A cryogenic cooling unit contains 0.040 kg of liquid nitrogen at −206 ∘C-206\ ^{\circ}\text{C}−206 ∘C.
At atmospheric pressure, the transition temperature between liquid nitrogen and nitrogen gas is −196 ∘C-196\ ^{\circ}\text{C}−196 ∘C.
The specific heat capacity of liquid nitrogen is 2000 J/kg ∘C2000\ \text{J/kg}\ ^{\circ}\text{C}2000 J/kg ∘C.
The specific latent heat for the change between liquid and gas is 200 000 J/kg200\,000\ \text{J/kg}200000 J/kg.
Energy continues to be transferred to the nitrogen at −196 ∘C-196\ ^{\circ}\text{C}−196 ∘C until all the liquid has become gas.
Name this change of state.
Before its state begins to change, the liquid nitrogen reaches −196 ∘C-196\ ^{\circ}\text{C}−196 ∘C.
Calculate the energy absorbed by the nitrogen during this temperature rise.
Use the equation
ΔQ=m×c×Δθ\Delta Q = m \times c \times \Delta\thetaΔQ=m×c×Δθ
The nitrogen then remains at −196 ∘C-196\ ^{\circ}\text{C}−196 ∘C while the whole sample changes state.
Calculate the additional energy absorbed during this stage.
Use the equation
Q=m×LQ = m \times LQ=m×L
A component must transfer 8.5 kJ of energy to the nitrogen.
Explain whether this mass of nitrogen can absorb all this energy before any nitrogen gas becomes warmer than −196 ∘C-196\ ^{\circ}\text{C}−196 ∘C.
110 exam-style questions on Edexcel GCSE Physics 14.2 Specific heat capacity and latent heat, covering 14.2.1 Heating, temperature and changes of state, 14.2.2 Specific heat capacity and specific latent heat, 14.2.3 Specific heat capacity calculation, 14.2.4 Specific latent heat calculation, and 14.2.5 Reducing energy transfer through thermal insulation. Each one has a worked solution and a mark scheme showing where the marks go.