugar molecules are too big to fit through the holes. The gelatin holds the general shape together. Therefore, it doesn't dissolve. To learn more about semi-permeable membranes, try our 20 Minute Lab: Naked Egg, Big Egg, Small Egg.
2) What made the gummy bears change size?
But why did your gummy bear in the plain water get huge? Well, water molecules are smaller, and they CAN move through the semi-permeable membrane to get in or out. Why would water move into the bear and not just stay where it is?
In chemistry, molecules like to move from an area of high concentration to low concentration until there is an equal amount in both areas. This principle is called osmosis.
What about the other liquids you used? Well, you can tell by the size of the resulting bear that a lot of those other solutions had water mixed with something already (baking soda, sugar in the juice, fats and proteins in the milk). Not as much water was needed to balance out both sides, therefore, those bears didn't get as big.However, there were two exceptions to just plain getting bigger:
Notice that your bear in the salt water stayed pretty much the same or may have even got smaller! That's because salt molecules are very small, and can move easily through the bear's membrane. So the salt from the glass can move into the bear until the concentration is closer to equal. If you added even more salt to the water, and the concentration would be greater outside of the bear, and water from the bear would be drawn out into the glass. In this case, the bear would shrink in size. Give it a try to see what happens!
You may have noticed that your vinegar bear grew but also started to fall apart! That's because vinegar is an acid - it slowly starts to break down the gelatin that holds the bear's shape together.
Looking for more candy-based science experiments? Check out these other experiments from our blog page:
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