Chapter 7 Resources and Energy 7.2 Nonrenewable Resources EARTH & SPACE SCIENCE Chapter 7 Resources and Energy 7.2 Nonrenewable Resources

7.2 Nonrenewable Resources Objectives Explain why coal is a fossil fuel. Describe how petroleum and natural gas form and how they are removed from the Earth. Summarize the processes of nuclear fission and nuclear fusion. Explain how nuclear fission generates electricity.

Fossil Fuels Nonrenewable resources are resources that form at a rate that is much slower than the rate at which it is consumed. A fossil fuel is a nonrenewable energy source that formed form the remains of organisms that lived long ago. Petroleum, coal, and natural gas are fossil fuels. Fossil fuels are made primarily from hydrocarbons.

Fossil Fuels The energy contained in hydrocarbons is in the form of the bonds between the hydrogen and the carbon atoms. The hydrocarbons represent chemical energy that was formed in organisms millions of years ago from sunlight being captured and converted. Coal is the most commonly burned fossil fuel. Coal is the concentrated remains of plants that have gone through carbonization.

Fossil Fuels In the process of carbonization, partially decomposed plant matter is buried in mud and becomes peat. Bacterial decomposition continues to release methane and carbon dioxide. As gases escape, the concentration of remaining hydrocarbons increases. The process of carbonization occurs in the absence of oxygen.

Fossil Fuels As peat is buried and loses water and gas content, it becomes lignite. Lignite may be further compressed into bituminous coal. If enough temperature and pressure is applied to bituminous coal, it may become anthracite. The energy found in these products increases as the transformation is made from peat, to lignite, to bituminous coal, to anthracite.

http://www.stovesonline.co.uk/how-coal-formed.html

Fossil Fuels Microorganisms and plants, as they would die, they would accumulate on the bottom of lakes and oceans and become buried in sediment. Heat and pressure would gradually increase with the accumulation of more and more sediment overburden. Millions of years of heat and pressure result in chemical changes that convert those remains into petroleum and natural gas. Both petroleum and natural gas are rich in hydrocarbons.

Fossil Fuels Transportation, farming, and many other industries rely on fossil fuels. Petroleum and natural gas are often taken from permeable sedimentary rocks. Pressure forces fluids (including oil and gas) up through permeable rocks. When the fluids reach an impermeable cap rock, they accumulate in a reservoir and become stratified according to density.

http://www. utexas. edu/depts/grg/huebner/Spring2003/grg306c/Coal_Oil http://www.utexas.edu/depts/grg/huebner/Spring2003/grg306c/Coal_Oil.htm

http://www.uwsp.edu/geo/faculty/ozsvath/images/oil_and_gas_reservoirs.htm

Fossil Fuels Geologists look for structures that would trap oil and gas. If a well is drilled into a reservoir, oil and gas are often forced to the surface by pressure. http://www.uwsp.edu/geo/faculty/ozsvath/images/oil_gusher.htm

Fossil Fuel Supplies Fossil fuels, though a nonrenewable resource, are a major source of energy globally. Crude oil is also used in the production of plastics, medicines, synthetic fabrics, waxes, synthetic rubber, insecticides, chemical fertilizers, shampoos, detergents, and other products. Coal is globally the most abundant fossil fuel. The United States, Russia, and China have two-thirds of the known coal reserves globally.

Fossil Fuel Supplies It is likely that most of the petroleum reserves on Earth have been discovered. Many new gas reserves are likely to be discovered and much oil shale still lies beneath Earth’s surface. http://origin.mars5.jpl.nasa.gov/classroom/schoolhouse/rocklibrary/index3.html

http://www.mines.edu/research/ceri/oil%20shales.html

Nuclear Energy Nuclear energy is energy produced by manipulation of the nuclei of atoms – matter contains a great deal of energy. Nuclear fission is the process in which the nucleus of a large atom is split into two or more fragments releasing neutrons and energy. The forces that hold the nucleus of an atom together are about a million times stronger than the chemical bonds between atoms. A neutron is fired into the nucleus of a large atom to cause a split releasing energy and other neutrons that may split other atoms. The result is a chain reaction.

http://www.uraniumminerals.com/UTh/U http://library.thinkquest.org/C003730/index.php3?ID=18

Nuclear Energy An uncontrolled chain reaction results in an explosion – like an atomic bomb. Controlled nuclear fission can be used to generate electricity. http://www.digitalhistory.uh.edu/do_history/decisions/hiroshima.html

Nuclear Energy An enriched fuel source, typically uranium 235, is formed into pellets and contained in fuel rods. The fuel rods are housed in the reactor core which also contains control rods that contain cadmium or boron (for absorbing neutrons) which are used to slow down the chain reaction. The plant “powers up” to increase the heat by allowing the reaction to occur more freely and “powers down” to slow the reaction and cool the reactor. Water is pumped around the fuel rods to absorb the heat and then routed to a second circuit where the heat is transferred to water in the secondary unit to produce steam.

Nuclear Energy The steam is then used to turn the turbines of electrical generators. A third circuit of water carries away the excess heat and cools the water before it can be released into the environment. If the water is too hot when it is released into the environment, it is considered to be thermal pollution.

Nuclear Energy Advantages of nuclear fission power plants. No air pollution More uranium than oil available Reduced dependence on foreign oil Building new plants = jobs Disadvantages of nuclear fission power plants. Radioactive waste products Security of waste products and fuel source Expensive to build Currently there are only three disposal facilities in the U.S. – much of the nuclear waste is stored in onsite water pools

http://www.uni.edu/darrow/wind

Nuclear Energy Nuclear fusion is the process by which the nuclei of small atoms are joined together to form a new, more massive nucleus. Nuclear fusion is the process that powers stars as hydrogen nuclei fuse to form helium nuclei. Fusion reactions require temperatures over 15,000,000 °C to occur. If scientists can figure out how to control such a high energy environment, hydrogen from ocean water could be a fuel source with helium as the waste product.