Question

(a) What happens when carbon burns in air? Write the chemical equation of the reaction that takes place.
(b) Why are coal and petroleum called fossil fuels?
(c) Explain how coal was formed on the earth.
(d) Describe how petroleum was formed on the earth.
(e) Name a fossil fuel other than coal and petroleum.

Answer 1

Hint: The remains of the historic animals and plants are termed as fossils. The natural form or source of energy that is used as fuels and formed from the decomposition of fossils are called fossil fuels. These fuels take millions of years to form on earth as a result of various chemical and physical changes.

Complete answer:
(a)The burning of carbon in air is a combustion reaction that results in the formation of carbon dioxide, heat and light, therefore it is an exothermic reaction as heat is released. The chemical equation is:
$C+{{O}_{2}}\to C{{O}_{2}}+heat+light$
(b)Coal and petroleum are called fossil fuels as they are a result of the decomposition of the dead remains of plants and animals that are termed as fossils, these when subjected to changes like weathering gets converted to fuels like coal and petroleum, hence the term fossil fuels.
(c) Coal is a form of carbon. It was formed millions of years ago by the decomposition of the plants and trees. The phenomena like volcano eruption and earthquakes resulted in the burial of the woods from plants and trees that got under the earth. This was subjected to high temperatures and pressures that made them into coal.
(d) Petroleum is a form of oil. It is formed due to the decomposition of the plants and animals in the sea. The dead bodies of aquatic and other animals and plants sank into the sea bed that decomposed and changed chemically due to high pressure, heat and the action of bacteria and got converted into petroleum. These changes happened in the absence of air and oxygen. The petroleum that was formed was trapped in non – porous rock layers.
(e) A fossil fuel other than petroleum and coal is natural gas.

Note:
The formation of these fossil fuels takes millions of years; therefore they should be used at a slower pace. These are termed as non – renewable resources, as they take millions of years to renew and once depleted we cannot make them for our use. While renewable resources are wind, solar energy, water sources etc.