1 - Getting Started ~5 mins
Look at this piece of soft bread and this slice of toast. Could you turn the toast back into soft bread? Why or why not?
Today we will test four real changes and decide which ones we can undo, and which ones make something new.
2 - Changes We Can Undo, and Changes We Cannot ~6 mins
Today’s two big words:
Reversible — a change you can undo and get the same material back.
Irreversible — a change that makes something new and cannot be undone.
When ice melts into water and then freezes again, is that reversible or irreversible?
3 - What Do You Think Will Happen? ~5 mins
We will test four changes: melting chocolate then cooling it, dissolving salt then letting the water dry, mixing baking soda with vinegar, and toasting bread.
With your group, predict for each one: can we undo it, or does it make something new? Be ready to share one prediction and why. Think what you will look for — that will be your evidence.
4 - Station Investigations ~18 mins
Your group will visit the change stations. At each one, carry out the change carefully, watch closely, and talk about whether you think you can undo it.
Station A: melt a small piece of chocolate on a warm lid, then cool it on a chilled plate. Station B: dissolve salt in water, start drying a drop, and compare with the labelled “salt came back” sample. Station C: mix baking soda with vinegar. Then watch the toast demo together.
No tasting. Keep vinegar mixes away from eyes and faces.
5 - Record What We Observed ~8 mins
Open your Investigation Journal page and answer the three questions with what you saw at the stations: Which changes gave the same material back?, Which changes made something new? and What evidence did you use? Name all four changes across your answers.
Use evidence: what you saw, heard or felt. Keep “what we saw” separate from “what we think it means”.
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