One bench, three sciences.
A rate graph that switches between a chemistry clock, pondweed and a radioactive source, a heating curve with real plateaus, and a displacement grid you have to predict before you reveal.
One graph, three sciences
FIG. 01 · RATE · C6 · B4 · P4The disappearing-cross clock: time how long until you cannot see the X through the flask.
Pondweed in a beaker, counting oxygen bubbles. Move the lamp and the whole graph tells you what is holding it back.
Enzymes: faster up to about 40 °C, then they denature and it collapses.
Decay is random, so we only ever quote a half-life — the time for half of the nuclei left to decay.
Why it is marked: combined science asks the same question in three costumes — what is the rate, and what is limiting it? In chemistry the rate is 1 ÷ time; in biology the graph levels off because something other than light has taken over; in physics the count rate halves in equal steps no matter where you start. Same graph skills, three papers.
Where the energy actually goes
FIG. 02 · PARTICLE MODEL · P3 · C2water · c(ice) 2100 · c(water) 4180 · c(steam) 2000 J kg⁻¹ °C⁻¹ · Lf 334 · Lv 2260 kJ kg⁻¹
Energy supplied = power × time. Nothing is lost to the room in this model.
Why it is marked: during the flat sections the energy is still going in, but the temperature does not rise — it is being used to break the forces between particles, not to speed them up. That is latent heat, and the boiling plateau is far longer than the melting one because pulling molecules completely apart costs about seven times more than loosening them.
Predict, then reveal
FIG. 03 · CHEMICAL CHANGES · C4Metal (row) added to salt solution (column) · click a cell to test it
Mg > Zn > Fe > Cu
A metal only displaces a metal below it. Anything else and you get no reaction at all — no fizzing, no colour change, nothing.
Why it is marked: displacement is competition for electrons. The more reactive metal is oxidised — it loses electrons and goes into solution — while the less reactive metal ion is reduced back to the metal and drops out as a solid. Getting OIL RIG the right way round on a displacement reaction is the single most common higher-tier slip.