Question

Which of the following is not a fossil fuel?
A. Mineral coal
B. Wood
C. Petroleum
D. Natural gas

Answer 1

Hint: A fossil fuel is a fuel formed by natural processes, such as anaerobic decomposition of buried dead organisms, containing organic molecules that release energy upon combustion.

Complete answer:
‘Wood' is not a fossil fuel.
- Fossil fuels consist of carbon in a very large amount. They include petroleum, coal, and natural gas. Sometimes, Peat is also considered as a fossil fuel.
- Fossil fuels are of great use to us because they can be burnt to (oxidized to carbon dioxide and water) produce a large amount of energy.
- Organic material can only be said as a fossil fuel if it is buried and changed by heat and pressure. Coal, gas, and oil are considered as fossil fuels because their chemical nature was gradually altered over time.
- Unlike coal or crude oil, wood is not a product of decomposition of organic matter and therefore it is not fossil fuel - it is only fuel.
- Coal is slowly formed in layers by the dead and decaying plants and animals under the sedimentary rocks. It takes hundreds of years for coal to form.
- Oil originally is not liquid but a solid material. It is formed between layers of sedimentary rock, like shale. This solid material is heated in order to extract the thick oil that can be used to make gasoline and other products.
- Natural gas is generally found in crevices above oil deposits in the sedimentary rocks. It can also be found in rock layers that do not contain oil.

Note:
- Fossil fuels are non-renewable resources of energy.
- Methane is the most important constituent of natural gas.
- The burning of fossil fuels by humans is the largest source of emissions of carbon dioxide, which is one of the greenhouse gases that cause global warming.