Q. Determine the heat transfer?

Ans. Let's say a blacksmith tosses a hot horse shoe into a bucket of water. The horseshoe will get cooler while the water gets hotter. Ideally, the amount of heat gained by the water is equal to the amount of heat lost by the horseshoe. Of course some of the heat will be lost to the atmosphere but we can usually ignore this as long as the items in question are reasonably well insulated.

A little note about insulation:

When doing experiments with heat transfer and energy exchange, it is important to isolate the experiment from the atmosphere. Otherwise the energy might be exchanged with the atmosphere giving incorrect results. We can use a special instrument called a calorimeter to insulate our experiment and make careful measurements.