What is Heat (energy input)?

Heat is energy that moves from something warm to something cooler.

Imagine you're sitting on a sunny windowsill, your legs start to feel warm because the sunlight is giving them heat energy. Now think of your favorite chocolate bar: when it’s in your hand, it's cool, but after a few minutes, it starts to melt. That happens because your warm hands are passing their heat energy to the chocolate.

Heat can move in different ways:

• Like when you put your feet on the floor and feel them get warm: that’s conduction, where heat moves through touching.
• Like when you sit near a fire and feel the warmth even if you're not touching it: that’s radiation, like how sunlight warms your skin.
• Like when you blow on hot soup to cool it down: that’s convection, where heat moves with moving air or liquid.

Heat is just energy in motion, and it wants to go from warm places to cooler ones, just like you might want to move from a crowded room to an empty one!