These twelve entries cover the word pairs that cause slips across the three sciences. Each gives the plain meaning, an example, and the term it is most often confused with. The English, BM and Chinese concept bridge lets you look up terms in your own language and link them to lessons.
Use your syllabus wording when you write definitions in an exam. The plain meanings below are for understanding.
Double award vs two separate subjects
Plain meaning: a double award is one course reported as a double qualification. Example: you study one course for 0654, not two separate syllabuses. Confused with: taking two separate tuition subjects. Read the two-grade structure to see why that difference matters.
Core vs Extended tier
Plain meaning: tiers are entry routes with different question ranges, where your course offers them. Example: your centre enters you for one tier, and questions follow that tier. Confused with: year group or difficulty preference. See checking tier details with your centre.
Diffusion vs osmosis
Plain meaning: diffusion is the net movement of particles from a higher to a lower concentration. Osmosis is the net movement of water through a partially permeable membrane, from a more dilute to a more concentrated solution. Example: a potato strip placed in salt solution loses water by osmosis. Confused with: each other, because both go “down a gradient”. See transport and gas exchange.
Respiration vs breathing
Plain meaning: respiration is the chemical process in cells that releases energy from food. Breathing moves air in and out of the lungs. Example: a runner breathes faster so that cells can respire faster. Confused with: each other, in written answers. Practise in the integrated biology module.
Element, compound and mixture
Plain meaning: an element has one type of atom, a compound has different atoms chemically bonded, and a mixture is substances not chemically bonded. Example: oxygen is an element, water is a compound, air is a mixture. Confused with: mixture and compound. See bonding and properties.
Mole vs mass
Plain meaning: mass is how much matter there is, in grams. A mole is an amount of substance, found as mass ÷ relative formula mass. Example: 18 g of water is 1 mol, since its relative formula mass is 18. Confused with: using grams where moles are needed. Practise in the integrated chemistry module.
Concentration in g/dm³ vs mol/dm³
Plain meaning: both measure how much solute is in one dm³, in different units. Example: 4.0 g of a solute with relative formula mass 40, dissolved to make 250 cm³ of solution, is 16 g/dm³ (4.0 ÷ 0.250) and 0.40 mol/dm³ (16 ÷ 40). Confused with: each other, and with cm³ versus dm³. See carrying units across tasks.
Heat vs temperature
Plain meaning: heat is energy transferred because of a temperature difference. Temperature shows how hot an object is. Example: a bucket of water at 40 °C holds more thermal energy than a teaspoon of water at 60 °C. Confused with: each other. See the integrated physics module.
Mass vs weight
Plain meaning: mass is the amount of matter, in kg. Weight is the gravitational force on it, in newtons. Example: a 3.0 kg bag with g = 10 N/kg has weight 30 N. Confused with: using kilograms for a force. See combining energy and motion.
Speed vs velocity
Plain meaning: speed has size only. Velocity has size and direction. Example: a runner on a circular track at constant speed has changing velocity, because direction keeps changing. Confused with: each other. Practise in the numerical fluency module.
Independent, dependent and control variables
Plain meaning: you change the independent variable, measure the dependent variable, and keep the control variables the same. Example: in a test of salt concentration and potato mass, concentration is independent, mass change is dependent, and strip size and time are controls. Confused with: mixing up the first two. See separating a hypothesis from a measurement plan.
Accuracy vs precision
Plain meaning: accuracy is closeness to the true value. Precision is how close repeated readings are to each other. Example: readings of 6.1, 6.2 and 6.1 for a true value of 5.0 are precise but not accurate. Confused with: each other. Revisit them in the experimental evaluation module.
Which pairs should you start with?
Start with the two you just recognised as yours. Write one sentence for each word, then a second sentence that uses both. After that, check whether your mistake log, described in revising from actual gaps, shows the same pair.
If these pairs keep returning under time pressure, our teachers work through them live in online one-to-one Co-ordinated Sciences tuition.