energy. In solids, for example, the atoms vibrate about their equilibrium positions; the stronger
these vibrations, the higher the temperature of the solid. A certain amount of heat supplied to a
large number of particles would not increase their average energy by much; however, if there were
only a small number of particles in the system, that same amount of heat is now spread not as
thinly, and thus each particle would gain a larger amount of energy, bringing up the temperature
more.
BASIC CONCEPT
The more of a substance there is, the more heat is required to bring about a change in its
temperature.Yet not every substance is responsive to heat to the same degree. Even though we expect from the
last paragraph that to raise 2 kg of a substance by 1°C requires more heat than raising 1 kg of the
same substance by 1°C (in fact, it requires twice the amount of heat), we would not expect that the
same amount of heat is required to raise the temperature of 1 kg of steel versus 1 kg of plastic. The
specific heat, c, is a proportionality constant that gives an indication of the ease with which one can
raise the temperature of something: the larger it is, the larger the amount of heat required to raise
its temperature a certain number of degrees, and also the more heat released if it cools by a certain
number of degrees. Its value is a property of the nature of the substance and does not change based
on the amount of stuff we have (that has already been taken into account by the mass). The specific
heat is often more formally defined as the heat necessary to raise the temperature of 1 kg or 1 g of a
material by 1°C or 1 K. Iron, for example, has a specific heat of about 0.1 kcal/kg°C, while water has a
specific heat of 1.0 kcal/kg°C. It is therefore much easier to raise the temperature of 1 kg of iron by
10°C than it is to do the same to 1 kg of water. In fact, you should be able to see that ten times the
heat is needed.
The mass and the specific heat are sometimes lumped together to give a quantity known as the heat
capacity. This quantity then describes the heat needed to raise the temperature of the object as a
whole by 1°C or 1 K.
While heat is associated with exchange of thermal energy, and we have so far been talking about the
mathematical relationship between heat and temperature changes, a system that is heated does
not necessarily increase in temperature. Heat can also increase the potential (rather than kinetic)