Heat always moves from the hotter objects to
the colder one. Whenever there is a transfer
difference between two objects, the heat
energy will be transferred from the warmer
object to the cooler one until both objects
stabilize at the same temperature.
This is known as the law of heat transfer,
and is the basis of air conditioning operation.
When a hot cup of coffee is set aside for
some time, it becomes cold. Heat moves out
of the hot (90 C) coffee into the cooler (25 C)
surrounding air. In time the coffee will reach
the temperature of the surrounding air