Curriculum
Science — Second Preparatory
Unit 1: Matter and Energy
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Unit 2: Matter and Chemical Reactions
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Unit 3: Energy Flow in Photosynthesis and Respiration
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Unit 4: Geological Processes
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Text lesson
Chemical Reactions
Chemical Reactions
Chemical change and physical change
Chemical change and physical change
| Comparison | Physical change | Chemical change (reaction) |
|---|---|---|
| Chemical composition | Does not change | Changes |
| Example | Sugar dissolving in water, ice melting | Burning paper, rusting of iron |
| Easy to reverse? | Usually yes | Usually difficult |
- When sugar dissolves in water, the sugar is still sugar.
- When wood burns, new substances such as ash, carbon dioxide and water vapour are formed.
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