lesson
Heating and cooling can change state
1 · Learn
Melting changes a solid to a liquid; freezing changes a liquid to a solid. Pure water melts or freezes around 0°C at ordinary pressure. Different substances have different melting temperatures.
Temperature is measured in degrees Celsius. A warmer room can transfer energy to an ice cube so it melts. The liquid water has not disappeared or become a new substance.
2 · Worked example
An ice cube left in a suitable tray changes into liquid water. I describe the state change and record conditions rather than calling it dissolving.
3 · Your turn
What is the change from liquid water to ice called? Does every solid melt at 0°C?
Check your answer
Freezing. No: different substances have different melting temperatures.
4 · Apply your learning
With an adult, observe ice in a tray over time and record its state. Research other melting temperatures from reliable references rather than heating unknown materials.
Adult guidance and safety
Adults handle thermometers and any cooling equipment. No boiling liquids, flames, tasting, dry ice or sealed heating experiments.
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My observation notebook
With an adult, look at a safe real example or a checked photograph. Name the example and say which you used. Record what you actually notice. Do not taste plants or materials, approach unknown animals or invent missing observations.
Ask your teacher for support with the method and recording. A prediction is what you think might happen; an observation is what you actually see, hear or feel safely.
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