1Temperature
Temperature tells you how hot something is, in degrees Celsius (°C). The hotter something is, the faster its particles move.
temperature
Lesson 15.2 notes
Conduction and thermal equilibrium
Temperature, hot to cold, thermal equilibrium, temperature and energy, conduction, conductors and insulators.
2Hot to cold
When a hot object touches a cold one, energy is transferred from the hotter one to the cooler one until they reach the same temperature: thermal equilibrium.
thermal equilibrium
3Cooling down
A hot drink cools until it reaches room temperature. It cools fastest at first, when the difference between its temperature and the room's is biggest.
4Temperature isn't energy
A bath at 40 °C stores far more thermal energy than a cup of tea at 80 °C, because it has so much more water. Temperature and energy are different things.
5Conduction
In conduction, particles at the hot end vibrate more and bump into their neighbours, passing energy along. It works best in solids, where the particles are close together.
conduction
6Metals conduct best
Metals are the best conductors: as well as vibrating particles, they have free electrons that carry energy quickly. Copper conducts better than steel; glass and wood are poor.
conductorfree electrons
7Insulators
Poor conductors are insulators: wood, plastic, wool and air. A pan has a metal base to conduct energy into the food and a plastic handle that stays cool.
insulator
Explore: Thermal equilibrium lab
Set the temperatures of two blocks and put them together. Watch the energy flow until they reach the same temperature.
Common mistake: Cold does not flow
When you hold an ice cube, cold doesn't flow into your hand. Energy flows out of your hand into the ice, because your hand is warmer. Energy always moves from hotter to cooler.
Remember
- Energy moves from a hotter object to a cooler one until they reach the same temperature: thermal equilibrium.
- Conduction: vibrating particles pass energy to their neighbours. It works best in solids, especially metals.
- Insulators, such as wood, plastic and trapped air, conduct energy very slowly.
Going further at GCSE