Reduction
Reduction is a change in which a substance loses oxygen, gains hydrogen, or gains electrons.
Practice This ConceptMain explanation
Teacher explanation
Reduction is the opposite side of oxidation. In school chemistry, it is seen when oxygen is removed from a compound or electrons are gained by a substance. Reduction and oxidation usually appear together in the same reaction.
Example
When copper(II) oxide turns into copper in the presence of hydrogen, copper(II) oxide is reduced.
Simple analogy
Reduction: remove oxygen, add hydrogen, gain electrons.
Common confusion
Students sometimes confuse reduction with loss of mass or with decomposition; those are different ideas.
Exam tip
If oxygen is removed from a compound, write reduction confidently and then support it with the reason.
Answer writing and exam use
1-mark use
Write the exact meaning of reduction in one clean line.
2-mark use
Define reduction and add one example or condition.
3-mark use
Explain reduction, show the method or example, and mention the common mistake.
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