During an experiment to measure the specific latent heat of vaporisation of water, cold water was placed in an insulated copper calorimeter - Leaving Cert Physics - Question 2 - 2015

The steam was dried by passing it through a drying agent, typically sodium sulfate or glass wool, before entering the calorimeter. This helps remove any excess moisture, ensuring that only dry steam enters the calorimeter.

In addition to the mass measurements, the following should be recorded:

• Initial temperature of the water: To determine the starting point for heat calculations.
• Final temperature of the mixture: After the steam has condensed and transferred heat to the water.
• Steam temperature: To verify that the steam is at its boiling point.

To calculate the mass of the steam used, subtract the mass of the calorimeter and water from the total mass after the steam has been added:

$\text{Mass of steam} = \text{(Mass of calorimeter + water + steam)} - \text{(Mass of calorimeter + water)}$

Thus,

$\text{Mass of steam} = 92.3 \text{ g} - 90.7 \text{ g} = 1.6 \text{ g}$.

The latent heat released can be calculated using the formula:

$Q = m \cdot L$

where:

• $Q$ = latent heat released
• $m$ = mass of steam in kilograms
• $L$ = specific latent heat of vaporisation

First, convert the mass of steam from grams to kilograms:

$m = 1.6 \text{ g} = 0.0016 \text{ kg}$

Now substitute the values into the equation:

$Q = 0.0016 \text{ kg} \cdot 2.3 \times 10^6 \text{ J kg}^{-1}$

Calculating this gives:

$Q = 3680 \text{ J}$

One essential safety precaution is to wear gloves to protect your hands from potential hot surfaces or steam burns during the experiment. Additionally, safety goggles should be worn to protect the eyes from any splashes.