Heat is a kind of energy that can move from place to place. One important rule about heat is that it always travels from warmer things to cooler things. Heat never flows the other way on its own.

Think about holding an ice cream cone on a hot day. Your hand is warmer than the ice cream, so heat flows from your warm hand into the cold ice cream. That is why ice cream melts in your hand and drips everywhere.

The same thing happens with a warm cup of cocoa. The cocoa is hotter than the air and your hands, so heat leaves the cocoa and moves into the cooler air around it. Little by little, the cocoa cools down until it is the same warmth as the room.

Heat keeps moving until both things are the same temperature. When a warm object and a cool object touch, the warm one cools down and the cool one warms up until they finally match. Then the heat stops flowing.

We use the flow of heat every day. A warm blanket traps your body heat to keep you cozy, and a cold drink cools your hand because heat flows from your hand into the drink. A pot on the stove heats up because heat flows from the hot burner into the pot.

People also slow down the flow of heat on purpose. A lunchbox cooler keeps snacks cold by blocking heat from getting in, and oven mitts stop the stove's heat from reaching your hands. Knowing how heat flows helps us stay warm, stay cool, and stay safe.