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 is degrees Celsius (°C) or Kelvin (K).

An example of a thermometric property is the thermal expansion of liquids, which is exemplified by the rise of mercury in a thermometer.

Heat is the form of energy that is transferred between systems or objects with different temperatures, flowing from the hotter object to the cooler one until thermal equilibrium is reached.

The three ways in which heat can be transferred are conduction, convection, and radiation.

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

The rise in temperature of the water can be calculated as follows:

$\Delta T = T_{final} - T_{initial} = 100 °C - 20 °C = 80 °C$.

Using the formula for heat:

$Q = mc\Delta T$,

where:

• m = 500 g (or 0.5 kg),
• c = 4200 J/kg·K (specific heat capacity of water),
• \Delta T = 80 °C,

we calculate:

$Q = 0.5 \times 4200 \times 80 = 168000 J.$

The power (energy per second) provided by the electric ring is given as 2 kW, which is equivalent to:

$Power = 2000 W = 2000 J/s.$

Using the formula for time:

$t = \frac{Q}{P},$

where:

• Q = 168000 J (energy required) and
• P = 2000 J/s (power supplied),

we find:

$t = \frac{168000}{2000} = 84 s.$