OCR GCSE Chemistry A, Foundation tier sample questions and answers (J248)
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30 sample questions and answers
Taken from every topic of OCR GCSE Chemistry A, Foundation tier, specification J248. The full guide has 1,070.
Paper 1
Chemical Reactions
193 questions in the guide, across 14 subtopics. More from this topic
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Writing formulae of elements and compounds
What is the formula of carbon dioxide, and what does the subscript tell you?
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CO₂, where the subscript 2 shows that each molecule contains two oxygen atoms. -
Balanced equations, and deducing formulae from ions
Deduce the formula of sodium sulfate from the ions Na⁺ and SO₄²⁻.
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Na₂SO₄, because two sodium ions are needed to balance one sulfate ion. -
Conservation of mass, and changes of mass in open systems
4 g of hydrogen reacts completely with 32 g of oxygen. What mass of water is formed?
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36 g. -
Exothermic and endothermic reactions, and reaction profiles
Between which two points on a reaction profile is the activation energy measured?
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From the energy level of the reactants up to the top of the curve. -
Oxidation and reduction in terms of oxygen
In 2CuO + C → 2Cu + CO₂, state which substance is oxidised and which is reduced.
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Carbon is oxidised because it gains oxygen, and copper oxide is reduced because it loses oxygen.
Paper 1
Elements, Compounds and Mixtures
253 questions in the guide, across 17 subtopics. More from this topic
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Purity, and melting point data
A sample contains nothing but copper atoms. Is it an element, a compound or a mixture, and is it pure?
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It is an element, and it is pure because only one kind of atom is present. -
Formulations, and separating mixtures
Why do the proportions of the components in a formulation matter so much?
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Because the properties of the finished product depend on the proportions, so changing them gives a product that behaves differently. -
Interpreting chromatograms and Rf values
A substance has an Rf value of 0.60 and the solvent front moved 10.0 cm. How far did the spot move?
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It moved 6.0 cm, because 0.60 × 10.0 = 6.0. -
Metals and non-metals in the Periodic Table
How does a non-metal oxide behave when it dissolves in water?
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It is acidic and gives a solution with a pH below 7. -
Ionic, covalent and metallic bonding compared
Which types of substance contain covalent bonds?
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Simple molecular substances, giant covalent structures and polymers all contain covalent bonds.
Paper 2
Global Challenges
306 questions in the guide, across 19 subtopics. More from this topic
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Extracting metals by reduction and by electrolysis
Give a word equation for the reduction of iron(III) oxide by carbon.
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Iron(III) oxide + carbon → iron + carbon dioxide. -
Nitrogen, phosphorus and potassium in agriculture
What is meant by an NPK fertiliser?
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A fertiliser containing compounds that supply all three of nitrogen, phosphorus and potassium. -
Recycling, and the decisions behind it
Give one reason a recycled material is often used for a lower-grade purpose than the original product.
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Reprocessing can shorten polymer chains or leave impurities, so the material is weaker or less pure. -
Comparing glass, ceramics, polymers, composites and metals
Which is stronger for its mass, a carbon fibre composite or steel?
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The composite, because it has a comparable strength but a much lower density. -
Predicting the products of organic reactions
Which product is formed when hydrogen adds across the double bond of propene?
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Propane, C₃H₈.
Paper 2
Monitoring and Controlling Chemical Reactions
145 questions in the guide, across 9 subtopics. More from this topic
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Carrying out an acid–alkali titration
What is meant by the end point of a titration?
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It is the point at which the indicator changes colour permanently, showing that the two solutions have just reacted completely. -
Theoretical mass and percentage yield
How is the percentage yield of a reaction calculated?
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Divide the actual mass of product obtained by the theoretical mass and multiply by 100. -
Atom economy and its calculation
Under what circumstances does a reaction have an atom economy of 100%?
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When there is only one product, so every atom in the reactants ends up in the substance that is wanted. -
Measuring the rate of a reaction, and rate graphs
Give the units in which a rate of reaction is expressed when gas volume is measured, and when mass loss is measured.
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Gas volume gives a rate in cm³/s or cm³/min, and mass loss gives a rate in g/s or g/min. -
Factors affecting rate, and collision theory
Which of the factors that change rate applies only to reactions involving gases?
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Pressure, because only gases are compressed enough for pressure to change how closely the particles are packed.
Paper 1
Particles
60 questions in the guide, across 4 subtopics. More from this topic
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The particle model and changes of state
Name the change of state in which a liquid becomes a gas, and the reverse change.
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A liquid becoming a gas is boiling or evaporating, and a gas becoming a liquid is condensing. -
The particle model and changes of state
Explain why burning magnesium in air is a chemical change.
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The magnesium atoms join with oxygen atoms to form a new substance, magnesium oxide, which has different properties from the magnesium. -
How the atomic model changed, and the structure of the atom
Explain how Rutherford interpreted the results of the alpha scattering experiment.
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He concluded that an atom is mostly empty space with its positive charge and nearly all its mass concentrated in a tiny nucleus at the centre. -
How the atomic model changed, and the structure of the atom
How does the radius of the nucleus compare with the radius of the whole atom?
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The nucleus is very much smaller, with a radius of the order of ten thousand times less than that of the atom. -
The size of atoms, and the subatomic particles
Put a nucleus, a whole atom and a small molecule in order of increasing size.
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The nucleus is smallest, then the atom, then the small molecule.
Paper 2
Predicting and Identifying Reactions
113 questions in the guide, across 9 subtopics. More from this topic
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Groups 1, 7 and 0, and why they behave as they do
In what form do the elements of Group 7 exist?
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As diatomic molecules of two atoms sharing a pair of electrons, such as Cl₂ and Br₂. -
Transition metals
What colours are solutions containing copper(II) ions, iron(II) ions and iron(III) ions?
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Copper(II) solutions are blue, iron(II) solutions are pale green and iron(III) solutions are orange-brown. -
Predicting reactivity from the Periodic Table
Predict the formula of the compound formed between potassium and iodine.
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KI, because potassium loses one electron and iodine gains one. -
Reactivity of metals with water and acids
Compare how magnesium reacts with cold water and with steam.
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It reacts extremely slowly with cold water, but burns vigorously in steam to form magnesium oxide and hydrogen. -
Tests for oxygen, hydrogen, carbon dioxide and chlorine
Describe the test for chlorine and its positive result.
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Hold damp blue litmus paper in the gas; chlorine turns it red and then bleaches it white.
OCR GCSE Chemistry A, Foundation tier Active Recall Guide
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