Popsicle Science

Practice observation, measurement and other skills while you learn about freezing rates of different liquids!

Cooking activities are great for teaching kids how to use measurement tools, giving them a chance to apply math skills like counting, adding, multiplying, etc. In addition, when you give them a chance to design their own recipe, kids have to rely on estimation, problem solving and other science, math and engineering skills.

Preparation

Ice cube trays come in many shapes and sizes. If you can find trays that make smaller cubes, they will be more effective for this activity—the larger the cube, the longer you’ll have to wait for it to freeze! You can buy ingredients ahead of time for the freeze test described below, or you can brainstorm a list with your kids one day, shop for what they come up with and conduct the experiment another day.

Gather lots of different kinds of drinkable liquids and other edible substances that seem appropriate (some foods like whipped cream and peanut butter seem sort of like a liquid and sort of like a solid—both are delicious). The more different kinds of ingredients you have, the better the experiment will be. Make sure that all ingredients are the same temperature—you can do this by putting them all in the refrigerator overnight before you use them, or leaving them all out at room temperature for a few hours. When you have all of your ingredients, separate them into several cups so that materials can be shared. You’ll want 2–3 cups of each ingredient.

Suggested Materials

Ice cube trays (1 per team)
Many different kinds of drinkable liquids or other ingredients, especially real fruit juices (ex. orange and apple juice, soda, milk, cream, peanut butter, whipped cream, vegetable oil, etc)
Clear plastic wrap
Toothpicks
Cups (100)
Spoons
Newspaper
A freezer

Optional Materials

Eyedroppers

Opening Discussion

Ask your students if they have ever had popsicles before. What kinds of ingredients are in popsicles? What are their favorite flavors? Tell them that you would like them to invent their own popsicle recipes, but before they do, they need to figure out what ingredients will work best. Have them brainstorm a list of ingredients they would like to test. If you’ve chosen to do the testing right away, tell your students that before they create their recipes, they’ll be testing lots of different liquids and other ingredients to see how they freeze. If you choose to have a set of ingredients that more closely resembles their brainstorm list, tell them that you’ll need to purchase their requested ingredients and that they’ll be testing these ingredients another day.

The Challenge

Does everything freeze at the same rate, or do some substances freeze faster or slower than others? Are there some that won’t freeze at all? Test your ingredients and find out the answer!

Doing the Activity

Separate children into teams of 2 or 3.
Have each team choose 3-6 of the ingredients you have separated into cups. These will be their testing ingredients. Since most ice cube trays have 12, 16, 36…up to 90 cubes, you should consider having teams share trays. This will save space in your freezer and will cause the freezer door to be opened and closed less frequently.
Once teams are all settled and everyone knows which teams are sharing trays, have them fill their tray compartments with the ingredients they chose, being careful to add the same amount to each compartment. Teams will need to make a “map” of their ice cube trays, noting which liquids are where in the tray.
Once the trays are filled, place a sheet of plastic wrap over each tray and have your students carefully poke a toothpick into each cube compartment—these toothpicks will be the “handles” of their mini popsicles. The plastic wrap helps keep the toothpicks upright. You could have each team create small flags or other markers and attach them to the toothpicks, marking what ingredient is in each cube.
Place the trays in the freezer, and check them every 15 minutes or so. The most efficient way to accomplish this is for you to take every tray out, put them on the table and have each team record their observations.

Let’s Talk About It

After you’ve placed the trays in the freezer, ask your students to predict what will happen. How long will it take for the ingredients to freeze? Will some not freeze at all? Will some freeze faster or slower? Make a list of the ingredients that they predict will be “Fast Freezers”, “Slow Freezers”, and “No Freezers”.

Build On What They Talked About

Keep checking on the popsicles, and have your students write down their observations. While they wait, you can have them develop a recipe to test out during the next session. Tell them that they can mix ingredients up, and that they’ll also have sugar, honey and food coloring to use. What flavors might go well together?

When the cubes are all (or mostly) frozen, have your students take them out and (if you would like) taste them. What do they notice about their popsicles—do they look bigger, smaller or the same size in the tray as they did when they were just liquid? Do they taste different or the same as they did unfrozen? Will this change their choices of ingredients for their recipes?

Suggestions

If you are using mini-ice cube trays, they will begin freezing in 15 minutes or so, and will be fully frozen in 45 minutes. Large ice cube trays take longer.
After trying this activity, give kids a chance to create their own popsicle recipes in the Popsicle Science – Invent Your Own activity.