GCSE ChemistryCombined and separate
Practise GCSE Chemistry with questions on every topic, from atoms and the periodic table to the atmosphere, and calculations with every step of the working shown.
The questions on this page come from the Show Working app, where Science is on its way. Each has the answer, the reason, and the trusted source we checked it against.
Where is most of the mass of an atom?
An atom has a tiny, positively charged nucleus at its centre, made of protons and neutrons. Almost all of the mass is there. Negatively charged electrons move around the nucleus in shells.
01 / TopicsFrom the national content
Atoms and the periodic table, bonding, structure and properties, chemical changes, energy changes, rates and equilibrium, organic chemistry, chemical analysis, chemical and allied industries and Earth and the atmosphere. They follow the Department for Education’s GCSE chemistry content, which every board in England teaches.
Facts marked separate Chemistry only don’t come up for Combined Science pupils, and Higher-only facts don’t come up on Foundation. In the app, your board, course and tier decide which you see.
02 / Sample questionsOne from each topic
Chemistry marks come from two places: knowing facts and tests exactly, and doing calculations with the working shown. The app practises both, with the reason for every fact and every step of every calculation.
01 / Atoms and the periodic tableBoth tiers
Answer: B In the nucleus
An atom has a tiny, positively charged nucleus at its centre, made of protons and neutrons. Almost all of the mass is there. Negatively charged electrons move around the nucleus in shells.
Checked against AQA GCSE Chemistry 8462 specification, 4.1.1.5 Size and mass of atoms
02 / Bonding, structure and propertiesBoth tiers
Answer: D Close together in a regular pattern
In a solid, particles are packed in a regular pattern and vibrate in place. In a liquid, they are still close but move around each other. In a gas, they are far apart and move quickly in all directions.
Checked against Pearson Edexcel GCSE Chemistry 1CH0 specification, 2.1 States of matter
03 / Chemical changesBoth tiers
Answer: C Cl₂
An element contains only one kind of atom, so its formula has only one symbol. Hydrogen, oxygen, nitrogen and the halogens exist as molecules of two atoms, so they are written H₂, O₂, N₂ and Cl₂.
Checked against OpenStax Chemistry 2e, 2.4 Chemical Formulas
04 / Energy changesBoth tiers
Answer: B It rises
An exothermic reaction transfers energy to the surroundings, so the temperature of the surroundings goes up. A thermometer in the reaction mixture shows a rise.
Checked against AQA GCSE Chemistry 8462 specification, 4.5.1.1 Energy transfer during exothermic and endothermic reactions
05 / Rates and equilibriumBoth tiers
Answer: B A precipitate of sulfur forms
The reaction makes a precipitate of sulfur, so the mixture goes cloudy and hides the cross. The shorter the time for the cross to disappear, the faster the reaction. This is a way to follow a reaction by watching it go cloudy.
Checked against Royal Society of Chemistry, The effect of temperature on reaction rate
06 / Chemical analysisBoth tiers
Answer: A A single element or compound
In chemistry, a pure substance is a single element or a single compound, not mixed with anything else. In everyday use “pure” means natural or with nothing added, so pure orange juice is still a mixture of water, sugars, acids and more.
Checked against AQA GCSE Chemistry (8462) specification, 4.8.1.1 Pure substances
07 / Chemical and allied industriesBoth tiers
Answer: A A compound of hydrogen and carbon only
A hydrocarbon is a compound of hydrogen and carbon only. Alkanes are a homologous series: they share a general formula, have similar chemical properties and each differs from the next by CH₂. They are saturated because they have only single bonds between carbon atoms.
Checked against OpenStax Chemistry 2e, 20.1 Hydrocarbons
08 / Earth and the atmosphereBoth tiers
Answer: D Methane
Carbon dioxide, methane and water vapour are greenhouse gases; nitrogen and oxygen are not. A natural greenhouse effect keeps the Earth warm enough for life. The problem is that extra greenhouse gases from human activity are making the effect stronger.
