UNIT FIVE

ENERGY INEARTH’S PROCESSES

Energy from the Sun

•Energy is the ability to do work.

•Everything that happens in the universe involves work in some fashion.

•We can think of the earth like a machine that is “driven” by two “heat engines” one that is internal and one that is external.

•The external heat engine drives most of our surface process and is powered mainly by energy from the sun.

•Heat from the core of the earth and the resultant mechanical energy is the internal source of Earth’s energy.

•Electromagnetic energy is a type of energy that is radiated in the form of transverse waves from all matter not at absolute zero. This is the type of energy radiated by the sun; in fact, by all stars.

•A wavelength is the distance from the crest of one wave to another. It can also be described as the distance between any two corresponding points on a successive cycle.

EmE

•Visible light is the only wavelength in the electromagnetic spectrum that can be seen by the human eye.

•Infrared energy is often felt due to its heating effects.

•Ultraviolet radiation tans or burns the skin; and can cause cancers, blindness and/or tissue mutations with prolonged exposure.

EmE and the Atmosphere

•When EmE comes into contact with a material, the waves of energy interact with that material.

•Depending upon the material and the angle of interaction, a number of possibilities can occur.

Refraction

•or bent…causing the direction of the waves to change.

Reflection

•or bouncing off of the material…causing the energy to return in the direction from which it came.

Scattered

•sent in all directions…this is a combination of all the interactions mentioned.

Transmission

•or passing through the material…continuing on in the same direction unchanged.

Absorption

•or taken into….energy is taken into a material and is sometimes transformed and reradiated at a longer wavelength.

Absorption and Earth’s Surface

•The type of surface influences how much of the EmE from the sun is absorbed.

•The darker the color of the surface, the more visible light it will absorb.

•The rougher a surface is, the more energy it will absorb and the less it will reflect.

•Mirrors are shiny because they are smooth and reflect most of the incoming visible light.

•The more effective a material is at absorbing energy, the better it is at radiating (or giving off) the energy.

•A dark colored object will heat up quickly in sunlight and cool down quickly after sunset.

** A good absorber is a good radiator and heats up and cools down quickly.

** A poor absorber is a poor radiator and heats up and cools down slowly.

Transfer of Energy

•Energy moves from a region of high concentration (the source) to a region of low concentration (the sink).

•Energy will continue to move from high to low until the energies are equal, establishing a state of dynamic equilibrium.

Methods of transfer

•The transfer of heat energy from atom to atom or molecule to molecule when atoms/molecules vibrate or collide is conduction.

•Conduction is most effective in solids – especially metals – because the atoms are closer together than in gases and liquids.

•The transfer of heat energy by movement in fluids – gases and liquids – caused by the differences in density within the fluid is convection.

•Warmer portions have lower densities and tend to rise above the cooler portions.

•The higher density portions are pulled down and displace the less dense portions, pushing them upward

•The result of this motion is a convection current which is a circulatory movement that transfers heat energy from one place to another.

•Radiation is the method by which heat energy is transferred through electromagnetic waves. No medium is needed to transfer the energy.

•This energy can radiate from its source across empty space. This is how the EmE from the sun travels through space to Earth and the rest of our solar system.

Transformation of Energy

•A transformation of energy is the change of one type of energy into another type.

•Transformation of energy often occurs when there is friction.

•When friction occurs, some of the kinetic energy is transformed into heat energy. At the interface wherever friction occurs, heat (and sometimes sound) is formed

•Mechanical energy can be defined as the total of the potential and kinetic energy of an object or system.

•An object in motion has kinetic energy. The faster it moves and the more mass it has, the greater its kinetic energy.

•Potential energy is energy related to position or phase. It can be thought of as stored energy. The farther an object is from the center of the earth, the greater its potential to fall and the greater its potential energy.

•There is a direct relationship between the amount of mass and the possible potential energy….as mass increases, potential energy increases as well.

•An example of wavelength transformation is when EmE is absorbed by an object and reradiated at a longer wavelength.

•This type of transformation is common on the surface of the earth when shorter wavelength ultraviolet and visible radiation from the sun are absorbed and reradiated as longer wavelength infrared radiation.

Measuring Heat Energy

•Temperature is a measure of the average kinetic energy of the particles of matter. It is not a type of energy…but a measure of energy!

•The greater the average kinetic energy of the particles, the higher the temperature.

•The type of energy that is transferred from hot to cold objects is heat energy and is measured in joules (a metric unit of energy or work)

•The amount of heat energy needed to raise the temperature of one gram of any substance 1ºC is called the specific heat of that substance.

•It can be thought of as the resistance of a material to heating up or cooling off.

** See page one of your ESRT•Liquid water has the highest specific heat of any naturally occurring substance.

•Because of this, water heats up and cools down slowly!

•Therefore...large bodies of water have a moderating effect on climate!

•The higher the specific heat the more slowly the material changes temperature!

•The lower the specific heat, the more rapidly the material changes temperature!

Energy and Phase Changes

•An increase or decrease in the energy and temperature of matter can cause the material to go from one phase to another.

•Melting is the change in phase from a solid to a liquid.

•Solidification (or freezing) is the change in phase from a liquid to a solid.–Solidification that results in an organized pattern of atoms is called crystallization.

•Evaporation (or vaporization) is the change in phase from a liquid to a gas (vapor).

•Condensation is the change in phase from a gas (vapor) to a liquid

•Sublimation is the changing of a gas directly to a solid or from a solid directly to a gas.

•When water changes phase from a solid to a liquid to a gas, it absorbs heat energy; molecular movement speeds up and molecules spread out.

•When water changes phase from a gas to a liquid to a solid, it releases stored heat; molecular movement slows down and molecules move closer together.

•While a material remains in one of the phases of matter, its temperature increases as heat energy is added.

•If the material is in the process of changing phase, its temperature remains the same as it is heated.

•During the phase change, the added heat energy is not increasing the kinetic energy the temperature is not increasing.

•The added heat energy is being converted to a type of potential energy called latent heat.

Earth’s Energy

•The sun radiates energy in a variety of wavelengths among which are ultraviolet rays, visible light and infrared rays. Visible light is received at the greatest intensity.

•Nuclear fusion generates energy within the sun and provides us with our external heat source

•Heat energy from the Earth’s core is converted into mechanical energy for geological processes such as mountain building, plate movements and volcanic eruptions.

•It is believed that most of the Earth’s interior energy comes from the nuclear decay of radioactive materials in Earth’s core

•Nuclear fission is the process by which unstable or radioactive atomic nuclei split to form lighter elements.

•In the process, large amounts of energy are released.

•Another source of Earth’s energy is the energy created by the impact of meteoroids, asteroids and comets with Earth’s atmosphere and surface

•There are many other minor sources of energy including the gravitational energy of the Sun and Moon which creates the tidal energy of the oceans as well as many sources of friction.