Free·GCSE Chemistry
Free GCSE Chemistry Questions and Answers
12 questions, one from each topic, with the answer that takes every mark and what it is worth. Nothing to sign up to and nothing to download — they are on this page.
Atomic structure and the Periodic Table, Structure, bonding and the properties of matter, Chemical changes, Energy changes in chemistry, Rates and equilibrium, Quantitative chemistry, Chemical analysis, Industry, organic chemistry and the atmosphere and Apparatus and working scientifically
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Describe how the model of the atom changed as a result of the alpha particle scattering experiment.
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The full-mark answer · 4 marks
The plum pudding model described a ball of positive charge with electrons embedded in it. Most alpha particles passed straight through the foil, showing that an atom is mostly empty space. A small number were deflected through large angles, showing a concentrated positive charge. A very few rebounded, showing that nearly all the mass is in that small volume. The model became a tiny, dense, positively charged nucleus surrounded by electrons.
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Explain why the noble gases in Group 0 are unreactive.
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The full-mark answer · 2 marks
Noble gas atoms have a full outer shell of electrons. Reacting involves losing, gaining or sharing outer electrons in order to obtain a full outer shell, and a noble gas already has one, so it has no tendency to react.
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Name the type of bonding in sodium chloride.
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The full-mark answer · 1 mark
Ionic bonding.
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Describe what happens to the particles in a solid as it melts.
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The full-mark answer · 3 marks
The particles gain energy and vibrate more strongly about their fixed positions. At the melting point they have enough energy to overcome the forces of attraction holding them in a fixed arrangement. They break free and can move past one another, though they stay close together.
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Give the state symbol used for a substance dissolved in water.
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The full-mark answer · 1 mark
(aq)
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Describe the test for hydrogen and the test for carbon dioxide.
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The full-mark answer · 4 marks
Hydrogen: hold a lighted splint at the mouth of the test tube; the gas burns with a squeaky pop. Carbon dioxide: bubble the gas through limewater; the limewater turns cloudy or milky.
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Explain what is meant by activation energy.
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The full-mark answer · 2 marks
The minimum energy that colliding particles must have in order to react. A collision with less than this energy will not result in a reaction.
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Name three factors that increase the rate of a chemical reaction.
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The full-mark answer · 3 marks
Increasing the temperature, increasing the concentration of a solution, and increasing the surface area of a solid.
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State the law of conservation of mass.
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The full-mark answer · 1 mark
The total mass of the products of a chemical reaction is equal to the total mass of the reactants.
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Give the meaning of the word pure as a chemist uses it.
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The full-mark answer · 2 marks
A pure substance is a single element or a single compound, not mixed with any other substance. In everyday use pure means that nothing has been added, so a mixture such as orange juice can be called pure while a chemist would not.
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Describe the basic principles of carrying out a life cycle assessment of a product.
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The full-mark answer · 4 marks
A life cycle assessment considers every stage of a product’s life: extracting and processing the raw materials; manufacturing and packaging; using the product over its lifetime; and disposing of it at the end of its life. Transport between the stages is included. At each stage the resources used, the energy required, the water used and the waste and pollutants produced are assessed.
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Describe how you would carry out a titration to find the volume of acid needed to neutralise 25.0 cm³ of alkali.
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The full-mark answer · 4 marks
Use a pipette to transfer 25.0 cm³ of the alkali into a conical flask and add a few drops of indicator. Fill the burette with the acid and record the initial reading. Add the acid slowly, swirling and adding dropwise near the end point, until the indicator changes colour permanently. Record the final reading and subtract to obtain the titre. Repeat until concordant titres are obtained.
What the book adds
These are the answers that score everything. GCSE Chemistry Questions & Answers is the other half: the same questions answered weakly, middlingly and strongly, the mark each version scores, what separates them, and the mark scheme behind it — a hundred questions across every topic, written for the teacher marking them rather than the pupil sitting them.