Lemon Freeze

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Lemon Freeze
  • Age: 8+
  • Time: 240
  • (Setup: 15 min, Activity: 30 min, Cleanup: 15 min)
  • Materials: $8

In this cooler-than-cool-it’s-frozen mission, you’ll find out that how you process things can lead to creating all-new properties. To do this, you’ll be making two types of yummy lemon ices to see what happens when we assist in breaking up molecules—and when we don’t!

Download PDF
  • what you need
    WHAT YOU NEED

    Materials:

    • Masking tape
    • 3-4 lemons
    • 4 cups hot water
    • 1 cup sugar

    Equipment:

    • ½  cup measuring cup
    • Grater or lemon zester
    • Ice cube tray or muffin pan
    • Mixing bowl
    • Small stirring spoon
    • Knife
    • Pen

    Note: The printable PDF for this experiment includes a data sheet for marking observations.

  • What To Do
    WHAT TO DO
    1. First prepare the ingredients. With help from a grown-up, mix the hot water and sugar in a mixing bowl, stirring with a spoon until all of the sugar is dissolved. Put this mixture in the refrigerator for about one hour. While your sugar water is chilling, use a grater to grate 1 teaspoon lemon rind. Be sure to grate only the outer yellow surface of the lemon, the white stuff below tastes bad! Then cut the lemons in half with the knife and squeeze them over a measuring cup to make ½ cup of juice. Be sure to remove any seeds that sneak in. Add the grated rind to this lemon juice.
    2. Prepare your ice cube trays or muffin pan. You will make two types of lemon ices: “A – Still” and “B – Stirred”. Use the masking tape and pen to label half of your tray or pan with an “A – Still” and the other half with a “B - Stirred.”
    3. After an hour, add the lemon mixture to the cooled sugar water and stir. Pour the mixture into your prepared tray or pan, filling each compartment about ¾ full. Save any leftover mixture in the refrigerator for further experiments!
    4. Put the tray in the freezer and wait 30 minutes. While you’re waiting, write down what you think you’ll see when you remove the tray.
    5. Now remove the tray and observe what has happened. Has anything changed? Write down your observations, and then use the spoon to stir each of the compartments on the “B – Stirred” side, scraping the edges of the compartment as you stir. Do not disturb the “A – Still” side. Place the tray back into the freezer for 30 minutes.
    6. Continue stirring the “B - Stirred” side every 30 minutes for approximately 3 hours, or until both types are frozen. Make observations each time you take the tray out. When do the ices start to become solid? What changes occur? Which completely freezes first?
    7. Now eat your ices. How do they taste?

    Cleanup: After enjoying your lemon desserts, wash your dishes and tray or pan.

  • What's Happening?
    WHAT’S HAPPENING?

    You may have noticed that you made two completely different consistencies of dessert! Although you used the exact same materials, the different processes you used caused a big change in their properties. When the lemon mixture is in its liquid form, its molecules are free to move. As it freezes, the water molecules slow down and start to form tiny ice crystals. The crystals get bigger as more molecules join them, and eventually you get one big block of ice, like a popsicle. Stirring the lemon mixture during the freezing process changes how the molecules are arranged, resulting in smaller crystals and a softer texture like a slushy. While we cannot see these atomic structures with our eyes, the different textures show us the behaviors they cause.

  • So What?
    Photo of five small bottles of liquid, glowing red, orange, yellow, green, and blue against a black background.

    Image credit: Travis Jennings

    SO WHAT?

    Materials scientists are always experimenting to find new properties of materials. As we saw in our experiment, sometimes you can find new properties from the same materials just by changing how you put them together. For example, scientists build solid structures of special types of atoms called semiconductors, because they conduct electricity when they are all packed together. If you put the same atoms together as tiny particles—thousands of times smaller than a grain of sand—they act very differently. Called “quantum dots,” these semiconductor particles glow different colors depending on their size.

  • Scientists In Action
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    Scientists In Action

    For Kathy Gehoski and Richard Wiencek, becoming a materials scientist wasn’t always part of the plan. Today, as they explore new ways of creating materials, they love seeing their science pop up in everyday places.