When two objects at different temperatures touch, heat energy transfers from the hotter object to the colder object until they reach thermal equilibrium. This process is governed by the laws of thermodynamics, specifically the zeroth law of thermodynamics, which states that two objects in thermal equilibrium with a third object are also in thermal equilibrium with each other.

Here's a breakdown of what happens:

1. Temperature Difference: The initial temperature difference between the two objects creates a thermal gradient.

2. Heat Transfer: Heat energy naturally flows from areas of higher temperature to areas of lower temperature. This can occur through three mechanisms:

* Conduction: Heat transfer through direct contact between molecules. For example, when you hold a hot cup of coffee, your hand gets warm because of conduction.

* Convection: Heat transfer through the movement of fluids (liquids or gases). For example, a hot air balloon rises because the heated air is less dense and rises, carrying heat with it.

* Radiation: Heat transfer through electromagnetic waves. For example, the sun warms the Earth through radiation.

3. Thermal Equilibrium: The heat transfer continues until the two objects reach the same temperature. This state is known as thermal equilibrium. At this point, there is no further net transfer of heat energy between the objects.

Factors Affecting Heat Transfer:

* Temperature difference: The greater the temperature difference, the faster the heat transfer.

* Surface area: Larger surface area increases the rate of heat transfer.

* Material properties: Different materials conduct heat at different rates (e.g., metal conducts heat better than wood).

* Time: The longer the objects are in contact, the more heat is transferred.

Example:

Imagine putting a cold piece of metal into a hot cup of coffee. The heat from the coffee will flow into the metal until the metal and the coffee are at the same temperature. The metal will become warmer, and the coffee will become slightly cooler.