Apparatus

Fig 2 - the large (40 liter) tank was used so that the melting ice did not lower the temperature of the surrounding water significantly.  

Tap water temperature was adjusted from 4°C to 24°C by adding ice and by adding hot water. The ice cubes were all of approximately 20 grams and the same shape (cubic). The ice was weighed by placing it in a polystyrene cup to prevent water from affecting the balance.