A cup of hot water is sealed inside a perfectly insulated box. The water cools until it is at the same temperature as the air in the box. Which statement about the box is correct?
the total energy in the box has decreased, because the water has cooled
the total energy in the box has increased, because the air has warmed up
the total energy in the box is unchanged, because it is a closed system
the total energy in the box is now zero, because no energy can enter it
40 exam-style questions on AQA GCSE Physics 1.2 Conservation and dissipation of energy, covering 1.2.1 Energy transfers in a system and 1.2.2 Efficiency. Each one has a worked solution and a mark scheme showing where the marks go.