Describe what happens when two substances at different temperatures come into contact. describe how the law of conservation of energy applies to this system.

When two substances at different tempeartures como into contact, the substance that is at higher temperature will transfer energy, in the form of heat, to the substance that is at lower temperature, until their temperatures get equal.

In this case, if the two substances are isolated of the rest of the universe, the law of conservation of energy states tha the heat released by the substance initially at higher temperature is the same amount of heat gained by the substance originally at lower temperature.