3.32. Hydrocarbons http://www.ck12.org
nonpolar, which means that their molecules do not have oppositely charged sides. Therefore, they do not dissolve in
water, which is a polar compound. In fact, hydrocarbons tend to repel water. That’s why they are used in floor wax
and similar products.
Classes of Hydrocarbons
Hydrocarbons are placed in two different classes: saturated hydrocarbons and unsaturated hydrocarbons. This
classification is based on the number of bonds between carbon atoms.
- Saturated hydrocarbons have only single bonds between carbon atoms, so the carbon atoms are bonded to as
many hydrogen atoms as possible. In other words, they are saturated with hydrogen atoms. - Unsaturated hydrocarbons have at least one double or triple bond between carbon atoms, so the carbon atoms
are not bonded to as many hydrogen atoms as possible. In other words, they are unsaturated with hydrogen
atoms.
You can learn more about saturated and unsaturated hydrocarbons at this URL: http://www.youtube.com/watch?v=l
9ZieYdLwfo.
MEDIA
Click image to the left for use the URL below.
URL: http://www.ck12.org/flx/render/embeddedobject/5090Uses of Hydrocarbons
It is hard to overstate the importance of hydrocarbons to modern life. Hydrocarbons have even been called the
“driving force of western civilization.” You saw some ways they are used in the opening image. Several other
ways are pictured in theFigure3.56. The most important use of hydrocarbons is for fuel. Gasoline, natural gas,
fuel oil, diesel fuel, jet fuel, coal, kerosene, and propane are just some of the commonly used hydrocarbon fuels.
Hydrocarbons are also used to make things, including plastics and synthetic fabrics such as polyester.
Sources of Hydrocarbons
The main source of hydrocarbons is fossil fuels—coal, petroleum, and natural gas. Fossil fuels formed over hundreds
of millions of years, as dead organisms were covered with sediments and put under great pressure. Giant ferns in
ancient swamps turned into coal deposits. TheFigure3.57 shows one way that coal deposits are mined. Dead
organisms in ancient seas gradually formed deposits of petroleum and natural gas. You can read more about these
sources of hydrocarbons at the URL below.
http://www.energyquest.ca.gov/story/chapter08.html
Summary
- Hydrocarbons are compounds that contain only carbon and hydrogen. Hydrocarbons are the simplest type of
carbon-based compounds. - Hydrocarbons vary greatly in size, which influences properties such as melting and boiling points. At room
temperature, hydrocarbons may be gases, liquids, or solids. They are generally nonpolar and do not dissolve
in water.