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Oxidation

Oxidation is a change in which a substance gains oxygen, loses hydrogen, or loses electrons.

In one line: Oxidation: add oxygen, lose hydrogen, lose electrons.

Understand it

In Class 10 chemistry, oxidation is easy to spot when oxygen is added or hydrogen is removed. In electron language, oxidation also means loss of electrons. Many common examples, such as burning magnesium or forming metal oxides, show oxidation clearly.

Example

When magnesium burns in air to form magnesium oxide, magnesium gets oxidized.

Rule to remember

Oxidation = addition of oxygen, removal of hydrogen, or loss of electrons.

See it worked out

Follow the example line by line, then use the same method on new questions.

Worked example

12Mg + O₂ → 2MgO.
2Magnesium gains oxygen, so magnesium is oxidized.

Method you can reuse

1Check whether oxygen is added or hydrogen is removed.
2If electron transfer is given, see whether electrons are lost.
3Name the substance as oxidized.

Sketch it in your answer

Show a simple reactant to product arrow and mark oxygen addition or electron loss above the arrow.

Check yourself

Answer the question in your head before opening the answer.

Try it yourself

A substance combines with oxygen during a reaction. What type of change is this?

Think first, then show answer

This is oxidation because adding oxygen to a substance is one of the standard signs of oxidation.

Common wrong answer

Saying the substance is reduced because it forms a compound.

Why it loses marks: Oxidation is decided by oxygen, hydrogen, or electron change, not by compound formation alone.

Don't mix this up

Students often think oxidation means only adding oxygen, but electron loss is also an important sign of oxidation.

Exam tip

In an exam answer, mention both the oxygen-based idea and the electron-based idea when possible.

Oxidation diagram

Open full screen to read every label clearly.

Write it in the exam

Each point is worth about one mark. Write point 1 for a 1-mark question and keep adding points as the marks go up.

How CBSE asks it

Students may be asked to identify oxidation in a reaction, or to state whether oxygen is added or electrons are lost.

1
Enough for 1 mark
Oxidation is a change in which a substance gains oxygen, loses hydrogen, or loses electrons.
2
Add for 2 marks
Example: When magnesium burns in air to form magnesium oxide, magnesium gets oxidized.
3
Add for 3 marks
In electron language, oxidation also means loss of electrons.

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