Next the heat gets transferred from water to metal spoon by conduction. Metal is a good conductor of heat so it gets hot easily. When the spoon gets heated, the spoon’s particles gain more energy and vibrate more vigorously. The particles bump into nearby particles and make them vibrate more. This is how heat passes energy from the hot end of the spoon to the cool end of the spoon. Here is particle diagram to show how it works-
As the water gets heat up, it changes to water vapour. This is where the evaporation takes place.
The reason why the wooden handle of the saucepan doesn’t get hot because the wood isn’t a good conductor of heat. This is why because the particles in the wooden handle are bound together strongly; they are unable to move very fast, so the handle will never become as hot as the metal spoon.
Conduction, convection and radiation
Thermal energy can be transferred by:
Conduction
Convection
Radiation
Conduction
When a substance is heated, its particles gain energy and vibrate more vigorously. The particles bump into nearby particles and make them vibrate more. This passes the thermal energy through the substance by conduction, from the hot end to the cold end. Substances that allow thermal energy to move easily through them are called conductors. Metals are good conductors of thermal energy. Substances that do not allow thermal energy to move through them easily are called insulators. Air and plastics are insulators.
Convection
The particles in liquids and gases can move from place to place. Convection happens when particles with a lot of thermal energy in a liquid or gas move, and take the place of particles with less thermal energy. Thermal energy is transferred from hot places to cold places by convection.
Radiation
All objects transfer thermal energy by infrared radiation. The hotter an object is, the more infrared radiation it gives off.
No particles are involved in radiation, unlike conduction and convection. This means that thermal energy transfer by radiation can even work in space, but conduction and convection cannot.
Radiation is how we can feel the heat of the Sun, even though it is millions of kilometres away in space. Infrared cameras give images even in the dark, because they are detecting heat, not visible light.
