Question

why heat is known as energy

Answer 1

Heat, energy that is transferred from one body to another as the result of a difference in temperature. If two bodies at different temperatures are brought together, energy is transferred—i.e., heat flows—from the hotter body to the colder. The effect of this transfer of energy usually, but not always, is an increase in the temperature of the colder body and a decrease in the temperature of the hotter body..

Therefore it is correct to state heat as a form of Energy

Answer 2

Every physical thing is energy in some way.. heat is a form of energy, rather than existing as a solid or any other material ..they exist as a matter transformed into the energy waves.. that's heat is all about