Unit 2: Energy in Earth Systems Preview Objectives Earth’s four spheres Earth’s energy budget Nonrenewable Energy Fossil Fuels Types of Coal Oil Traps Fossil-Fuel Supplies Nuclear Energy A Nuclear Fission Reaction Parts of a Nuclear Reactor

Earth’s Four Spheres Matter on Earth is in solid, liquid, and gaseous states. The Earth system is composed of four “spheres” that are storehouses of all of the planet’s matter. The Atmosphere atmosphere a mixture of gases that surrounds a planet or moon The atmosphere provides the air you breathe and shields Earth from the sun’s harmful radiation.

Earth’s Four Spheres, continued The Hydrosphere hydrosphere the portion of Earth that is water Water covers 71% of Earth’s surface. Water in the hydrosphere occur in the form of oceans, lakes, rivers, streams, glaciers and ice sheets, and groundwater.

Earth’s Four Spheres, continued The Geosphere geosphere the mostly solid, rocky part of Earth; extends from the center of the core to the surface of the crust The geosphere includes all of the rock and soil on the surface of the continents and on the ocean floor. The geosphere also includes the solid and molten interior of Earth.

Earth’s Four Spheres, continued The Biosphere biosphere the part of Earth where life exists; includes all of the living organisms on Earth The biosphere is composed of all of the forms of life in the geosphere, in the hydrosphere, and in the atmosphere, as well as any organic matter that has not decomposed. The biosphere extends from the deepest parts of the ocean to the atmosphere a few kilometers above Earth’s surface.

Earth’s Energy Budget The transfers of energy between Earth’s spheres can be thought of as parts of an energy budget. The first law of thermodynamics states that energy is transferred between systems, but it cannot be created or destroyed. The second law of thermodynamics states that when energy transfer occurs, matter becomes less organized with time. Thus, the universe’s energy is spread out more uniformly over time. The constant exchange of matter and energy between Earth’s spheres happens through chemical reactions, radioactive decay, the radiation of energy ,and the growth and decay of organisms.

Earth’s Energy Budget, continued The figure below shows Earth’s energy budget.

Earth’s Energy Budget, continued Reading Check Define energy budget. An energy budget is the total distribution of energy to, from, and between Earth’s various spheres.

Earth’s Energy Budget, continued Internal Sources of Energy When Earth formed about 4.6 billion years ago, its interior was heated by radioactive decay and gravitational contraction. The decay of radioactive atoms still generates enough heat to keep Earth’s interior hot. Earth’ interior also retains much of the energy from the planet’s formation. By the process of convection, the heat in Earth’s interior is transferred through the layers of Earth and is released at Earth’s surface.

Earth’s Energy Budget, continued External Energy Sources Earth’s most important external energy source is the sun. Solar radiation warms Earth’s atmosphere and surface. This heating causes the movement of air masses, which generates winds and ocean currents. Many chemical reactions on Earth also require solar energy. Another important external source of energy is gravitational energy from the moon and sun. This energy helps generate tides that cause currents and drive the mixing of ocean water.

Nonrenewable Energy

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

Nonrenewable Energy nonrenewable resource a resource that forms at a rate that is much slower than the rate at which it is consumed Fossil Fuels fossil fuel a nonrenewable energy resource that formed from the remains of organisms that lived long ago; examples include oil, coal, and natural gas Much of the energy humans use every day comes from the burning of the hydrocarbons that make up fossil fuels. When hydrocarbons are burned, the breaking of chemical bonds releases energy as heat and light.

Fossil Fuels Formation of Coal Coal is the most commonly burned fossil fuel, formed during a complex process called carbonization. Carbonization occurs when partially decomposed plant materials is buried in swamp mud and becomes peat. As bacteria consume some of the peat and release the gases methane, CH4, and carbon dioxide, CO2, the contents of peat gradually change until mainly carbon remains. Peat remains if conditions are not optimal for carbonization. Peat may be used as an energy source.

Types of Coal The diagram below shows the different types of coal.

Fossil Fuels, continued Types of Coal Deposits The partial decomposition of plant remains forms a brownish-black material called peat. Peat is buried by other sediment. As heat and pressure increase peat becomes lignite. Lignite is also called brown coal. Increased temperature and pressure compacts the lignite and forms bituminous coal. Bituminous coal is made of 80% carbon. Anthracite, the hardest form of coal, is produced when bituminous coal is under high temperatures and pressures. Anthracite coal is made of 90% carbon.

