Describe how energy changes from a usable form to a less usable form in a buildings heating system

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.

one negative thing it that it can kill water animals. another negative thing is it can cause the destruction of ecosystem. one way water pollution can be reduced is to conserve energy.