Oxidation and Reduction

Oxidation and Reduction

Oxidation

Oxidation is when a substance gains oxygen e.g. when magnesium burns it reacts with oxygen to form magnesium oxide.

Poll

Oxidation is when a substance gains ....

• oxygen

• nitrogen

Multiple Choice

Which of these reactions is oxidation occurring in ?

• Magnesium + oxygen

• magnesium sulphate + iron

• copper + oxygen

Other examples of oxidation reactions include ....

Combustion (posh science word for burning)

Rusting - Iron reacts with oxygen in the air

Respiration - glucose reacts with oxygen that we breathe in

Another meaning of oxidation

Chemists also use oxidation to describe a reaction in which a substance loses electrons

Multiple Choice

If an atom loses two electrons what charge will it have?

• +1

• -2

• -1

• +2

Reduction

If a substance has oxygen removed from it then we say that substance has been reduced. We tend to use this word when describing how metals are extracted from metal compounds.

For example

Iron oxide reacts with carbon . Carbon is more reactive than iron so DISPLACES iron. This has the effect of removing oxygen from iron oxide.

Multiple Choice

Which of the word equations below shows the reduction of iron oxide when it reacts with carbon

• iron oxide + carbon (changes into) iron + carbon dioxide

• iron +carbon dioxide (changes into) iron oxide + carbon

• iron oxide (changes into) carbon dioxide

Reduction is a term also used to describe a reaction in which an atom gains electrons

Multiple Choice

When an atom gains electrons what will be the charge on the ion which is formed?

• positive

• negative

Multiple Select

When an atom gains one electron to form a full outer shell what charge will the ion have?

• +1

• -2

• -1

• +2

Summary

Oxidation occurs when a substance gains oxygen.

Oxidation can also be used to describe a reaction in which an atom loses electrons.

Reduction occurs when oxygen is removed from a substance.

Reduction can also be used to describe a reaction in which an atom gains electrons.