Energy in the Earth System

Objectives of this Unit1. 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.

A. Methods of Energy Transfer

1. Energy transfer as heat can occur in 3 ways:

a. Conduction

b. Convection

c. Radiation

B. Conduction

1. Conduction involves objects in direct contact2. conduction – the transfer of energy as heat

between particles as they collide with one another.

3. conduction takes place when two objects in contact are at unequal temperatures

4. Atoms in hot objects are moving fast and transfer that energy to nearby atoms that aren’t moving as fast.

C. Convection

1. Convection results from movement of warm fluids

2. Convection – the transfer of energy by the movement of fluids with different temperatures.

3. Only possible if substance is a fluid ( liquid or gas) because particles of solid are not free to move.

4. Convection current – circular movement created when hot fluids rise and cold fluids sink.

5. Local Winds – air currents created by convection.

a. Sea breeze – hot air above land during day is replaced by cool air over water.

b. land breeze – cool air above land during night is pulled out to replace warmer air rising over water.

D. Convection on Earth

1. Air is heated on Earth near Equator.

2. Warm air at equator rises and then moves towards the poles.

3. Cold air sinks near the poles and moves back towards the equator.

4. These convection currents bring warmth from the middle of the planet to the poles.

Solar Energy Movie

E. Radiation1. Radiation does not require physical contact

between objects2. radiation – the transfer of energy by

electromagnetic waves3. Can feel warmth from a fire even when not in

path of convection current due to radiation4. Energy transfer in the form of electromagnetic

waves includes infrared radiation, visible light, and ultraviolet rays.

5. 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.

Electomagnetic spectrum

Electromagnetic Spectrum video

F. Conductors1. Energy is transferred as heat quickly in

conductors2. Energy is passed easily and quickly in

most metals, which is why cooking pans are made of metal.

3. conductor – a material through which energy can be easily transferred as heat

4. Gases are poor conductors because particles too far apart

5. Liquids are decent conductors, but solids are the best because particles collisions occur more easily.

G. Insulators

1. Insulators slow the transfer of energy as heat

2. insulator – a material that is a poor energy conductor

3. EXAMPLE: 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.

H. Energy in Earth System1. Most energy that reaches

Earth’s surface comes from the sun as electromagnetic radiation in form of infrared, visible, and UV rays.

2. Some heat comes from within Earth, but only small amount reaches Earth’s surface.

I. 3 Sources of Energy1. Solar energy (99.985%) – comes from

sun (nuclear reactions in sun)a. Drives wind, ocean currents, and waves

2. Geothermal energy (.013%) – originates as heat from within Earth from decaying radioactive material.

a. Powers volcanoes, geysers, earthquakes, rock cycle

3. Tidal energy (.002%) – energy from pull of moon and sun on Earth’s oceans.

a. Powerful enough to slow down Earth’s rotation

J. Energy Distribution on Earth

1. Warmest temp. near equatora.Sun rays are more

concentrated in smaller area near equator

b.This occurs because the planet is round.

Uneven Heating of Earth

K. Seasons1. Tilt of Earth on axis; 23.5º

2. Summer – far from sun; yet Earth is tilted towards the sun

a. Thus, receives greater concentrations of sun’s rays.

3. Winter – closest to sun; yet Earth is tilted away from sun

a. Thus, receives less concentration of sun’s rays.

The 23.5 degree TILT is the reason for the seasons!

L. Fate of Incoming Solar Radiation

1. Absorption

a. Longer wavelengths radiation (infrared) is absorbed by atmospheric gases and clouds.

1) Which gases absorb infrared?

_____________________________

b. Shorter wavelengths (visible light) aren’t absorbed by atmosphere, except UV radiation by ozone layer.

Carbon dioxide, water vapor, methane, nitrogen oxides

L. Fate of Incoming Solar Radiation continued

c. Visible light travels through atmosphere and absorbed by Earth’s surface.

1. Absorbed mostly by chlorophyll in plants.

2. Visible light used for photosynthesis:

a) Convert carbon dioxide and water into sugar and oxygen.

Process that plants do when they absorb solar energy

M. Fate of Incoming Solar Radiation cont.2. Reflection

a. Some of visible light is reflected back into space by clouds and dust in the atmosphere

b. Visible light is also reflected from Earth’s surface1) Which area of Earth reflects

the most sunlight?

3. Scattering

a. Some is scattered by dust particles– when light rays are split into many light rays that move in different directions

b. Scattering separates white light into its’ colors.

Fate of Incoming Solar Radiation

A

C

B

FE

D

M. Energy coming to and from Earth

1. Most of the energy that comes from sun is in the form of visible light.

2. Most of energy that is reradiated from Earth is in the form of infrared radiation.

N. Absorbing atmospheric gases

1. Greenhouse gases: water vapor, carbon dioxide, methane, and some nitrogen oxide pollutants

a. transmit visible light, but absorb infrared light.

2. These gases admit visible light into atmosphere, but inhibit the loss of infrared radiation that is given off from Earth.

a. This is known as greenhouse effect.

The Greenhouse Effect

Q. Energy used by society

1. Humans use energy for:

a. Heating, lighting, transportation, etc.

2. Most of this energy came from solar energy.

a. Stored in fossil fuels (decayed plants), such as oil, natural gas, and coal

b. Limited amounts of these fossils fuels b/c formed over hundreds of millions of years.

REVIEWExplain how a Sea and a Land Breeze Work.

Review Explain the Greenhouse Effect

Review What 3 places the earth get its energy from? Which one has the most?

1. Solar energy (99.985%) – comes from sun (nuclear reactions in sun)

2. Geothermal energy (.013%) – originates as heat from within Earth from decaying radioactive material.

3. Tidal energy (.002%) – energy from pull of moon and sun on Earth’s oceans.

Review Why do we have different seasons?

Review What are the different fates of incoming solar radiation?

Review What does photosynthesis need to make Oxygen and Water?

3. ________________

Review Why is the Equator warmer than the poles?

Review Explain where conduction, convection, and radiation can be seen in this picture.