How GCSE Chemistry is assessed
Chemistry is taken either as a separate GCSE or as the chemistry part of combined science, and the exact papers, tiers and timings depend on the board and on what your school entered you for. Ask your teacher which specification you are on, then read its assessment section for the details that apply to you. These are the official pages for the main boards:
- AQA GCSE Chemistry (8462). AQA lists eight required practicals for this specification.
- Edexcel GCSE Sciences (2016). Pearson gives first assessment as 2018.
- OCR Chemistry A (Gateway Science) and OCR Chemistry B (Twenty First Century Science).
Whichever board you are on, treat the specification as your checklist. Every topic you are expected to know is listed there, and tiering decisions (Foundation or Higher) are made by your school.
Mistakes that quietly cost marks
Units
Write the unit on every numerical answer and check it is the one the question asks for. Mass in grams, volume in cm³ or dm³, concentration in g/dm³ or mol/dm³. Converting cm³ to dm³ means dividing by 1,000, and forgetting that is one of the most common slips in quantitative questions.
Balancing
Balance by changing the big numbers in front of formulae, never the small numbers inside them. Count each element on both sides at the end, including oxygen in compounds. A symbol equation that does not balance has not finished.
Significant figures
Keep the full calculator value until the last step, then round to the number of significant figures the question asks for, or to an appropriate number for the data, which is usually the fewest significant figures in the values you were given. Rounding halfway through pushes the final digit off.
Reading the question
Underline the command word before you write anything. Describe asks what happens, explain asks why, and evaluate asks you to weigh both sides and reach a judgement. A short answer that does the right job earns more than a long one that answers a different question. In calculation questions, check the mark allocation: several marks usually mean several steps are expected.
A four-week plan
Four to five short study blocks a week is enough to cover this. Fit it around your own timetable, which you can build with the free revision timetable.
- Week 1: foundations. Atomic structure and the periodic table, bonding, and a first pass at moles and balancing. Make a one-page sheet of formulae and definitions.
- Week 2: reactions. Chemical changes, energy changes and rates. Practise calculations from a blank page each time.
- Week 3: carbon and testing. Organic chemistry, chemical analysis, the atmosphere and resources, then the required practicals.
- Week 4: whole papers. Attempt past-paper questions under time, mark them against the mark scheme, and go back to whatever lost marks. Use the past-paper tool to log what you attempted.
If a week runs short, carry the unfinished topic forward instead of rushing it. Finish each study block by writing down the one thing you got wrong, so your next block starts there. If a topic keeps going wrong, that is a good thing to bring to a tutor, or ask your teacher, with the exact question in hand.
Technique by area
Atomic structure and the periodic table
Be fluent with protons, neutrons and electrons from a symbol, and with electron configurations for the first twenty elements. Explain group trends using the outer electron and its distance from the nucleus.
Bonding
Say which particles are involved, then link the bonding to the property: ionic compounds conduct when molten or dissolved because ions can move; simple molecular substances have weak forces between molecules, so low melting points. Draw dot-and-cross diagrams with care over the outer shell.
Quantitative chemistry
Set out calculations in steps: relative formula mass, moles, ratio from the equation, then the answer. Show each line so a slip can still earn method marks.
Chemical changes
Learn the reactivity series with its reasons, the acid reaction patterns (acid + metal, + carbonate, + base) and what happens at each electrode in electrolysis. Name the ions present before predicting products.
Energy changes
Distinguish bond breaking (energy taken in) from bond making (energy given out). Sketch a reaction profile and label reactants, products, activation energy and the overall change.
Rates of reaction
Explain changes using collisions: how often particles collide and how many collisions have enough energy. Practise reading a rate from the gradient of a graph.
Organic chemistry
Know the first four alkanes and alkenes by name and formula, the bromine water test, and the purpose of cracking. Draw displayed formulae with every bond shown.
Chemical analysis
Learn each test as a set of three parts: what you do, what you see, what it shows. For chromatography, calculate the Rf value as the distance moved by the substance divided by the distance moved by the solvent, measuring both from the start line.
h3>/h3>Keep the explanation of greenhouse gases and the changes in the atmosphere's composition in your own words, and link human activity to specific gases rather than writing in general terms.
Using resources
Be ready to describe how potable water is produced from fresh and salt water, and to weigh up advantages and disadvantages in life-cycle questions.
Required practicals
For each one, know the method, the variables you control, the hazards and how you would reduce an error. Questions often change the context, so practise applying the reasoning rather than recalling a single set-up.
Where to practise next
Try the GCSE Chemistry quiz and the glossary, build cards with the flashcard tool, and use the calculators for checking arithmetic.
Part of the GCSE Chemistry revision set: the glossary of key terms and self-marking quiz.