Fossil Fuels, continued Formation of Petroleum and Natural Gas Petroleum and natural gas are mixtures of hydrocarbons. These fossil fuels formed when heat and pressure caused chemical changes to the remains of microorganisms and plants. Petroleum and Natural Gas Deposits Petroleum and natural gas are very important sources of energy for transportation, farming, and many other industries. They are mined from permeable sedimentary rocks. Petroleum accumulates beneath cap rock and fill the space to form an oil reservoir. Natural gas rises above petroleum, because it is less dense than both oil and water.

Oil Traps The diagram below shows how oil becomes trapped under cap rock.

Fossil Fuels, continued Oil Traps When a well is drilled into an oil reservoir, the petroleum and natural gas often flow to the surface. After the pressure of the overlying rock is removed, fluids rise up and out through the well.

Fossil-Fuel Supplies Fossil fuels, like minerals, are one of the main sources of energy, but are also nonrenewable resources. Crude oil, or unrefined petroleum, is also used in the production of plastics, synthetic fabrics and rubber, medicines, waxes, chemical fertilizers, detergents, shampoos, and many other products. Coal is the most abundant fossil fuel in the world. Two-thirds of the known deposits of coal occur in the United States, Russia, and China. Oil shale is a relatively abundant material that contains petroleum. But the cost of mining oil from shale is far greater than the present cost of recovering oil from other sedimentary rocks.

Reading check What is cap rock? Cap rock is a layer of impermeable rock at the top of an oil or natural gas-bearing formation through which fluids cannot flow.

Nuclear Energy The energy that is produced from nuclear reactions is called nuclear energy. Scientists discovered that atoms had smaller fundamental parts. These parts could be split by creating nuclear reactions with nuclear technologies.

Nuclear Energy, continued Nuclear Fission nuclear fission the process by which the nucleus of a heavy atom splits into two or more fragments; the process releases neutrons and energy. When the nucleus splits, it releases additional neutrons as well as energy. The newly released neutrons begin a chain reaction by striking nearby nuclei, which causes those nuclei to split and release more neutrons and more energy. If left uncontrolled, a fission reaction will escalate quickly and may result in an explosion. Controlled reactions produce heat that can be used to generate electricity.

Reading check, continued What causes a chain reaction during nuclear fission? As neutrons strike neighboring nuclei, the nuclei split and release additional neutrons that strike other nuclei and cause the chain to continue.

Nuclear Energy, continued How Fission Generates Electricity A nuclear reactor is a specialized equipment in which controlled nuclear fission is carried out. Currently, uranium-235, or 235U, is the only naturally occurring element used for nuclear fission. This ore is mined and processed into fuel pellets with high 235U content. These uranium-enriched pellets are placed into rods to make fuel rods. Bundles of these fuel rods are then bombarded by neutrons to induce a nuclear reaction.

Nuclear Energy, continued How Fission Generates Electricity, continued The resulting chain reaction from nuclear fission causes the fuel rods to become very hot. Water is pumped around the fuel rods to absorb and remove heat energy. The water is then pumped into a second circuit, where it becomes steam and turns the turbines that provide power for electric generators. A third water circuit carries away the excess heat and releases it into the environment.

A Nuclear Fission Reaction The diagram below shows how a nuclear fission reaction.

Nuclear Energy, continued Advantages and Disadvantages of Nuclear Fission Nuclear power plants burn no fossil fuels and produce no air pollution. However, they produce harmful radioactive materials that have very long half-lives, wastes must be stored for thousands of years. These waste products give off harmful doses of radiation that can destroy plant and animal cells and can cause harmful changes in the genetic material of living cells.ystem is a system in which both energy and matter are exchanged with the surroundings.

Nuclear Energy, continued Nuclear Fusion nuclear fusion the process by which nuclei of small atoms combine to form new, more massive nuclei; the process releases energy All of the energy that reaches Earth from the sun is produced by nuclear fusion. Fusion reactions only occur at temperatures of more than 15,000,000°C. The only byproduct of fusion are helium nuclei, which are harmless to living cells.

Parts of a Nuclear Reactor