Temperature is the degree of hotness or coldness of an object. When we talk about something feeling hot (like the soup we drink when were sick) or cold (like the snow, especially if youre not wearing gloves), were talking about temperature.

The temperature of an object, usually measured in degrees-Fahrenheit or degrees-Celsius, tells us how much heat, or energy, the object has. A boiling cup of water has very active molecules moving around very quickly and producing the heat we feel on our hands and faces. Colder objects dont have as much energy. Their molecules are much less active.

Think about this: If you put an oven mitt on a hot dish fresh from the stove, the oven mitt usually picks up some of the heat, right? This is one of the main ideas of thermodynamics, which studies (partly) how energy and heat work hand-in-hand. If there isnt any heat being transferred between two objects, those objects are the same temperature. But if one object is hotter, heat will flow naturally from the hotter object to the colder object; this is why the oven mitt gets warm.

Scientists usually use water to compare temperatures of things because its pretty easy to remember the boiling point and freezing point of good-old H2O: Water boils at 100 degrees Celsius and freezes at zero degrees Celsius. Its a little harder to remember the Fahrenheit scale, but water boils at 212 degrees Fahrenheit and freezes at 32 degrees Fahrenheit.

The Celsius scale is used in most of the world, except for Belize, Myanmar, Liberia and the United States. Scientists use the Kelvin scale, which doesnt measure temperature in degrees. Zero Kelvin is also called absolute zero, the coldest temperature and lowest energy level. Absolute zero is equal to about minus-273 degrees Celsius.

Ice gathers on a thermometer.
absolute zero

hypothetical coldest possible temperature where all molecular motion stops (-273.16 degrees Celsius and -459.69 degrees Fahrenheit). Also called zero Kelvin.

Celsius scale

scale for measuring surface temperature, used by most of the world, in which the boiling point of water is 100 degrees.


area of land that receives no more than 25 centimeters (10 inches) of precipitation a year.


capacity to do work.

Fahrenheit scale

scale for measuring surface temperature used by Belize, Liberia, Myanmar, and the United States.

freezing point

temperature at which liquid becomes solid; the freezing point of water is 0 degrees Celsius (32 degrees Fahrenheit).

Kelvin scale

scale for measuring temperature where zero Kelvin is absolute zero, the absence of all energy.


padded glove.


smallest physical unit of a substance, consisting of two or more atoms linked together.

research station

structure or structures built for scientific study of the surrounding region, possibly including residential and lab facilities.


degree of hotness or coldness measured by a thermometer with a numerical scale.


the study of the relationship between heat and mechanical energy, or work.