Candy Chemistry Experiments
We were always told not to play with our food. How's a kid supposed to wonder and discover if they can't play?
We didn't want to waste any spinach or asparagus, so we opened up the candy cupboard for a little kitchen science and lessons in solubility, buoyancy, and reactions. What happens when you put candy in a liquid? Will it float, sink, melt or explode?
- Geyser Mentos Tube
- Demo Tank or bowl
- Candy bars (we used Three Musketeers, Kit Kat and Hershey's Chocolate)
- Gummy bears
- Mentos mint candy
- Soda (we used Sprite, root beer, Diet Coke, Diet Pepsi, Dr. Pepper)
Float or Sink Candy Bars
Ivory is the soap that floats. But what about your favorite candy bar? Choose a few of your favorites, fill up a bowl or a small demo tank with water, remove the wrappers and drop them in.
We used Snickers, Three Musketeers, Hershey's Chocolate and Kit Kat bars.
The Hershey's and Snickers bars sunk like rocks to the bottom, while the Kit Kat and Three Musketeers floated at the top.
How Does it Work?
Kit Kats have a lot of space in between the chocolate and wafer cookie. Those pockets contain air, which help keep the chocolate afloat. Same is true with the Three Musketeers bar. The nougat center has a lot of air whipped into it, creating little pockets of air to keep it on the surface of the water.
The Snickers has a whipped nougat section, but the pockets of air aren't enough to overcome the density of the peanuts, caramel and chocolate. Hershey's bars have the same problem. There are a few air pockets here and there in the solid chocolate, but not enough to keep the bar from sinking.
We also cut the bars in half to see what was inside and to test whether or not having the water flood the inside would make a difference. The exposed side didn't make a difference to the buoyancy of the bar. We hypothesized that the air pockets inside were too small for the water molecules to permeate.
Try other types of candy bars or just plain candy to see what floats or sinks. Before dropping them in the water, do a little research by biting into the candy and seeing what's inside. Make a guess based on the contents as to whether the candy will float or sink.
Incredible Growing Gummy Bears
- Measure and weigh gummy (gummi) bears before starting. Use a data table to record your changes.
- Fill 3 glasses with water.
- Leave one glass alone and add about a tablespoon of salt to one and a tablespoon of sugar to the third.
- Add a few gummy bears to each glass.
- Wait about 12 hours, measure and weigh the bears.
- Check back after 24 hours, measure and weigh the bears.
- Check back after 48 hours, measure and weigh the bears.
How Does it Work?
Why do the gummy bears grow instead of dissolve in the water?
Most sugary candies dissolve when added to water. Even the candy bars in the above experiment began to dissolve after a few minutes in the water (not a pretty sight!)
Gelatin - one of the main ingredients in gummy bears - is the key.
When gummy bears are made, gelatin and water are heated, just like making Jell-O. As the mixture cools, the water is drawn out of the bears and they harden to a chewy little bear. Gelatin is a long chain-like molecule that twists and forms a solid form. As the water is removed in the cooling process, the gelatin solidifies.
A solute is the dissolved material within another material. So the gummy bear is the solute in the water. The water is the solvent. When adding salt to water, the salt is the solute and the water is the solvent.
When the gummy bears are added to water, the water molecules will move into the bear by means of osmosis. Osmosis is the movement of solvent molecules (water) through a partially permeable membrane into an area of higher solute (gummy bear/gelatin) to equalize the solute concentration on both sides.
So what does that mean? There is less water and more gelatin inside the gummy bear. There is more water outside the gummy bear. The water doesn't want to be crowded, so some of the water molecules will move inside the gummy bear where there are fewer water molecules and a lot of gelatin molecules.
The gummy bears started out with a lot of water but when they cooled and hardened, most of the water was removed.
Why does salt dissolve in water and gelatin doesn't?
Salt cannot form chains like gelatin. The gelatin molecules are are much larger than the salt. The gelatin makes the gummy bear act more like a sponge, absorbing the water instead of dissolving in it.
What happens when you add salt to the water?
The salt ions are much smaller than the gelatin molecules in the water. The salt water has about 10-20 times the molecules that is in the gummy bear. Through osmosis, the water molecules are going to move to the area with more solute or molecules in it to even out the number of water molecules in both the salt water and inside the gummy bear. The water will leave the gummy bear and move to where there are more salt molecules. The gummy bear won't shrink, so it looks like it stays the same size.
Adding extra sugar to water will cause the same effect as the salt.
Test this yourself - what happens to the gummy bears when you use tap water vs. disstilled water? Will you get different results by using a different solvent instead of water? What about soda?
Safety note - do not eat the gummy bears after they have sat in the water. When you touch them with your fingers and drop them in the water, something else is added to the water and begins to grow - bacteria.
Which Liquid Creates the Highest Mentos Geyser?
Diet Coke is the preferred soda when shooting Mentos soda geysers. But is it really the best?
Use this science fair project to determine which soda makes the best geyser.
Take a trip to your local grocery store and buy lots of soda. All different kinds and brands. Try the store brand. Try the generic. Try the brands. Collect several different types of soda and purchase two of each. You want to run your experiment twice for the sake of science.
Find a good, flat location, like next to a house or building and mark off measurements using tape on the side. You want to easily see which geysers go the highest and which ones fizzle.
Drop the same number of Mentos into each soda, one at a time, and note the height.
You may be surprised at which sodas shoot the highest. Can you figure out a common thread with the best and worst geysers?