1. A fuel is any substance burned to supply energy. Most of the energy used today come from the burning of fossil fuels, such as natural gas, coal and oil.

2. Natural gas, coal and oil are called fossil fuels because they are derived from the remains of ancient dead plants and animals. Over hundreds of millions of years, decay, pressure and heat converted dead plants and animals into fossil fuels. Even though these processes are still going on today, these processes are very slow. We are using fossil fuels at a rate that far exceeds the ability of nature to create these fuels. Someday we may run out of fossil fuels. Because of this, fossil fuels are considered a nonrenewable resource.

3. The fuels used for heating are:

a. natural gas--mostly methane with some ethane and propane. Natural gas is a clean burning fuel which releases carbon dioxide, water and very few impurities. Natural gas is efficient. It produces more heat per unit than other fossil fuels.

b. coal--is composed of carbon and hydrocarbons. It is only one half as efficient as natural gas, so that per unit amount, twice as much coal must be burned to produce the same amount of heat as is produced by one unit of natural gas. Coal also contain impurities which pollute the environment. The burning of coal releases carbon dioxide, water and sulfur dioxide. Sulfur dioxide combines with moisture in the air to produce sulfuric acid. The sulfuric acid falls as acid rain damaging plants, animals and poisoning lakes, streams and rivers. There are filters which remove the sulfur and other pollutants from coal emissions. The advantage of coal is that it is more plentiful than natural gas.

4. Coal and natural gas can be used to produce heat without having to refine them. However, crude oil must be refined to be used as fuel. Crude oil is a mixture of hydrocarbons, which must be separated to be useful as fuels. These hydrocarbons are separated by a process known as fractional distillation. In fractional distillation, heat is applied to crude oil. The hydrocarbons with the lowest boiling point are vaporized first and are captured in a devise called a still. Then the heat is raised to vaporize and capture the hydrocarbons with the second lowest boiling point. As you raise the heat, one-by-one the different hydrocarbons are vaporized and captured.

5. The heavier, long chain hydrocarbons, are not as useful as the lighter hydrocarbons. So these heavy hydrocarbons are changed into lighter hydrocarbons by a process known as cracking. Cracking is done by using a catalyst; therefore the plant which does this is often called a cat. cracker. Cracking is the process of changing heavy hydrocarbons into lighter hydrocarbons.

6. Light hydrocarbons such as propane and butane can be cooled so that these gases are condensed into liquids. They are then bottled and sold as bottled gas.

7. Gasoline is heavier than propane and butane. It is composed of 25 hydrocarbons, but gasoline is mostly heptane and octane. If you add up all the hydrocarbons which compose gasoline and divide it by the number of hydrocarbons, the average is octane.

8. When gasoline is burned in an automobile engine it must be mixed with air before burning. The devise which does this on some cars is called a carburetor. When automobile engines burn gasoline, they release exhaust which includes:

a. carbon dioxide, carbon monoxide and water

b. unburned hydrocarbons

c. nitrogen oxide (79% of air is nitrogen)--(a source of acid rain)

d. sulfur oxide--( a source of acid rain)

e. lead (in countries such as Mexico which still use leaded gasoline)

9. By law, most automobile exhaust systems in the U.S.A. contain a catalytic converter. This catalytic converter is designed to trap and remove many of these exhaust pollutants. However, leaded gasoline will destroy the catalytic converter and cannot be used in cars which have a catalytic converter. The catalyst in this converter is platinum. This is why these converters are expensive. 10. Complete burning--when a hydrocarbon is burned in the presence of plenty of oxygen. In complete burning, the primary products of combustion are carbon dioxide and water.

11. Incomplete burning--when a hydrocarbon is burned with limited oxygen. In incomplete burning, the products of combustion are carbon dioxide, water, carbon monoxide, and soot.

12. Hydrocarbons should always be vaporized to encourage more complete burning. Vaporization increases the surface area of the fuel so that it can be exposed to plenty of oxygen. This is why you should always have a clean and functional air filter on an automobile engine.

13. Acid rain comes from:

a. sulfuric acid from sulfur impurities contained in many hydrocarbons which are burned as fuel.

b. nitric acid--produced by the fact that air is 79% nitrogen. The nitrogen oxide which converts to nitric acid is a primary reason for smog in large cities.

14. All hydrocarbon fuels burn incomplete to some degree. Even methane, which is the most complete, contains some impurities which form pollution.

15. Theoretically, hydrogen gas would burn completely producing no pollution. It is the cleanest burning fuel. However, there would be problems in having tanks to contain a large volume of hydrogen gas. There would also be problems with storage and transportation.

Storage and transportation would pose problems as hydrogen is explosive.

Fuels Study Sheet