A cryogenic containment system contains liquid nitrogen at its boiling point of 77 K. Due to a small vacuum breach, thermal energy enters the system at a constant rate of 45 W. If it takes exactly 3.0 hours3.0\text{ hours}3.0 hours for all of the liquid nitrogen to completely vaporise into gas at 77 K, what is the mass of the nitrogen that was in the system?
(Specific latent heat of vaporisation of nitrogen, Lv=2.0×105 J kg−1L_v = 2.0 \times 10^5\text{ J kg}^{-1}Lv=2.0×105 J kg−1)
2.4 kg2.4\text{ kg}2.4 kg
4.1×10−2 kg4.1 \times 10^{-2}\text{ kg}4.1×10−2 kg
6.8×10−4 kg6.8 \times 10^{-4}\text{ kg}6.8×10−4 kg
0.41 kg0.41\text{ kg}0.41 kg
27 exam-style questions on OCR GCSE Physics Changes of state. Each one has a worked solution and a mark scheme showing where the marks go.