GCSE-readyInternational GCSE Science (Double Award): common mistakes
The wrong answers students pick most often in our Science (Double Award) questions, and why they are wrong. Read these before a test, then open the lesson for anything that surprises you.
Getting started
- Getting started: particles and dissolving
- Not “Salt”. Salt is the solute: the substance that dissolves.
- Not “Salt water”. Salt water is the solution.
- Not “Liquid particles do not move”. Liquid particles do move; diffusion happens in liquids, just more slowly.
- Getting started: atoms, elements, compounds and formulae
- Not “Fluorine”. Fluorine is F.
- Not “O2”. O2 has only oxygen atoms, so it is an element.
- Not “He”. Helium is an element.
- Getting started: forces, mass and weight
- Not “There are no forces acting”. Weight still acts; it is balanced by air resistance.
- Not “Kilogram (kg)”. The kilogram is the unit of mass.
- Not “Joule (J)”. The joule is the unit of energy.
- Getting started: cells and the light microscope
- Not “Cytoplasm”. The cytoplasm is where reactions happen, but it does not hold the genetic material.
- Not “Cell membrane”. The membrane controls what enters and leaves, not the cell's activities.
- Not “Vacuole”. The vacuole holds cell sap.
- Getting started: life processes, photosynthesis and respiration
- Not “Carbon dioxide and water”. These are the reactants, not the products.
- Not “Glucose and carbon dioxide”. Carbon dioxide is used up, not made.
- Not “Oxygen and water”. Water is a reactant in photosynthesis.
Biology: 1 The nature and variety of living organisms
- Characteristics and groups of living things
- Not “Excretion”. All organisms excrete waste.
- Not “Respiration”. All organisms respire.
- Not “Reproduction”. All organisms reproduce.
Biology: 2(a) to (d) Cells, biological molecules and movement of substances
- Levels of organisation and cell structure
- Not “A chloroplast”. A chloroplast is an organelle.
- Not “A palisade cell”. This is a single cell.
- Not “Muscle tissue”. This is a tissue.
- Animal, plant and bacterial cells
- Not “Ribosomes”. Ribosomes make proteins.
- Not “Nucleus”. The nucleus holds the genetic material.
- Not “Cell wall”. The cell wall strengthens plant cells.
- Enzymes
- Not “The enzyme is killed”. Enzymes are molecules. They are not alive, so they cannot be killed.
- Not “The substrate is used up”. The substrate is still there. It just no longer fits.
- Not “The enzyme moves too fast”. Faster movement speeds reactions up until the shape changes.
- Investigating enzymes: temperature and pH
- Not “The temperature”. Temperature is the independent variable.
- Not “The time taken”. Time is the dependent variable.
Biology: 2(e) to (f) Nutrition and respiration
- Leaf structure, minerals and starch tests
- Not “Nitrate”. Lack of nitrate causes stunted growth, often with yellow older leaves. This plant is growing normally, so magnesium (needed for chlorophyll) is the better answer.
- The human digestive system
- Not “Storing faeces”. Faeces are stored in the rectum.
Biology: 2(g) to (h) Gas exchange and transport
- Blood and the immune response
- Not “Oxygen bound to haemoglobin”. Oxyhaemoglobin is inside red blood cells.
Biology: 2(i) to (j) Excretion, co-ordination and response
- Excretion in plants and humans
- Not “Removal of undigested food”. That is egestion.
- Homeostasis and temperature control
- Not “They move deeper into the skin”. Blood vessels do not move. The arterioles narrow.
- The nervous system and reflexes
- Not “Motor neurone”. Motor neurones carry impulses away from the CNS to effectors.
- Not “Relay neurone”. Relay neurones are inside the CNS.
- Not “Effector neurone”. There is no such neurone. Effectors are muscles or glands.
Biology: 3(b) Inheritance
- Inheritance and Punnett squares
- Not “The alleles an organism has”. That is the genotype.
- Family pedigrees and probability
- Not “1 : 2 : 1”. 1 : 2 : 1 is the ratio of genotypes, not phenotypes.
- Mitosis and the cell cycle
- Not “Prophase”. In prophase the chromosomes condense and the nuclear membrane breaks down.
- Not “Anaphase”. In anaphase the chromatids are pulled apart.
- Not “Telophase”. In telophase new nuclei form.
- Meiosis and reproduction
- Not “It only needs one parent”. Needing only one parent is an advantage of asexual reproduction.
- Not “It is faster than asexual reproduction”. Asexual reproduction is usually faster.
- Not “Offspring are identical to the parent”. Identical offspring come from asexual reproduction.
Biology: 4 Ecology and the environment
- Air pollution and the greenhouse effect
- Not “Nitrous oxide”. Nitrous oxide is a greenhouse gas.
Chemistry: 1(a) to (b) States of matter, and elements, compounds and mixtures
- Elements, compounds and mixtures
- Not “Oxygen”. Oxygen is an element.
- Not “Air”. Air is a mixture.
- Not “Sea water”. Sea water is a mixture.
Chemistry: 1(c) to (d) Atomic structure and the Periodic Table
- Atomic structure
- Not “Atoms with different numbers of protons”. Changing the number of protons changes the element.
- Atoms, molecules and relative atomic mass
- Not “He”. Helium exists as single atoms.
Chemistry: 1(f) to (i) Bonding, structure and electrolysis
- Ionic, covalent and metallic bonding
- Not “Diamond”. Diamond is giant covalent.
- Not “Magnesium oxide”. Magnesium oxide is ionic.
- Not “Copper”. Copper is metallic.
- Ions, ionic formulae and ionic lattices
- Not “NH3”. NH3 is ammonia, a molecule.
- Not “NO3−”. That is nitrate.
- Not “NH4−”. The ammonium ion is positive.
- Covalent molecules and their properties
- Not “Larger molecules have more covalent bonds to break when boiling”. Boiling does not break covalent bonds.
Chemistry: 2(f) to (h) Acids, bases, salts and chemical tests
- Neutralisation and salts
- Not “It turns limewater milky”. That is the test for carbon dioxide.
- Not “It relights a glowing splint”. That is the test for oxygen.
- Not “It bleaches damp litmus paper”. That is the test for chlorine.
Physics: 1 Forces and motion
- Units, prefixes and vectors
- Not “Newton”. The newton is the unit of force, including weight.
- Acceleration and velocity-time graphs
- Not “Distance”. Distance is the area under a velocity-time graph.
Physics: 3 Waves
- Wave properties
- Not “The distance between two crests”. That is the wavelength.
- Not “The number of waves per second”. That is the frequency.
Physics: 7 Radioactivity and particles
- Dangers of radiation and radioactive waste
- Not “Food is sterilised with gamma rays”. This is irradiation; the food does not become radioactive.