The temperature of an object is measured using a thermometer, which is based on the variation of its thermometric property - Leaving Cert Physics - Question 7 - 2008

The unit of temperature in the SI system is the Kelvin (K), but degrees Celsius (°C) is also commonly used.

An example of a thermometric property is the resistance of a thermistor, which changes with temperature.

Heat is a form of energy that is transferred between two objects due to a temperature difference. It flows from the hotter object to the cooler one.

1. Conduction: the transfer of heat through direct contact between materials.
2. Convection: the transfer of heat through the movement of fluids (liquids or gases).
3. Radiation: the transfer of heat in the form of electromagnetic waves.

Specific heat capacity is defined as the amount of heat energy required to raise the temperature of 1 kg of a material by 1 Kelvin (or 1 °C). The formula is given by: $c = \frac{Q}{m \Delta T}$ where $c$ is the specific heat capacity, $Q$ is the heat added, $m$ is the mass, and $\, \Delta T$ is the change in temperature.

The rise in temperature can be calculated as: $\Delta T = 100 °C - 20 °C = 80 °C$

Using the formula: $Q = mc\Delta T$ Substituting the values:

• Mass ($m$) = 0.5 kg
• Specific heat capacity ($c$) = 4200 J/kg·K
• Change in temperature ($\Delta T$) = 80 °C We get: $Q = 0.5 \times 4200 \times 80 = 168000 J$

Power ($P$) is given as 2 kW, which can be converted to watts (1 kW = 1000 W): $P = 2 \text{ kW} = 2000 \, W$

The time can be calculated using: $t = \frac{Q}{P}$ Substituting the values:

• $Q = 168000 \, J$
• $P = 2000 \, W$ We get: $t = \frac{168000}{2000} = 84 \, s$