Capstone: Exo or endo?
One question runs through the whole of C5: does the change give out energy to the surroundings, or take it in? An exothermic change warms the surroundings up; an endothermic change cools them down. Sort each reaction or process into the right box.
Drag each one into a box — or tap it to step through the boxes. Then press Check.
Exothermicgives out energy · surroundings warm up
Endothermictakes in energy · surroundings cool down
📋 C5 Energy Changes — Quick-Reference Summary
- Exothermic: energy out to the surroundings, temperature up, products lower in energy (combustion, oxidation, neutralisation). Endothermic: energy in, temperature down, products higher in energy (thermal decomposition).
- Required practical: measure temperature change in a polystyrene cup with a lid; the cup insulates to reduce energy transfer.
- Displacement & data skills: displacement reactions are exothermic and a more reactive metal gives a bigger temperature rise; plot type of metal as a bar chart; uncertainty = ½ × range; a glass beaker instead of a polystyrene cup is a systematic error.
- Activation energy: the minimum energy needed to react. On a reaction profile it is reactants → peak; the overall energy change — the enthalpy change ΔH — is reactants → products (down/negative for exo, up/positive for endo).
- Bond energies H: breaking bonds is endothermic, making bonds is exothermic. Overall change = energy in (broken) − energy out (made); negative = exothermic.
- Cells T: two different metals in an electrolyte; bigger reactivity difference = bigger voltage. A battery is cells in series. Non-rechargeable reactions are not reversible.
- Fuel cells T: hydrogen + oxygen → water, producing electricity; evaluate against rechargeable batteries.
That completes C5. The reactions whose energy you have been measuring here — neutralisation, displacement, acid + metal and acid + carbonate — are the ones you met in C4 — Chemical Changes. The same idea of activation energy now leads straight into C6 — Rate & Extent of Chemical Change, where you will look at what controls how fast a reaction gives out or takes in that energy.