Module 6 · Answers
Answers & explanations
Section A — Easy
01
Renewable: e.g. wind, solar, hydro, tidal, biomass. Non-renewable: coal, oil, natural gas, nuclear.
02
Energy can't be created or destroyed — it only moves from one store to another.
03
(a) Radiation (b) Conduction (c) Convection
04
power = energy ÷ time (P = E/t)
05
Temperature: how hot something is (°C) — based on average particle kinetic energy. Heat: total thermal energy in a substance — depends on temperature and amount.
Section B — Medium
06
180 000 J (180 kJ)
E = P × t = 1500 × 120 = 180 000.
07
1500 W (1.5 kW)
P = E ÷ t = 90 000 ÷ 60.
08
Metal is a good conductor — heat passes quickly into the food. Plastic is a poor conductor — the handle stays cool enough to hold safely.
09
Stretched: elastic store. Released: elastic store → kinetic store of the stone (it speeds up). Some energy is dissipated as thermal energy and sound.
10
Good: matt black surfaces emit infrared radiation more efficiently, so the radiator heats the room better.
Not so good: it also absorbs more dirt-coloured radiation in summer, can look unattractive, and shows dust more.
Not so good: it also absorbs more dirt-coloured radiation in summer, can look unattractive, and shows dust more.
Section C — Hard
11
(a) 10 kWh (b) £3.00
Energy = 2 × 5 = 10 kWh.
Cost = 10 × 30p = 300p = £3.00.
Cost = 10 × 30p = 300p = £3.00.
12
Gas: + reliable, can be turned on demand; − non-renewable, releases CO₂ and other pollutants.
Wind: + renewable, no CO₂ in operation; − unreliable (no wind = no electricity), can affect wildlife and views.
Wind: + renewable, no CO₂ in operation; − unreliable (no wind = no electricity), can affect wildlife and views.
13
A vacuum between the walls stops conduction and convection (no particles). The shiny silvered walls reflect infrared radiation back inside the flask. The stopper reduces convection out of the top. Together, all three types of heat transfer are minimised.
14
Each bounce, some energy is dissipated as sound and heat (from the squashed ball and air resistance). The remaining gravitational energy at the top of each bounce is less than before, so the ball rises lower. Energy isn't lost — it's just spread out into the surroundings.