# What is Specific Heat Capacity

Specific heat capacity, also known as specific heat is the measure of heat or thermal energy that is required to heat a specific unit quantity of a given substance by a given amount usually one degree.  This will tell you how much heat energy is required to say boil a cup of water.  Specific heat will therefore also tell you how much heat a substance can be used to store.  This specific heat capacity value is useful in engineering and building design.

The most commonly used carrier of heat is water (for example in heating systems) and for that reason I will use it as an example.  Water also has one of the better fluid specific heat capacities and has the advantage of being readily available most places.

In metric terms the heat required to raise the temperature of 1 kilogram or litre of water stored at 20 degrees Celsius by 1 degree is approximately 4183 joules.  This equates to a specific heat capacity of water of 4.183 kilojoules per kilo per degree Kelvin.

Be aware the specific heat capacity changes slightly as it heats up and cools down and completely changes when a substance changes state for example water boiled into steam.  Also the pressure of a substance will effect the specific heat capacity, for example water under pressure has a higher specific heat capacity.

In imperial terms the British Thermal unit (BTU’s for short) for example is a measure of the amount of heat it takes to raises the temperature of 1-pound of water by 1 degree Fahrenheit, this is of course similar in nature to the metric equation.  This is also I believe the unit commonly used in America.

Celsius and Kelvin

A degree in both Celsius and Kelvin is the same amount of temperature.  The varying factor is where the scale starts.  Celsius deals with the freezing point and boiling point of water for example 0 degrees centigrade is freezing point this equates to 273 degrees Kelvin.  Boiling point is 100 degrees Celsius, which equates to 373 degrees Kelvin.

Degree Kelvin starts from the theoretical point of absolute zero, this is the point where a substance is said to have no heat energy at all.  It is said to be impossible to actually obtain though temperatures close to it have been achieved.  Absolute zero would be 0 degrees Kelvin which would equate to –273 degrees Celsius.

Specific heat capacity can be a confusing subject due to the constant fluctuation of the factors involved. I hope this has given you some insight into it however.