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Energy Transfer in Spheres

Energy Transfer in Spheres. Guiding Questions:. How do we describe types of energy? Is there anything that doesn’t require energy? How does energy transfer influence our environment? How do human activities influence energy transfer? (is it for the better and/or the worse?).

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Energy Transfer in Spheres

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  1. Energy Transfer in Spheres

  2. Guiding Questions: • How do we describe types of energy? • Is there anything that doesn’t require energy? • How does energy transfer influence our environment? • How do human activities influence energy transfer? (is it for the better and/or the worse?)

  3. What is the role of the Sun’s energy in Earth’s spheres? Key Concepts: • Solar energy that reaches Earth is absorbed and reflected by Earth’s atmosphere and surface • Solar energy heats Earth’s surface unevenly and global winds and ocean currents help redistribute thermal energy around Earth • Solar energy enters the biosphere through photosynthesis and cellular respiration

  4. Heat and Thermal Energy

  5. Heat & Thermal Energy Kinetic Molecular Theory (KMT): • all matter is made of particles • particles are in constant motion • the more energy the particles have, the faster and farther apart they move • Kinetic energy: energy in (or due to) motion • Potential energy: stored energy

  6. Temperature influences our everyday lives • Temperature:is the measure of average kinetic energy of a substance.

  7. Factors that affect kinetic energy: 1. solids vs gases at different temps • particles in a gas move faster than particles in a solid at the same temperature • a gas at -50oC will have less kinetic energy than a solid at 500oC because the gas molecules are moving more slowly 2. mass of the particles • the larger the particle, the more energyit has vs. a smaller particle moving at the same speed • but a very fast, smaller particle may have morekinetic energy than a very slow, large particle • other factors: pressure, atmosphere, density

  8. Thermal energy: total kinetic energy and potential energy of all the particles in a substance Ex: which has more thermal energy? cup of tea @ 80oC vs pot of water @ 50oC

  9. Pot – has less temperature, but more thermal energy than the cup because of more particles Cup – has more temperature than the pot, but less thermal energy because of fewer particles

  10. Heat: the transfer of thermal energy from one object to another • Note: objects don’t have heat, only thermal energy • Caused by difference in temperature between molecules. • the transfer of thermal energy is always from hotter to colder objects

  11. Describe the heat transfer in these photos: • if an object “pulls” heat away from us, it feels ‘cold’ • if an object “gives” heat to us, it feels ‘warm’

  12. Popcorn Example • There are three types of heat transfer: • Conduction • Convection • Radiation

  13. Heat Transfer: 1. Conduction: transfer of thermal energy by direct particle to particle contact • Transfer is from higher to lower energy/temperature particles • Transfer process will continue until equilibrium, balancereached in energy content.

  14. Examples of Conduction: • A spoon in hot tea: tea particles transfer energy to a metal spoon, the spoon heats up and the fast moving tea particles slow down, resulting in a cooler tea temperature • Ice cube in a soft drink: Warmer pop particles transfer energy into the ice particles, causing the ice to melt, while the pop cools down.

  15. 2. Convection: transfer of thermal energy by movement of heated, fluid particles. The heated particles increase the average kinetic energy. • Convection works well in some liquids and most gases • In “closed” systems, the convection cycle process will continue until all the particles are the same temperature

  16. Convection currents move thermal energy through the spheres: atmosphere, oceans, and earth’s mantle. These are “open” systems so a balance, equilibrium of temperature can not be reached.

  17. Describing Convection: 1. Large pot of water over a heat source (not directly touching it) Water particles heat & rise, pushing cooler particles to the bottom, these in turn heat & rise, causing a convection current 2. Room with a heater Heated air is less dense, it expands and rises to ceiling. Then it cools and starts to fall to the floor. Cooler air moves towards the heater and cycle continues

  18. Diagram

  19. Examples of Convection: 1. Warmer water at the surface of a lake 2. Wind currents 3. Hot air balloons 4. Hot air rises in a house so 2ndstorey is warmer

