It depends on the kind of wood and the moisture content of the firewood.
Seasoned wood of beech equals 192 US gallon heating oil or 24727790 BTU or 27610 US.cu.ft. of natural gas.
You can easily calculate other energy amounts of wood at the Related Link.
Approx. 4-5 kWh/kg; see the link below for different types of wood.
how chemical energy produce in firewood useful
biomass
you use chemical energy by cooking an egg, burning wood, water on wood/metal
Burning charcoal, wood and coal.
It is termed to be combustion. Or carbon emission. Burning wood releases the carbon that was stored in the wood.
During burning (oxidation) the heat of combustion is released.
how chemical energy produce in firewood useful
LPG undergoes complete combustion on burning and produces high amount of energy, but not wood
'HEAT' energy
Energy cannot be created. (Or destroyed) Burning changes the chemical energy of the wood to heat energy and light energy.
Stored Chemical energy being converted to, and released as Heat energy.
when the wood burns, chemical reactions occur that change chemical potential energy into thermal energy and light enery. Well, the released energy just simply turns into thermal and light enery.
Thermal energy........
Fuels such as oil, wood, coal, and natural gas have energy stored in them. This kind of energy is called chemical process of burning, the energy is released in the form of heat.
By burning it. The heat it lets off will be energy.
People have been burning wood for centuries to provide themselves with heat energy.
Since the "law of conservation of energy" states that energy cannot be created or destroyed, all energy is never really destroyed only changed. Chemical energy is converted into thermal energy by certain chemical reactions, like combustion (when something is burned) or when fat is metabolized into heat for the body for example.