Melt or Not?

Hook 5 min

1. Point at the ice cube. "What is happening to our ice cube?" (It's melting.)
2. "When it's all water, could we ever get our ice cube back? How?" Take a few ideas. Don't settle it.
3. "Today we're scientists. We'll change things with heat and cold, then test if the change can go back."

Explore 15 min

Every object has four steps, shown by the bar at the top: change it, predict, test, sort.

1. An ice cube. Press Warm it up. "Can the puddle change back into ice?" Partners talk, then thumbs up for Can go back, thumbs down for Can't go back. Tap the bin the class picked, then press Put it in the freezer to test it.
2. A slice of bread. Same steps. Before the test, ask: "If we put the toast in the fridge, will it turn back into bread?" (No. It stays toast.)
3. A chocolate bar, A raw egg and A cup of orange juice. Let partners whisper a prediction before every vote. The juice is cooled first, so its test is to leave it in the sun.
4. When a test doesn't match the vote, the tool says Surprise! Stop there: "What did the test show us? Why didn't we expect it?"
5. Keep going with Next thing: popcorn, butter, cake batter, clay, paper. For the paper, remind the class that burning is only for grown-ups.

Make sense 8 min

1. Look at the Can go back bin. "What do these have in common?" (They melted or froze, or just changed shape.)
2. Look at the Can't go back bin. "What happened to all of these?" (They were cooked, baked, popped or burned. Something new was made.)
3. Teach the frame for an argument, and model it with chocolate: "I think chocolate can go back, because when we cooled it, it turned solid again." The test is the evidence.
4. Partners use the frame for one object each. Call on two or three pairs.

Apply 7 min

1. Name an object the tool didn't have. Children stand up if they think the change can go back, and stay sitting if it can't.
2. Use a crayon melted in the sun (can go back: it hardens again, in a new shape), a cracker toasted in a toaster (can't), a snowman melting into a puddle (the water can freeze again, but not into a snowman), and a pancake on a hot pan (can't).
3. After each one: "Who can give me a because?"

Exit check 5 min

1. Back to the plate. "Our ice cube is water now. Can it go back? How could we test it?" (Freeze it.) Put the plate in a freezer and check it tomorrow.
2. Each child tells their partner one change that can go back and one that can't, with a because. Listen in on four or five pairs. Those without a because need the frame again tomorrow.