PassNova has 13 free KS3 Science practice questions on Chemistry, each with a clear explanation. Practise them in the browser with instant feedback — 100% free, no sign-up, on any device. Updated for 2026.
Chemistry: example questions & answers
12 worked examples with answers and explanations below. Practise all 13 Chemistry questions free in the browser, with instant feedback on every answer.
What are the three states of matter?
- AHot, warm, cold
- BSolid, liquid, gas✓
- CHard, soft, runny
- DBig, medium, small
Answer: Matter usually exists as a solid, a liquid or a gas.
In which state are the particles packed closely together and vibrating in fixed positions?
- AGas
- BLiquid
- CSolid✓
- DPlasma
Answer: In a solid, particles are tightly packed in a fixed arrangement and only vibrate.
What is the smallest part of an element?
- AA cell
- BAn atom✓
- CA mixture
- DA compound
Answer: An atom is the smallest particle of an element that still has its properties.
Water is made of hydrogen and oxygen joined together. Water is therefore a:
- AMixture
- BCompound✓
- CSingle element
- DMetal
Answer: A compound is formed when two or more elements chemically bond — H₂O is a compound.
What colour does universal indicator turn in a strong acid?
- APurple
- BGreen
- CRed✓
- DBlue
Answer: Universal indicator turns red in a strong acid (low pH).
On the pH scale, a neutral substance like pure water has a pH of:
- A0
- B7✓
- C14
- D1
Answer: pH 7 is neutral; below 7 is acidic and above 7 is alkaline.
Which process turns a liquid into a gas?
- AFreezing
- BMelting
- CEvaporation✓
- DCondensation
Answer: Evaporation (or boiling) changes a liquid into a gas.
What is formed when a metal reacts with oxygen?
- AA metal oxide✓
- BA salt
- CWater only
- DA gas only
Answer: Metals react with oxygen to form metal oxides (e.g. iron + oxygen → iron oxide/rust).
The rows in the Periodic Table are called:
- AGroups
- BPeriods✓
- CColumns
- DFamilies
Answer: Horizontal rows are 'periods'; vertical columns are 'groups'.
Which of these is a chemical change (not a physical one)?
- AMelting ice
- BBurning wood✓
- CCutting paper
- DBoiling water
Answer: Burning wood makes new substances and is irreversible — a chemical change.
A mixture of sand and water can be separated by:
- AFiltering✓
- BMagnetism
- CBurning
- DFreezing
Answer: Filtering traps the insoluble sand and lets the water pass through.
Which gas makes up most of the air we breathe?
- AOxygen
- BCarbon dioxide
- CNitrogen✓
- DHelium
Answer: About 78% of air is nitrogen; oxygen is around 21%.