Here’s something we tend to take for granted: drop a few ice cubes into a glass of water at room temperature, and in a few minutes the water will cool.
How does this work?
Heat is a measure of molecular activity: the faster a thing’s molecules move, the more heat that substance contains.
And because everything is made of molecules, and molecules are in constant motion, everything contains at least some heat.
As we know, ice is colder than room temperature water.
Because ice molecules move slowly and cluster tightly together, they produce a relatively low amount of heat.
When ice is placed in a glass of water whose molecules are moving at a greater rate, the ice begins to absorb energy,
because heat always travels from regions of relative warmth to colder areas in order to equalize temperatures.