The Law of Conservation of Energy
This simply states that energy cannot be created or destroyed, it can only be transferred from one form to another.
This may seem strange because there is talk of an energy crisis. If energy cannot be destroyed, how can there be a crisis?
The problem is that heat energy is dissipated, i.e. heat energy that is produced spreads out. The radiators in a lecture room produce heat energy. This heat energy dissipates and the surrounding area becomes very slightly warmer etc. This dissipated heat energy cannot be regained in a useful form.
A fuel releases energy when it undergoes a chemical reaction. Food is a fuel and when this is broken down in our bodies, during respiration, energy is released. Coal, oil and gas are fossil fuels and, as we shall see below are made up of biomass, so when they are burnt the energy that is released is dissipated. The energy is spread out and is lost to us in a useful form whilst at the same time contributing to global warming.
Coal, oil and gas are fossil fuels, which have been formed over the last 600 million years. Coal is the fossilised remains of huge forests which covered many parts of the world in prehistoric times and hence contains biomass. As the trees and plants died, they were covered in layers of silt and sand and, under great pressure, gradually became formed into coal deposits. In a similar way, oil comes from the remains of tiny creatures which lived in the prehistoric seas. Along with the oil deposits, gas frequently forms and collects in porous rocks.
More fossil fuels have been used in this century than in all the previous centuries put together. Our modern lifestyle in the Western World demands high energy usage. An average house may have a washing machine, a dishwasher, central heating, a tumble dryer, one or more televisions, a microwave, a computer etc. Compare this to the average house just thirty years ago! As the Third World becomes more developed, their energy consumption is also set to increase drastically.
There is obviously a limit to the supplies of fossil fuels and the reserves will one day run out - this is what is meant by the energy crisis.
Petrol is derived from oil and so is also a fossil fuel that will one day be used up. A car that has a low fuel consumption is not just cheaper to run, it is also more environmentally friendly.