Temperature

Temperature is the physical property of a system which underlies the common notions of "hot" and "cold"; the material with the higher temperature is said to be hotter. Temperature is a measure of the average kinetic energy of the particles in a sample of matter. In other words, temperature is a measure of activity and the frequency of collisions of molecules.

Overview

The formal properties of temperature are studied in thermodynamics. Formally, temperature is that property which governs the transfer of thermal energy, or heat, between one system and another. When two systems are at the same temperature, they are in thermal equilibrium and no heat transfer will occur. When a temperature difference does exist, heat will tend to move from the higher-temperature system to the lower-temperature system, until thermal equilibrium is established. This heat transfer may occur via conduction, convection or radiation (see heat for additional discussion of the various mechanisms of heat transfer).

Related Topics:
Thermodynamics - Heat - Thermal equilibrium - Conduction - Convection - Radiation

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Temperature is related to the amount of thermal energy or heat in a system. As more heat is added the temperature rises, similarly a decrease in temperature corresponds to a loss of heat from the system. On the microscopic scale this heat corresponds to the random motion of atoms and molecules in the system. Thus, an increase in temperature corresponds in an increase in the rate of movement of the atoms in the system.

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Temperature is an intensive property of a system, meaning that it does not depend on the system size or the amount of material in the system. Other intensive properties include pressure and density. By contrast, mass and volume are extensive properties, and depend on the amount of material in the system.

Related Topics:
Intensive property - Pressure - Density - Mass - Volume - Extensive properties

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Applications

Temperature plays an important role in almost all fields of science, including physics, chemistry, and biology.

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Many physical properties of materials including the phase (solid, liquid, gaseous or plasma), density, solubility, vapor pressure, and electrical conductivity depend on the temperature. Temperature also plays an important role in determining the rate and extent to which chemical reactions occur. This is one reason why the human body has several elaborate mechanisms for maintaining the temperature at 37 °C, since temperatures only a few degrees higher can result in harmful reactions with serious consequences. Temperature also controls the type and quantity of thermal radiation emitted from a surface. One application of this effect is the incandescent light bulb, in which a tungsten filament is electrically heated to a temperature at which significant quantities of visible light are emitted.

Related Topics:
Phase - Solid - Liquid - Gas - Plasma - Density - Solubility - Vapor pressure - Electrical conductivity - Chemical reaction - Thermal radiation - Incandescent light bulb - Tungsten - Electrically - Light

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Temperature-dependence of the speed of sound in air c, density of air ρ and acoustic impedance Z vs. temperature °C

Related Topics:
Speed of sound - Acoustic impedance

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