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Question
Give one example of a chemical reaction characterised by a change in state.
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Solution
The combustion reaction of candle wax is characterised by a change in state from solid to liquid and gas.
When a wax candle burns, the solid wax reacts with oxygen to form carbon dioxide gas and water. At room temperature, candle wax is a solid, the carbon dioxide formed is a gas, and the water formed by the combustion is a liquid. Therefore, the physical state changes from solid to liquid and gas.
\[\ce{Wax_{(solid)} + O2_{(g)} -> CO2_{(g)} + H2O_{(l)} + Heat + Light}\]
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