Your teacher is holding up an ice cube and a square of chocolate. What do you think will happen if we warm them gently? And once they have changed, can we ever get them back the way they were?
Reversible: a change you can undo so the original material comes back. Irreversible: a change you cannot undo because a new material has been made. Melting: a solid turning into a liquid when it is heated.
Watch the ice melting in the dish at the front. Which do you think melting ice is: reversible or irreversible?
We will warm ice and chocolate in a gentle warm-water bath. Before anything goes in the water, open your Investigation Journal page. Write one prediction for ice and one for chocolate: will each melt, and can we get the solid back again? Talk with your group, then be ready to share one prediction.
Work through the stages on the card below with your group. Hands off the ice, the chocolate and the melt liquid, and no tasting.
Write what you see on your Investigation Journal page as you go: which melts first, and whether each is solid or liquid, clear or brown, soft or runny.
Before the toaster starts, write one prediction on your Investigation Journal page: what will happen to the bread, and could we ever turn it back into soft white bread? Then watch the demonstration carefully.
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