For instance, it would take 2 minutes to heat an electric kettle holding about 1.6 kg of water from 200C to 600C while it will take 100 minutes to heat a hot water tank holding about 160 kg of water by the same temperature with a 5 kW immersion heater.
This explains why it takes longer waiting for hot water tanks to heat up water for bathing than would be the time waited for kettles to boil. The water contained in hot water tanks have higher heat capacities that the water in kettles. Hence, it would require more energy to raise the temperature of the water in the hot water tank than it would be required to raise the temperature in the kettle.
Taking the same mass of different materials, it would take different times to raise their temperatures by equal magnitude using the same electric heater. Thus, Avison (2009) documents various heat capacities for 1 kg of different materials as shown in Figure 1.
Measuring the heat capacity of a substance with reference to its specific mass gives its specific heat capacity. Hewitt et al. (2012) define specific heat capacity, c, as the heat energy required to raise the temperature of a kilogram of a substance by 1 Kelvin. Hence:
Note that experimental values tend to be higher than the exact specific heat capacities of various substances because of the heat losses during heating (Avison, 2009). Due to such difficulties in determining the specific heat capacities of substances, they have been documented for referencing. Table 1 shows some specific heat capacities for various substances.
The knowledge of heat capacity, and specific heat capacity by extension, informs on the heating characteristics of substances. As such, it plays a critical role in determining the substances to use when making instruments where the heating characteristics of such substances are of basic importance. Therefore, substances that have a small specific heat capacity heat up quickly and additionally