Heat is a form of energy that flows from a hot body to a cold body, measured in Joules (J). Temperature measures the hotness or coldness of a body and is measured in Kelvin (K).
Example: when water is heated on a gas stove, heat transfers to the water, and its temperature rises to 100°C while boiling.
Heat
Heat is a form of energy that is transferred from a hotter body to a colder body due to a temperature difference. This transfer continues until both bodies reach thermal equilibrium. Heat is energy in transit; once transferred, it becomes internal energy in the body and is measured in joules (J).
When heat is supplied to a substance, it increases the internal energy of its molecules, which may raise its temperature or change its state (solid, liquid, or gas). Heat transfer occurs through conduction, convection, and radiation in different situations.
- The SI unit of heat is the joule (J).
- Heat can also be measured in calories (cal), where: 1 Cal = 4.186 J
Heat Transfer
Heat transfer is the process by which thermal energy moves from one body or region to another due to a temperature difference. Heat always flows from a body at higher temperature to a body at lower temperature until thermal equilibrium is reached.
Processes of Heat Transfer:
- Conduction: Transfer of heat through a solid without the actual movement of particles.
- Convection: Transfer of heat by the actual movement of fluid particles (liquids and gases).
- Radiation: Transfer of heat in the form of electromagnetic waves without any medium.
Temperature
Temperature is a measure of the degree of hotness or coldness of a body. It determines the direction of heat flow, i.e., heat always flows from a body at higher temperature to a body at lower temperature when they are in thermal contact.
It can also be defined as the thermal condition of a body which decides whether it will gain or lose heat energy. Since human touch gives only a qualitative idea of temperature, precise measurement is done using instruments called thermometers.
- The SI unit of temperature is Kelvin (K).
- Other commonly used units are degree Celsius (°C) and degree Fahrenheit (°F).
- The three main temperature scales are the Kelvin scale, Celsius scale, and Fahrenheit scale.
Measurement of Temperature
Temperature is measured indirectly because molecules are too small to observe their motion directly. When a substance is heated, the kinetic energy of its molecules increases, causing expansion in most materials. This expansion is used in thermometers as a basis for measuring temperature. Thus, thermometers measure temperature by using the physical change in a substance with heat.
Heat vs Temperature
Heat | Temperature |
|---|---|
| Heat is a from of energy transferred between two bodies due to a temperature difference. | Temperature is defined as the measure of the degree of hotness or coolness of any object. |
| Heat is the energy transferred from one body to another due to a temperature difference. | Temperature is the average kinetic energy of molecules in a substance. |
| Heat is a form of energy and has the capacity to do work | Temperature doesn't have a working capacity. |
| Heat can flow from a hot to a cold object. | Temperature can rise when heated and decreases when an object is cooled down. |
| The SI unit of Heat is Joule (J) and can also be measured in Calories (Cal). | SI unit of temperature is Kelvin (K). Other units of temperature are °C and °F. |
| Heat can be denoted by the symbol Q. | Temperature can be denoted by the symbol T. |
| The measure of Heat can be done with Calorimeter | Temperature is measured using a thermometer |