A student measured the temperature of a large bath full of water and a small cup full of water and said "they are both at the same temperature, so they must contain the same amount of energy" - Leaving Cert Physics - Question 8 - 2019

A thermometric property is a physical property of a substance that changes in a predictable way with temperature. This change can be measured and used to determine the temperature of the substance.

Another example of a thermometric property could be electrical resistance, as it varies with temperature.

Specific heat capacity is defined as the amount of heat energy required to raise the temperature of 1 kg of a substance by 1 K or 1 °C. It is expressed in joules per kilogram per Kelvin (J/kg·K).

The material in the bricks needs to have a high specific heat capacity so that it can absorb and store a significant amount of heat energy without experiencing a large change in temperature. This property is beneficial for maintaining a stable heat in the storage heater, allowing it to provide consistent warmth over time.

The heat energy gained by the water can be calculated using the formula:

$Q = mc heta$
where:

• $Q$ is the heat energy gained,
• $m$ is the mass of the water (1.5 kg),
• $c$ is the specific heat capacity of water (4200 J/kg·K),
• $heta$ is the change in temperature (88 °C - 15 °C = 73 °C).

Substituting the values into the equation:

$Q = 1.5 ext{ kg} imes 4200 ext{ J/kg·K} imes 73 ext{ K}$

Calculating:
$Q = 1.5 imes 4200 imes 73 = 461,100 ext{ J}$

So, the heat energy gained by the water is 461,100 joules.

Apart from boiling, one other change of state that can happen to water is melting, where ice (solid water) melts into liquid water.

Latent heat is defined as the amount of heat energy that is absorbed or released by a substance during a change of state at constant temperature. This energy change does not result in a change in temperature; it is used to alter the internal structure of the substance.