In a classic experiment demonstrating the first law of thermodynamics, a paddle wheel is rotated inside a well-insulated container of liquid by a falling weight, causing the temperature of the liquid to rise.
What fundamental conclusion can be drawn from this observation?
Temperature is a physical store of energy.
The liquid absorbs heat from the cooler surroundings.
Mechanical work done on a system can increase its internal energy.
Energy is not conserved in this process.
533 exam-style questions on CIE IGCSE Physics 1.7 Energy, work and power, covering 1.7.1a Energy stores and energy transfers, 1.7.1b Conservation of energy, 1.7.1c Kinetic and gravitational potential energy, 1.7.2 Work done, 1.7.3 Energy resources, 1.7.3a Energy resources and electricity generation, 1.7.3b Nuclear fusion as an energy source, 1.7.3c Efficiency of energy transfer, and 1.7.4 Power. Each one has a worked solution and a mark scheme showing where the marks go.