Thermal Energy Transfer and the Sun

1. Thermal Energy Transfer and the Sun

2. Thermal Energy and Climate

3. Thermal Energy Transfer BACKGROUND INFO: • All things are made up of molecules • When things get heated, they absorb heat energy • With more energy, molecules are able to move faster • When molecules move faster, the temperature rises

4. What is Thermal Energy??? • Thermal Energy is energy resulting from the motion of particles • It is a form of kinetic energy and is transferred as heat • Thermal Energy Transfer can occur by three methods: • Conduction • Convection • Radiation • View the following animation to get an overview of these processes: heat transfer

5. Conduction • Conduction is the transfer of thermal energy through direct contact between particles of a substance, without moving the particles to a new location • Usually occurs in solids

6. Conduction • View: Conduction in Solids • When heat is supplied to one end, molecules at that end start to move more quickly • In the process, they bump into their neighbours, transferring the kinetic energy • And so on, and so on…… • Why is this less likely in liquids and gases?

7. Convection • Convection is the transfer of thermal energy through movement of particles from one location to another • Usually occur in fluids (liquids and gases)

8. Convection • Example with boiling water: • Water at bottom of pan is heated first • Heated water expands and density decreases • Heated water begins to rise • Cooler water with higher density from the sides of the pan rush down to take its place • The cooler water gets heated and the cycle repeats • We call these Convection Currents

9. Radiation • Radiation is the emission of energy as waves or particles or rays • Radiation does not require a medium to transfer energy • Radiant energy is either reflected or absorbed by matter • Energy that is absorbed increases the kinetic energy of the object • This increases the temperature of the object

10. Radiation • Example … the Sun • Sun radiates energy in form of solar radiation • When this energy reaches Earth, it is absorbed by matter (air, water, land) • Absorbed radiant energy increases kinetic energy of the matter, raising its temperature

11. Radiation • The Sun is an emitter • It gives out heat • The Earth is an absorber • It takes in the heat

12. Balance of Energy on Earth • Almost all energy on Earth comes from the sun • Electromagnetic spectrum, including infrared radiation and UV radiation

13. Earth Absorbs Energy from the Sun • When solar radiation contacts a particle of matter, one of three things happens: • Radiation is absorbed by a particle, causing the particle to gain energy • Radiation is transmitted through the particle • Radiation is reflected off the particle

15. Net Radiation Budget Break down of the Radiation that reaches Earth (by percentage): • 30% reflected back into space by clouds, atmosphere and Earth’s surface • 30% of remaining 70% is absorbed by the atmosphere • The rest (40% of 70%) warms the Earth’s surface: • Returns heat to atmosphere as infrared radiation, thermal energy and water vapour

16. Net Radiation Budget • Net Radiation Budget  the difference between the amount of incoming radiation and the amount of outgoing radiation Net radiation budget = incoming radiation – outgoing radiation = zero (theoretically) • Do all regions on Earth have a zero net radiation? Explain! • Not all regions have a balanced radiation budget (but Earth as a whole does) • E.g. polar regions have less incoming than outgoing radiation • E.g. tropics have more incoming than outgoing radiation

17. Factors Affecting Radiation • ALBEDO • Colour of the surface • Albedo is the percentage of the incoming solar radiation that it reflects • Albedo of Earth is about 30% • Light-coloured, shiny objects reflect more solar radiation and have a high albedo (ice, snow, sand) • Ice and snow reflect heat because they are white. They reflect so much of the Sun’s energy that it is hard for these locations, like the Arctic, to get very warm. • Darker, dull objects absorb more solar radiation and have a low albedo (forests, soils)

18. Factors Affecting Radiation • Surface Temperature • The higher the surface temperature, the higher the rate of transfer • Surface Area • The larger the surface area, the higher the rate of transfer

19. In Summary • Three methods of Heat Transfer • Convection, conduction, and radiation • Earth’s Net Radiation Budget = “zero” • Factors affecting radiation: • Albedo • Surface temperature • Surface Area

20. Homework Page 1 of 2 The amount of the energy the Earth absorbs is equal to the amount of energy it radiates. Why is this important? Explain. [Knowledge] 2. The Sun shines continuously on Earth. Explain why Earth does not keep warming up. [Thinking] a) Describe what happens to the Sun’s energy once it reaches Earth. [Knowledge]b) Describe what happens to the energy Earth emits. [Knowledge] 4. What would you expect to happen to the temperature of Earth if [Thinking]a) the amount of energy radiated by Earth increased but the amount of energy coming from the Sun stayed the same?b) the amount of energy radiated by Earth decreased but the amount of energy coming from the Sun stayed the same? 5. State two reasons why you would expect the climate in Nigeria to be warmer than the climate in Greenland. [Thinking/Application]

21. Homework Page 2 of 2 6. Explain why the greenhouse effect is important to life on Earth. [Knowledge] 7. Describe how the greenhouse effect in the atmosphere works and draw a diagram illustrating it. [Thinking] 8. a) Write a definition, in your own words, of “greenhouse gas”. [Knowledge]b) Name the two most important greenhouse gases that occur naturally in the atmosphere. [Knowledge] 9. If forests serve as important sinks for greenhouse gases, describe how past ice ages might have affected the concentration levels of carbon dioxide in the atmosphere. [Application] 10. Give one natural source for each of the following greenhouse gases: [Application]a) carbon dioxideb) methanec) nitrous oxided) water

22. Just For Fun Go to the Ecokids.ca Climate Change Games and Activities. Spend ~ 5minutes playing each of the games listed as “Intermediate”. Identify one new thing you learned by playing the games that surprised you about climate change. Why were you surprised?