Answer:
The warm exhaust from the natural gas heater
is the result of taking usable energy (in the
natural gas), using some of it, then releasing
the less usable form (exhaust). or you can write -> Electricity is a usable form of energy, but heat is not. Heat is simply dissipated to the surroundings as a result of temperature gradient. Thus, energy is transformed from usable to non-usable form.
