2 Objectives of this Unit California Standards:4a. Students know the relative amount of incoming solar energy compared with Earth’s internal energy and the energy used by society.4b. Students know the fate of incoming solar radiation in terms of reflection, absorption, and photosynthesis.4c. Students know the different atmospheric gases that absorb the Earth’s thermal radiation and the mechanism and significance of the greenhouse effect.
3 A. Methods of Energy Transfer 1. Energy transfer as heat can occur in 3 ways:ConductionConvectionRadiation
4 B. Conduction Conduction involves objects in direct contact conduction – the transfer of energy as heat between particles as they collide with one another.conduction takes place when two objects in contact are at unequal temperaturesAtoms in hot objects are moving fast and transfer that energy to nearby atoms that aren’t moving as fast.
6 C. Convection Convection results from movement of warm fluids Convection – the transfer of energy by the movement of fluids with different temperatures.Only possible if substance is a fluid ( liquid or gas) because particles of solid are not free to move.Convection current – circular movement created when hot fluids rise and cold fluids sink.
7 5. Local Winds – air currents created by convection. Sea breeze – hot air above land during day is replaced by cool air over water.land breeze – cool air above land during night is pulled out to replace warmer air rising over water.
8 D. Convection on Earth Air is heated on Earth near Equator. Warm air at equator rises and then moves towards the poles.Cold air sinks near the poles and moves back towards the equator.These convection currents bring warmth from the middle of the planet to the poles.
12 E. RadiationRadiation does not require physical contact between objectsradiation – the transfer of energy by electromagnetic wavesCan feel warmth from a fire even when not in path of convection current due to radiationEnergy transfer in the form of electromagnetic waves includes infrared radiation, visible light, and ultraviolet rays.Radiation does not involve the movement of matter, thus radiation is only method of energy transfer that can occur in a vacuum , such as outer space.
15 F. Conductors Energy is transferred as heat quickly in conductors Energy is passed easily and quickly in most metals, which is why cooking pans are made of metal.conductor – a material through which energy can be easily transferred as heatGases are poor conductors because particles too far apartLiquids are decent conductors, but solids are the best because particles collisions occur more easily.
16 G. Insulators Insulators slow the transfer of energy as heat insulator – a material that is a poor energy conductorEXAMPLE: Skillet made of iron, a good conductor to ensure that energy is transferred effectively as heat to food. However, handle is usually made of a insulator, such as wood, so that energy from hot skillet doe not reach your hand and burn you.
18 H. Energy in Earth System Most energy that reaches Earth’s surface comes from the sun as electromagnetic radiation in form of infrared, visible, and UV rays.Some heat comes from within Earth, but only small amount reaches Earth’s surface.
19 I. 3 Sources of EnergySolar energy (99.985%) – comes from sun (nuclear reactions in sun)Drives wind, ocean currents, and wavesGeothermal energy (.013%) – originates as heat from within Earth from decaying radioactive material.Powers volcanoes, geysers, earthquakes, rock cycleTidal energy (.002%) – energy from pull of moon and sun on Earth’s oceans.Powerful enough to slow down Earth’s rotation
20 J. Energy Distribution on Earth Warmest temp. near equatorSun rays are more concentrated in smaller area near equatorThis occurs because the planet is round.
23 K. Seasons Tilt of Earth on axis; 23.5º Summer – far from sun; yet Earth is tilted towards the sunThus, receives greater concentrations of sun’s rays.Winter – closest to sun; yet Earth is tilted away from sunThus, receives less concentration of sun’s rays.
24 The 23.5 degree TILT is the reason for the seasons!
25 L. Fate of Incoming Solar Radiation AbsorptionLonger wavelengths radiation (infrared) is absorbed by atmospheric gases and clouds.Which gases absorb infrared?_____________________________Shorter wavelengths (visible light) aren’t absorbed by atmosphere, except UV radiation by ozone layer.Carbon dioxide, water vapor, methane, nitrogen oxides
26 L. Fate of Incoming Solar Radiation continued Visible light travels through atmosphere and absorbed by Earth’s surface.1. Absorbed mostly by chlorophyll in plants.2. Visible light used for photosynthesis:Convert carbon dioxide and water into sugar and oxygen.
27 Process that plants do when they absorb solar energy
28 M. Fate of Incoming Solar Radiation cont. 2. ReflectionSome of visible light is reflected back into space by clouds and dust in the atmosphereVisible light is also reflected from Earth’s surface1) Which area of Earth reflects the most sunlight?
29 3. Scatteringa. Some is scattered by dust particles– when light rays are split into many light rays that move in different directionsb. Scattering separates white light into its’ colors.
31 M. Energy coming to and from Earth Most of the energy that comes from sun is in the form of visible light.Most of energy that is reradiated from Earth is in the form of infrared radiation.
32 N. Absorbing atmospheric gases Greenhouse gases: water vapor, carbon dioxide, methane, and some nitrogen oxide pollutantsa. transmit visible light, but absorb infrared light.These gases admit visible light into atmosphere, but inhibit the loss of infrared radiation that is given off from Earth.This is known as greenhouse effect.
35 Q. Energy used by society Humans use energy for:Heating, lighting, transportation, etc.Most of this energy came from solar energy.Stored in fossil fuels (decayed plants), such as oil, natural gas, and coalLimited amounts of these fossils fuels b/c formed over hundreds of millions of years.
36 REVIEW Explain how a Sea and a Land Breeze Work.
38 Review What 3 places the earth get its energy from Review What 3 places the earth get its energy from? Which one has the most?Solar energy (99.985%) – comes from sun (nuclear reactions in sun)Geothermal energy (.013%) – originates as heat from within Earth from decaying radioactive material.Tidal energy (.002%) – energy from pull of moon and sun on Earth’s oceans.