Answer, and give a reason. Why does a lake in winter take so long to freeze over completely? …

Step 1. (a) Every kilogram of water must give out $3.34 \times 10^{5}\ \text{J}$ to freeze, and the ice on top slows the loss of heat.

Step 2. (b) As the water on the fruit freezes it gives out its latent heat, which keeps the fruit near $0\ ^\circ\text{C}$ instead of colder.

Step 3. (c) The ice must take in its latent heat to melt before it warms at all: far more than cold water can take in.