Conduction is the transfer of thermal energy with no overall transfer of matter. Conduction occurs within a material or between materials that are touching. Conduction in gases are slower than in liquids and solids because the particles in a gas collide less often. In most solids, conduction occurs as particles vibrate in place and push on each other. Conduction is faster in metals than in other solids because metals have free electrons that transfer thermal energy.
When a ball is pulled back and released, you might think that all of the balls would move but instead the ball on the other end moves. Most kinetic energy is transferred to one ball on the end. Conduction is the transfer thermal energy, without transferring of matter.
Convection is the transfer of thermal energy when particles of a fluid move from one place to another.
When air at the bottom of the oven, it expands and becomes less dense than the surrounding air. Hot air rises, due to the difference in density. The rising air cools as it moves away from the heat source. Air circulating in an oven is convection current. A convection current occurs when a fluid circulates in a loop as it alternately heats up and cools down.
Radiation is the transfer of energy by waves moving through space. All objects radiate energy. As an object's temperature increases, the rate at which it radiates energy increase.
The heating coil on a stove radiates so much energy that it glows. If you are close to the heating coil, you absorb radiation, which increases your thermal energy. it warms you up! The farther away you are, the less radiation you receive, and the less it warms you.
Thermodynamics are the study of conversions between thermal energy and other forms of energy. Energy cannot be created or destroyed, but it can be converted into different forms. Thermal energy flows spontaneously from hotter objects to colder ones. Thermal energy that is not converted into work is called waste head.
First Law of Thermodynamics
Energy cannot be created or destroyed, but energy can be converted into different forms. The first law of thermodynamics states that energy is conserved. If energy is not added to a system, it can increase the thermal energy of the system or do work on the system. No matter what happens, all energy added to the system can be accounted for.
Second Law of Thermodynamics
The second law of thermodynamics states that thermal energy can flow from colder objects to hotter objects only if work is done on the system.
A refrigerator must do work to transfer thermal energy from the cold food compartment to the warm room air. The thermal energy is released by coils at the bottom or in the back of the refrigerator.
Third Law of Thermodynamics
The third law of thermodynamics states that absolute zero cannot be reached. Scientists have been able to cool matter almost all the way to absolute zero. The scientists were just 3 billionths of a kelvin above absolute zero!