A2 Daily A Level Physics question
Two 0.10 kg samples at the same initial temperature are heated in the lab by identical 50 W immersion heaters for exactly 2 minutes with no energy losses. One is aluminium (c ≈ 900 J kg−1 K−1) and the other is water (c ≈ 4200 J kg−1 K−1). Which statement must be true about their temperature rises?
Answer
The correct answer is D.
Correct: D — The aluminium’s temperature rise is about five times that of the water. For the same energy input and mass, temperature rise is inversely proportional to specific heat capacity, so ΔT_Al/ΔT_Water ≈ 4200/900 ≈ 4.7 ≈ five. A The higher specific heat of water means it needs more energy per degree, so for equal energy it warms less, not more. B Equal energy does not imply equal temperature rises because ΔT depends on mass and specific heat; here c differs greatly. C The ratio is not about two; using the values gives roughly 4.7, so twice is a significant underestimate. D Using the proportionality with the given c values gives a ratio close to five, matching this statement.