Checked against Met Office, Causes of climate change
03 / Chemistry calculations35 kinds, fresh numbers every time
Every kind of calculation makes new numbers each time you practise, and shows the working step by step: the equation, the numbers in, the rearranging and the unit. The answers are worked out by code, never typed.
Work out the percentage by mass of carbon in carbon dioxide, CO₂.
Relative atomic masses (Aᵣ): C = 12, O = 16
Answer 27.3%
A technician dissolves 18 g of sodium hydroxide in water to make 0.25 dm³ of solution. Work out the concentration of the solution in g/dm³.
Answer 72 g/dm³
04 / Required practicals11 practicals across the boards
Practical work is at least 15% of the marks. Here’s every chemistry practical AQA or Edexcel requires, plus OCR’s practical groups, with who has each one. Open one for the variables, the method, a safety point and where the marks go.
Questions from the app’s required practicals topic, with the answer and the reason.
01 / Required practicalsBoth tiers
The right order: C, B, D, F, A, E
The base goes in until no more reacts, so all the acid is used up. Filtering removes the leftover solid. Some water is evaporated, then the solution cools and crystals of the salt form.
Checked against AQA GCSE Chemistry 8462 specification, 8.2.1 Required practical activity 1 (with 4.4.2.3 Soluble salts)
02 / Required practicalsBoth tiers · separate only
Answer: B So leftover water does not dilute it
Water left in the burette would dilute the acid, so more would be needed. Water in the conical flask does not matter: the pipette still delivers the same amount of alkali, and that is what the acid neutralises.
Checked against AQA GCSE Chemistry 8462 specification, 4.4.2.5 Titrations and Required practical 2
03 / Required practicalsBoth tiers
Answer: C One reactant has been used up
The gradient of the line shows the rate. It is steepest at the start, when the reactants are most concentrated. As they are used up it gets less steep, and it is flat once one reactant has run out.
Checked against AQA GCSE Chemistry 8462 specification, 4.6.1.1 Calculating rates of reactions
04 / Required practicalsBoth tiers · separate only
The right order: B, A, C, D
Tap water contains dissolved ions such as chloride, which would give their own results. The acid removes carbonate ions, which would also form a precipitate, and the colour of the silver halide precipitate shows which halide is there.
Checked against AQA GCSE Chemistry 8462 specification, 4.8.3 Identification of ions and Required practical 7
05 / Long answers6 marks
In the app you write your answer, then tick off what a full answer includes and read our model answer. No AI marking, no score, no grade.
Explain how the meaning of “pure” on the carton differs from its meaning in chemistry, and describe two ways the chemist could check whether the aspirin is pure.
06 / Coming to Show WorkingWhat it will cost
We’re building Science for Show Working now, and chemistry is part of it. It isn’t on phones yet, and we won’t give a date until it’s ready.
Maths is the subject in Show Working today: fresh questions every time, with the working shown for every answer. See the maths topics.
Coming soon to the App Store07 / QuestionsAbout GCSE Chemistry
Show Working groups the Department for Education’s chemistry content into nine areas: atoms and the periodic table; bonding, structure and properties; chemical changes; energy changes; rates and equilibrium; organic chemistry; chemical analysis; chemical and allied industries; and Earth and the atmosphere.
No. Every board gives you a periodic table in the exam. You do need to know how to use it: what the groups and periods tell you, how to find the number of protons, and how to read relative atomic masses.
At least 20% of the marks are for maths skills. Common calculations include relative formula mass, percentage by mass, concentration, rates and Rf values, plus moles on Higher and yield and atom economy in separate Chemistry.
AQA has 8 for Chemistry and 6 chemistry ones in Combined Science. Edexcel has 8 core practicals in Chemistry and 5 in Combined Science. OCR sets practical activity groups and lets schools choose the experiments.
Cover, recall, check.
Read the answers today, then come back tomorrow, cover them and see how many you still know. That’s how facts stick.
Revise the practicalsWant the bigger picture? Combined or separate, boards and tiers.
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