Ice cream is made by cooling a mixture of liquid ingredients until they freeze - AQA - GCSE Physics Combined Science - Question 5 - 2020 - Paper 1

As the liquid is cooled and begins to freeze, the kinetic energy of the particles decreases because they move less as they approach a solid state. The potential energy, however, decreases as the particles are arranged into a more stable and ordered structure.

Metal has a high thermal conductivity which allows energy to be transferred quickly from the mixture to the coolant, thus enabling the mixture to freeze more efficiently. In contrast, plastic has a low thermal conductivity which reduces heat transfer from the surroundings, helping to maintain the low temperature of the liquid coolant.

The liquid coolant should have a high specific heat capacity so it can absorb a large amount of energy without experiencing a significant temperature change. This property ensures that the coolant remains effective over a longer period.

Using the energy transfer equation, we have:

$165000 ext{ J} = m imes 3500 ext{ J/kg °C} imes (20 - (-1.5))$

This simplifies to:

$165000 = m imes 3500 imes 21.5$

From which:

$m = \frac{165000}{3500 imes 21.5} \approx 0.50 ext{ kg}$

Therefore, the mass of the mixture is 0.50 kg.