Specific heat capacity

The specific heat capacity is the heat energy needed to raise the temperature of 1 g of a substance by 1 °C. Malay: muatan haba tentu · Chinese: 比热容.

It is the letter c in the heat equation Q = mcθ. A substance with a high specific heat capacity needs a lot of heat to warm up, while one with a low value warms quickly for the same heat supplied. In this chapter you almost always work with aqueous solutions, and the specific heat capacity of the solution is taken to be that of water, the value printed in the question, in units of J g⁻¹ °C⁻¹.

Example. In a neutralisation experiment the solution behaves like water, so you use the specific heat capacity given, together with the mass of solution and the temperature change, in Q = mcθ. Because c already has the units J g⁻¹ °C⁻¹, mass must be in grams and the temperature change in °C for the answer to come out in joules.

Confusion to avoid. Do not confuse specific heat capacity with heat capacity. Specific heat capacity is per gram of substance and is a fixed property of the material; heat capacity is for a whole object and depends on how much of it there is. In Q = mcθ it is always the specific (per-gram) value that multiplies the mass.

Knowing what c stands for keeps the units of Q = mcθ consistent, which is why SPM Chemistry supplies the specific heat capacity in the question rather than expecting you to recall it. The high value for water is the reason water makes a good medium for absorbing the heat of a reaction without its temperature shooting up too far, and the reason a dilute solution can be assumed to behave like water. When you answer, copy the value of c exactly as the question gives it, make sure the mass is in grams and the temperature change in °C, and the result will come out in joules with no further unit conversion needed.