GCSE Chemistry 3

Question 1

Which of the following substances is a mixture rather than a pure compound?

Accepted Answer

Air

Answer

Air is a mixture of nitrogen, oxygen, argon, and other gases that are not chemically combined.

Question 2

In the periodic table, elements in the same group have the same number of:

Accepted Answer

Electrons in the outer shell

Answer

Elements in the same group share the same number of outer shell (valence) electrons, giving them similar chemical properties.

Question 3

What type of reaction occurs when iron rusts in the presence of water and oxygen?

Accepted Answer

Oxidation

Answer

Rusting is an oxidation reaction in which iron loses electrons and combines with oxygen to form iron(III) oxide.

Question 4

Which separation technique would best separate a mixture of salt and sand?

Accepted Answer

Dissolving in water, filtering, then evaporating

Answer

Salt dissolves in water while sand does not; filtering removes the sand, and evaporation recovers the salt.

Question 5

What is the pH of a neutral solution at 25°C?

Accepted Answer

7

Answer

A neutral solution has equal concentrations of H⁺ and OH⁻ ions, giving a pH of exactly 7 at 25°C.

GCSE - General Certificate of Secondary Education Practice Test