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Melting and freezing
Words to learn: physical change • reversible • state • shape
If a material looks different, has it necessarily become a new material?
Same material, different state
Ice can melt and water can freeze; chocolate can melt and harden. The state changes, but the material itself has not become a new substance.
Shape can change too
Metal can be bent, glass can be shaped while hot, and many materials can be cut or moulded. Changing shape does not necessarily change what the material is made from.
Getting a material back
Dissolving can also be reversible. If sugar is dissolved in water, evaporating the water can leave the sugar behind. A useful test is to ask whether the original material can be recovered.
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Where does this mystery belong?
CHANGING MATERIALS — TEXTBOOK PAGES TO BE LINKED. Textbook spread and protected page link to be added.
Who uses this knowledge?
