Question 49
Activity 3.2.1: The Mpemba effect. Investigate how the temperature of water affects the time taken to freeze. Use identical containers, water, measuring cylinder, heat source, thermometer, marker, timer and a freezer. If using plastic cups, keep water at or below 60 °C. Label cups with chosen starting temperatures, for example 10 °C, 20 °C and 30 °C. Add equal volumes of 10–20 cm³, place them in the freezer together and start timing. Check at equal intervals and record when ice forms across the surface. Assume the temperature inside the freezer is −18 °C. Calculate the temperature difference between −18 °C and the temperature of each sample of water that you used. Remember that you will be subtracting a negative number from a positive number. For example, 40 °C − (−18 °C) = 58 °C.
