Difference btwn Physical & Chemical Changes
Chemistry: Cambridge International GCSE Supplement, topic 6.1.1
Differences between Physical & Chemical Changes
Physical changes form no new substance and are often reversible, whereas chemical changes form new substances and are usually not reversible.
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Changes in matter
- Everything around us can undergo a change.
- This can be as simple as melting ice or as complex as a fire.
- There are two main types of changes:
- Physical changes
- Chemical changes
Physical changes
- A physical change is a change in the form or appearance.
- The substance's chemical identity does not change – It is still the same substance.
- Molecules stay the same, only the arrangement changes.
- Changes are often reversible.
- Examples:
- Ice melting into water
- Water boiling to steam
- Sugar dissolving in water
Chemical changes
- A chemical change is a process where a new substance is formed.
- The substance's chemical identity changes.
- The atoms and molecules rearrange to form something new.
- Chemical changes are usually not reversible.
- Examples:
- Burning wood to ashes: Ash cannot be turned back into wood.
- Iron rusting: It is difficult to reverse the rusting process.
- Baking a cake: The ingredients make a completely new substance.
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What is the main difference between a physical and a chemical change?