Temperature – a measure of the movements (vibration) of the molecules inside a thing. If the thing has a high temperature, it means the average speed of its molecules is fast. A thing may have a high temperature but because it contains very few or light atoms it has very little heat.
- Celcius – sometimes called centigrade, is a unit of measurement used in many countries to measure temperature. 0 degrees (°) Celsius is the melting point of pure water at sea level (normal pressure). 100° Celsius is the boiling point of water at normal pressure. (Water boils at a lower temperature at higher altitudes). 1 °C is therefore one hundredth (the 100th part) of that difference. The Celsius scale, based on multiples of ten, is used with SI, or metric measurements.
- Fahrenheit – a unit of measurement used to measure temperature. The conversion rate to Celsius is C= 5/9 x (F − 32). The degree Fahrenheit is abbreviated °F.
- Kelvin – a base SI unit of measurement, defined as the fraction 1/273.16 of the temperature of the triple point of water, which is the temperature at which water in solid, liquid, and gaseous state coexist in equilibrium. By writing temperatures in kelvins one does not need to use negative numbers.
- absolute zero – The coldest possible temperature is called absolute zero and is equal to -273.15 degrees Celsius, or zero kelvin (0 K). In theory, absolute zero is the temperature where the particles of matter stop moving. Absolute zero is impossible to achieve, because all particles move, even if it is just a small vibration.
Heat is not the same as temperature. Heat is energy which moves from one thing, cooling it, to another, heating it.
- heat capacity – The amount of heat that is needed to make a substance one degree higher is called its heat capacity. Different substances have different heat capacities. For example, a kilogram of water has more heat capacity than a kilogram of steel. This means that more energy is needed to make the temperature of water 1 °C hotter than is needed to make the temperature of steel 1 °C hotter.
- cold molecules – a recently discovered process for cooling large organic molecules to less than 0.1 K using a technique that should also work with proteins and other biomolecules. Temperatures this low will allow scientists to study molecular structures and chemical processes with unprecedented precision
- temperature – Scientifically, temperature is a physical quantity which describes how quickly molecules are moving inside a material. In solids and liquids the molecules are vibrating around a fixed point in the substance, but in gases they are in free flight and bouncing off each other as they travel. In a gas the temperature, pressure and volume of the gas are closely related by a law of physics.