Translations of Encyclopedia about Physics

Temperature

If we want to describe the state of some substance, we must also mention its temperature. Temperature measures the amount of heat, where heat is understood as the kinetic (moving) energy of atoms and molecules. The following law applies here: the greater the kinetic energy of its particles, the higher the temperature of a substance.

The most important units for measuring heat are Celsius (°C) and kelvin (K), which is how we measure temperature as well. Each of these methods of measuring temperature require at least two fixed and relational values. For example, Celsius uses the temperature at which water (at sea level) freezes and at which it boils. Under certain conditions, water always boils at 100°C and freezes at 0°C.

Kelvin is based on an absolute zero value where all particles come to a rest (their kinetic energy is zero). This is measured as 0 K (zero kelvin) and corresponds roughly to -273.15°C, a temperature which science has not yet managed to reproduce.

When measuring temperature, we must be aware that atmospheric pressure and pressure in general affects the quantity of standard values. For example, the atmospheric pressure on Mount Everest is different then on sea level and, on Mount Everest, water boils at a different temperature than 100°C.

If we place two object with different temperatures next to one another, their mutual temperature becomes balanced, where the kinetic energy from the warmer object transfers over to the cooler object, something which can be observed in our daily life. For example, if we put some clothing on a radiator, the temperature of the clothing will increase while the temperature of the radiator decreases. This law applies also during the heating of a house, where a radiator passes its heat to the cooler air around it, which then circulates around the house and heats it up. The griddle of an electric cooker works in the same way, where it transfers its heat to a kettle, which in turn transfers its heat the contents within it.

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