A student carried out an experiment to determine the specific heat capacity of water. Figure 12 shows the equipment the student used to heat the water.

Why did the student insulate the beaker of water?

In this experiment, a heater transfers electrical energy into thermal energy. The aim is to measure how much energy is required to raise the temperature of a known mass of water by a certain amount. A major source of error is that not all the thermal energy from the heater goes into the water. Some of it will be transferred to the beaker itself, and a significant amount can be lost to the cooler surrounding air through conduction, convection, and radiation. By insulating the beaker (e.g., with a layer of foam or cotton wool), the rate of this heat loss is significantly reduced. This ensures that most of the energy measured by the joulemeter is actually used to heat the water, leading to a more accurate result for the specific heat capacity.