What is your favorite type of candy? Have you ever wondered why you like this candy so much? Is it its taste, how it feels in your mouth—or both?
Cooks and food scientists study how substances dissolve or melt to create a unique and pleasant sensation in the mouth and optimize the release of flavor. Would you like to know how your favorite candy works? In this science activity you will study two types of candy and discover what makes them so enjoyable.
The digestion of food is one big chemical process. It starts in our mouths where saliva—a watery liquid—surrounds the food. Saliva helps us to chew and swallow food and contains a small quantity of enzymes, or chemicals that help break down our food. How a food interacts with saliva will influence how it tastes as well as how it feels in the mouth. Will it dissolve, will it melt or will it just be chomped into pieces by our teeth?
Whether a solid dissolves when surrounded by water depends on how strong the internal bonds are and how eager it is to bond with water. For example, to dissolve sugar in water, bonds between sugar molecules (the tiniest sugar particles) and between water molecules (the tiniest water particles) must be broken. This requires energy. Luckily the creation of new bonds between sugar and water releases enough energy to break those bonds so sugar can dissolve in water. If the released energy is less than the energy required, however, the solid will not dissolve.
Temperature plays a role as well. Adding heat means adding energy—and for most solids the hotter the water, the easier and faster it is to dissolve the solid. Heated molecules move around more so the dissolved substance will disperse more quickly than in unheated water.
Most candy contains sugar and/or corn syrup as a sweetener with a few other ingredients to add flavor and texture. Hard rock candies, such as fruit drops, are mainly crystalized sugar that dissolve when surrounded by saliva. For soft candy, such as gummy bears, gelatin is often used to create their particular texture. Gelatin is derived from collagen, which is a structural protein found in all animals. Gelatin protein gets tangled when cooked, creating mesh pockets that trap water and other ingredients. After gelatin cools the proteins remained tangled and provide structure that holds many desserts or candies together. For most types of gelatin, their melting point is below body temperature, so they melt in the mouth and provide unique sensations.
- Four glasses
- Cold water
- Hot water
- Sticky notes
- Gummy bears
- Hard candy, such as fruit drops
- Two timers or a clock
- Two plates
- Work space that can tolerate spills
- Ruler (optional)
- Protect your work space for splashes of water.
- Fill two glasses each with one third cup of cold water.
- Label two sticky notes with “Cold Water” and two more with “Hot Water.”
- First, we will observe what candy does when placed in cold water. Place two gummy bears in the first glass of water.
- Then remove the wrappers of two hard candies, and place them in the second glass.
- Identify this row of glasses with a sticky note reading “Cold Water.”
- Set the first timer to 30 minutes or use the clock to track 30 minutes.
- What do you think will happen to the candy if left untouched for 30 minutes? Why do you think this will happen, and will the water change?
- While you are waiting fill the two additional glasses with one third cup of hot water. (Be careful not to get any hot water on your hands.)
- Carefully place two gummy bears in the first glass.
- Then remove the wrappers of two hard candies and place them in the second glass.
- Identify this row of glasses with a sticky note reading “Hot Water.” Set the second timer to 30 minutes or use the clock to track 30 minutes.
- What do you think will happen to this candy if left untouched for 30 minutes? Do you expect it to be different from the candy in the cold water? Why would this be the case? Do you expect the water to change?
- Label one plate “Cold Water” and the other “Hot Water.”
- After the first 30 minutes are over, it is time to observe the candy submerged in cold water. Use a spoon to carefully pick the candies out of the two glasses in the Cold Water row and place them on the plate labeled “Cold Water.” Set aside.
- For each of these cold water glasses, take a clean spoon to stir the water, scoop up a sample and taste it. Which one is sweetest?
- Take a fresh gummy bear and a hard candy out of the bag (removing the wrapper if needed), and place the candy next to the candies that have been soaked for 30 minutes. What differences do you observe? Is what you observe consistent with what you expected? If it is different, why do you think this is the case?
- Looking at the change in the size of the candies and the taste of the water, what do you think happened to each type of candy when submerged in water?
- After the second timer goes off and the Hot Water row candies have been submerged for 30 minutes, repeat the observation procedure for these candies. Remember to use the plate labeled “Hot Water” this time.
- Now that we have seen what cold and hot water does to these types of candy, let us look closer at the influence of temperature. How is the candy soaked in hot water different from the same type of candy soaked in cold water? Why do you think this has occurred?
- Pop a fresh candy from the bag into your mouth. Notice how your mouth is a watery environment that is at body temperature. How do you think your previous observations relate to the feel and taste of the candies in your mouth?
- Extra: Use a ruler to measure the lengths of the unsoaked and soaked candies, then express the change as a percentage. Can you estimate the change in volume as well? You can also compare the sizes of the candies soaked in hot water with those soaked in cold water.
- Extra: Study the influence of heat further by filling a glass with one third cup of ice-cold water and another glass with one third cup of hot water. If possible, place the hot water glass in a hot water bath, so the water does not cool off as fast. Put a brightly colored hard candy in each glass and watch how the color spreads in each glass. Which one spreads faster? Why do you think this happens?
- Extra: Study the effect of additives such as salt or sugar in the water. Would a gummy bear soak up more, less or an equal amount of water if soaked in a salty or sugary solution compared with tap or distilled water? Why do you think this happens?
- Extra: Add chopped pieces of fresh tropical fruits such as pineapple, kiwi or papaya to the water. Would the gummy bears dissolve differently when these fruits are added to the solution? What about if we add apple, lemon or orange slices? (Hint—think of gelatin desserts and why certain fresh foods cannot be added to them.)
Observations and results
Did you see that the hard candies dissolved in cold water whereas the gummy bears puffed up? Did hot water dissolve the hard candies faster whereas the gummy bears started to melt in the hot water?
Hard candy is often made primarily of sugar, corn syrup and other substances that dissolve easily in water. Like the saliva in your mouth, the water in the glass allowed them to dissolve. Adding heat made this process easier and faster. As the candy dissolved layer by layer, it got smaller and smaller, and more and more sugar, syrup and flavor chemicals dispersed in the water. That is why the water tasted sweet, like the candies.
Gummy bears, on the other hand, contain gelatin, which gives it its typical soft texture. The gelatin creates a mesh of entangled long molecules that hold the gummies together. The structure has pockets that can absorb water via a process called osmosis. That is why the gummies swell up when soaked in cold water. The water stays relatively tasteless. It was different when you submerged the gummies in hot water. Because the temperature of the hot water was above the gelatin’s melting temperature, the outer layer of the gummies melted away. The gummy bears got smaller and smaller, and you could see tiny pieces of gummy bear floating in the water. These pieces make the water taste sweet, like the gummy bears.
Hot water molecules move around more so you will see that the color disperses more in hot than cold water. Fresh papaya, pineapple and kiwi contain enzymes that break down gelatin. The addition of these and a few other enzyme-containing fruits can make your gummy bears break down.
Throw away soaked candy and wash all equipment with soapy water.
More to explore
Solubility Science: How to Grow the Best Crystals, from Scientific American
Solidifying Science: Why Can Certain Fruits Ruin Your Gelatin Dessert?, from Scientific American
Salty Science: How to Separate Soluble Solutions, from Scientific American
This activity brought to you in partnership with Science Buddies