1. Energy Budget

2. Modes of Energy Travel Heat Energy can travel in three specific ways: Conduction Convection Radiation Since conduction and convection require a medium through which to travel, radiation is the method by which we on Earth receive the Sun’s energy.

3. Electromagnetic Radiation

4. When radiant solar energy reaches the Earth, 2 different interactions occur: Reflection – the radiation is reflected back into space unchanged Absorption – the radiation is absorbed by the atmosphere of the Earth’s surface. 70% absorbed 30% reflected The amount of the Sun’s energy that hits 1m² of the Earth’s surface every second is called the solar constant. (1367J/m²s)

5. Breakdown

6. Earth’s “Constant” Temperature The Earth retains a relatively constant temperature. To do this, it must radiate as much energy back to space as it absorbs from the Sun. The time between the absorption of the Sun’s energy and the subsequent radiation of it back into space drives our weather systems.

8. Questions 1. What is the only way energy can travel from the Sun to the Earth? Explain why. 2. Name the categories of Energy emitted from the Sun. 3. Define the term solar constant. 4. How does the Earth remain at a “constant” temperature?

9. Energy and Water The interactions between radiant energy and water that occur depend on the state of the water. White snow reflects up to 90% of the incoming solar energy Ice reflects about 50% Liquid water reflects only about 7% (i.e. it absorbs about 93%!!!) However, temperature of these bodies of water do not vary a great deal.

10. Specific Heat Capacity. This is defined as the amount of energy (heat) required to raise the temperature of one gram of substance by one degree Celcius. Some examples: Pure water 4.18 J/g·ºC Salt water 3.89 J/g·ºC Dry Air 1.00 J/g·ºC Wet Mud 2.15 J/g·ºC

11. Heat of Vaporization This is yet another characteristic of water that helps it to maintain its constant temperature. This is defined as the amount of energy that is required to convert 1.0g of a substance from a liquid state to a gaseous state. HOV for water = 2260 J/g HOV for methanol = 1076 J/g

12. Heat of Fusion The amount of heat required to melt 1.0g of a solid into a liquid (in reverse, it is the amount of energy released when 1.0g of a liquid becomes solid!) HOF for water = 333 J/g HOF for methanol = 100 J/g

13. Questions 1. Explain how the heat capacity of water effects the temperature of a large lake. 2. Define “Heat of Vaporization.” 3. What type of energy change occurs when liquid water freezes?