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.

the old alchemists made significant contributions to science even though there starting premises were off a bit. their conclusions after failure would steer them into better directions for investigation. science is no more than close observation and the initial mistakes result in rethinking and retrying experiments.