Which of the following is a chemical change?
Combustion of petrol
Correct Answer: Combustion of petrol
A chemical change produces new substances with different properties and is generally irreversible.
- Combustion of petrol: C₈H₁₈ + O₂ → CO₂ + H₂O + energy → chemical change ✓
- Mixing salt and water → physical change (can be recovered by evaporation)
- Evaporation of water → physical change (state change only)
- Ice melting → physical change (state change; water is still H₂O)
Signs of chemical change: new substance formed, energy change, colour/smell change, gas/precipitate produced.
Similar Questions
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\(3\,\text{MnO}_2\,(s) + x\,\text{Al}\,(s) \rightarrow 3\,\text{Mn}\,(l) + y\,\text{Al}_2\text{O}_3\,(s) + \text{Heat}\)
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Fe + H2O4 → Fe3O4 + H2
Which statement best explains why this step is INCORRECT?
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Important Questions from Chemical Reaction
Which of the following statement is/are true?
I. In physical change new substance is formed. substance is formed.
II. In chemical change no new substance is formed.
Which of the following cells involves similar chemical reactions?
The information not obtained from balanced chemical equation is
Oxygen cannot be obtained by which one of the following methods?
Which of the following compound is responsible for tarnishing of silver?
