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Question
Is a change of state of matter – a physical or a chemical change. Give reasons.
Solution
- There are three different states of matter: solid, liquid, and gas. The transition between various states, such as solid to liquid (melting), liquid to gas (boiling), and vice versa (freezing and condensation), is referred to as a change of state.
- Take water (H2O) as an example. There are three states of water: As a solid (ice), a liquid (water), or a gas (steam).
- Water becomes ice (solid) when it freezes. Ice melts and returns to liquid form as water. Water transforms into steam (gas) when it boils. Steam condenses back into liquid water when it cools.
- The chemistry of water (H2O) remains unchanged during these modifications. The actual chemical identity of water remains unchanged; the molecules are merely rearranged.
- We categorize the change of state of matter as a physical change as the substance's chemical makeup does not alter throughout the transition. Even though a substance undergoes a physical change, its chemical identity is unaffected.
- The change of state of matter is a physical change because the chemical composition does not alter; it remains H2O in all states.
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