Energy and temperature
Teaching Guidance for 11-14
Temperature depends on energy and mass
Wrong Track: If you warm both things up for the same time, the temperature goes up by the same amount.
Right Lines: If you warm two objects (of the same substance) up for the same time (same amount of energy shifted to each thermal store), the temperature rise depends on the mass of the objects. The same quantity of energy, shared out amongst less mass, gives a bigger temperature rise.
Highlighting the distinction
Thinking about the learning
Pupils often have difficulties recognising the difference between temperature and energy. Temperature is an intensive quantity that does not depend on the mass of material that you have. Energy is an extensive quantity that does depend on the amount of matter involved. The easiest way to picture the difference between the temperature and energy of an object is in terms of a particles model:
- The temperature of an object depends on the state of motion of its particles: the higher the temperature, the faster moving are the particles (the number of particles does not matter).
- The amount of energy in the thermal store of an object is related to the state of motion of its particles and the number of particles: more energy involves a larger number of faster moving particles.
Thinking about the teaching
You can helpfully draw attention to the difference between energy and temperature by considering objects with two different masses of the same substance at the same temperature:
'Suppose I run myself a nice, deep, hot bath. I take a plastic cup and scoop some water from the bath. What can you say about the temperature of the water in the bath compared to the temperature of the water in the mug? Yes! It's the same temperature. What can you say about the amount of energy in the thermal store of the bath water compared with the thermal store of the mug? Yes! There is much more energy stored in the bath of water. Just imagine all of those particles moving around. They have the same average speed as the particles in the mug, but there are so many more of them moving about.'