Question #8a949

1 Answer
Oct 10, 2015

Specific heat is all about energy needed to produce an increase in the temperature of a substance.


The specific heat of a substance tells you how much energy in the form of heat you must supply to increase the temperature of #"1 gram"# of that substance by #1^@"C"#.

Now, here's how you can think about this. For a given system, its internal energy consists of kinetic energy and potential energy.

When you're dealing with changes in temperature, you are actually dealing with the kinetic energy part of a system's internal energy.

Temperature is actually a measure of the average kinetic energy of the molecules or atoms that make up a system.

So when you're looking at the specific heat of a substance, you are actually looking at what amount of heat must be added to a unit of mass, let's say #"1 gram"#, of that substance so that the average kinetic energy of the molecules that make up that gram of substance , i.e. its temperature, increases by #1^@"C"#.

If you're looking at the specific heat values for two substances, then you can say that the substance with the smaller specific heat will require less energy per unit of mass to raise its temperature than the substance with the higher specific heat.

SImply put, the difference in specific heat values tells you how much more energy is needed to produce the same increase in temperature per unit of mass for two substances.

For example, liquid water has a specific heat at room temperature of #"4.184 J/g"""^@"C"#. By comparison, ethanol has a specific heat of #"2.46 J/g"""^@"C"#.

This tells you that you need to supply less heat to a sample of ethanol to increase its temperature by, let's say, #20^@"C"#, than you need to supply to an equivalent sample of water to get the same effect.

So, as a conclusion, for substances with higher specific heat values you need to supply more energy in the form of heat to cause the same increase in temperature than you would for an equivalent sample of a substance with a lower specific heat value.