  20. 3. Radiation:energy is transferred by electromagnetic waves in the absence of matter, even through empty space. • radiation thermal energy is found in radio waves, microwaves, infrared, visible light, U.V., X-Rays, and Gamma rays. • radiation that is absorbed turns into thermal energy. If it is reflected no transfer of energy occurs. • Solar radiation: transfer of radiant energy from the sun • Ex. Skin feeling warm due to sunlight

  21. Examples of Radiation energy transfer: • a campfire • A microwave oven • A lightbulb *objects that are good absorbers of radiation are good radiators as well

  22. Demonstrating energy currents

  23. Conductors vs. Insulators of Thermal Energy Conductors: materials that allow the transfer of thermal energy Good conductors – metals, some liquids (mercury, oils) Poor conductors – glass, wood, plastics, most liquids (water), most gases (molecules are far apart therefore no collisions or transfer of energy between the 2 substances)

  24. Insulators: materials that slow down thermal energy transfer • Styrofoam • Fibreglass insulation • Air spaces between window & thermoses

  25. Application: • Give two everyday examples of using a conductor for thermal energy transfer: • Give two everyday examples of using an insulator to slow down thermal energy transfer: • Think of examples in the home of how using a conductor or insulator can save money

  26. Materials absorb, reflect, or transmit radiation. Heat is transferred when a substance absorbs radiation, causing it to increase in temperature, melt or evaporate.

  27. Earth’s Heat Sources thermal energy comes from 2 directions: • from below – Earth’s core is 7000 oC and internal radioactive decay of elements generates heat which is transferred to volcanoes, hot springs, & geysers. It is also believed that there is residual thermal energy from Earth’s formation.

  28. Earth’s Heat Sources • from above – solar energy (radiant energy that is absorbed, not transmitted or reflected, is converted to thermal energy)

  29. Thermal energy in the atmosphere

  30. Only a tiny portion of solar radiation reaches Earth • Solar radiation is converted to thermal energy • Insolation: amount of solar radiation that reaches a certain area • Locations at higher latitudes receive less insolation

  31. Solar radiation comes in short wavelengths, some of which pass through the atmosphere to Earth’s surface where they are absorbed • Earth’s surface reradiates some of this energy in longer, infrared waves

  32. Albedo: the amount of radiation reflected by a surface • Snow-covered areas (ice) and deserts have high albedos • Forests and soils have low albedos • Human activities can change albedo of Earth’s surface (Air pollution)

  33. Which is better? • Should earth have a high or low albedo?

  34. Greenhouse effect • Absorption of outgoing thermal energy by the atmosphere • It keeps earth’s temperature within a certain range • Greenhouse gases – absorb and emit radiation as thermal energy Ex: water vapour, carbon dioxide, methane, nitrous oxide

  35. Radiation is the primary way that air in the atmosphere is heated. The sun’s rays heat the ground air which rises. • Convection currents then move the heated air around the earth and the differences between warm & cool air create weather

  36. Redistribution of Thermal Energy around Earth

  37. Solar energy is largely responsible for creating and influencing 3 things necessary for life: warmth, winds, and water movement • Recall: radiation is the primary way that air is heated. Convection currents move the heated air around the earth and the difference between warm and cold air provide the energy needed to create weather

  38. 1. Warmth • Unequal heating of Earth • Caused by the tilt of earth’s axis at 23.5o Summer Winter

  39. Seasonal temperature differences are due in large part to the angle at which the sun’s rays strike earth’s surface

  40. The same amount of light energy reaches all parts of the earth but at the poles, the light strikes the earth at a slanted angle and is spread out over a larger surface area. The result is lower temperatures.

  41. 2. Global Wind Systems • Unequal heating of Earth requires redistribution of the thermal energy • Global wind systems move thermal energy around Earth and distribute it more evenly throughout the atmosphere

  42. Prevailing Winds Prevailing Winds: are caused by convection currents produced by differences in high and low pressure cells • Uneven heating of earth’s surface causes the convection currents to form, mainly originating at the equator

  43. The winds blow in consistent patterns over large portions of the globe • Wind is named for the direction it comes fromex. Easterlies, Westerlies, NE and SE trade winds • Jet streams are prevailing winds (high speed westerly winds) in the upper atmosphere • Directions of Earth’s wind systems vary with the latitudes in which they occur

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