Inside every object or substance are tiny particles (molecules). These particles are always moving. In cooler substances, the particles are moving slowly. In hotter substances, the particles move much faster.
The particles inside an ice cube are moving very slowly.
The particles in boiling water are moving very fast.
more movement of particles = more thermal energy
Remember the pot of boiling water? How did the water get so hot? First, it's important to know that thermal energy is transferred when two objects touch each other. Here's how it worked for the water:
Thermal energy always moves from hotter objects to cooler objects. Looking at the diagram below you should notice that the object in the middle is at a higher temperature than the two objects on the side. The arrows show the direction thermal energy would flow if these objects were placed in contact with each other.
The orange and yellow arrows in the diagram represent thermal energy. So when one object conducts thermal energy to another, we call that heat. Heat is not the energy itself, but the transfer. Thermal energy is transferred in three ways:
Many objects in your house emit thermal energy. The toaster you use for breakfast emits thermal heat to gently toast your bread. The coffee maker also uses thermal energy to make your parents their morning cup of coffee. Many scientists are now focusing on the uses "geothermal" energy, which uses natural heat of the earth to heat and cool homes and businesses. Computers use a vast amount of power in today's age, and many businesses in the future might need to use "geothermal" energy to power and cool their server hosting or other computing efforts.