ch02 - Jon Ahlquist 9/17/2006 Chapter 2 Energy: Warming the...

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Jon Ahlquist 9/17/2006 MET1010 Intro to the Atmosphere 1 Chapter 2 Energy: Warming the Earth and the Atmosphere Energy (pp. 28-29 + extra not in book) ± Energy: capacity to do work ² Concept dates from mid-1800’s ² Can be converted between various forms ) Kinetic (energy of motion) ) Gravitational potential (e.g., lifting weights) ) Radiant (e.g., from sunlight) ) Heat (random molecular motion) ² Energy is often conserved ² Einstein showed energy is not always conserved: E=mc 2 , meaning that energy can be converted to mass and vice versa. The sun’s energy comes from fusion, which fuses hydrogen into helium. Helium has slightly less mass than the hydrogen used to make it. The difference goes into energy. Recognizing Heat as Energy ± Late 1700’s, American Benjamin Thompson, who had become Bavarian Count Rumford, discovered heat was not a separate substance previously called caloric (Latin root “calor”) measured in calories ± He supervised boring canon, which became so hot that water used for cooling would boil. ² Old theory: “heat” stored in metal when it was cast would be released as metal is drilled out as shavings ² Rumford observed heat being released even when drill was dull & metal not ground up. (The exception probes the rule.) ² He realized energy of drilling was converted to heat. ² Similar to making fire by rubbing two sticks together, which had been known for thousands of years. Temperature (pp. 29-30) ± Temperature measures average random energy of motion (kinetic energy) ± Gas: term coined by van Helmont, early 1600’s, from Greek word chaos. Excellent name because we now know that a gas consists of molecules in random motion ± Temperature scales (freezing, boiling) ² Fahrenheit in US (32, 212 deg F) ² Celsius everywhere else (0, 100 deg C) ± Absolute zero: -459 deg F = -273 deg C ² Lowest approachable temp ² Minimum motion Fahrenheit and Celsius F = (9/5)C + 32, C = (5/9)(F-32) deg F deg C -40 = -40 (same with both temp scales) 32 = 0 (cold) 50 = 10 (cool) 61 = 16 (digits reversed) 68 = 20 (warm) 86 = 30 (68 and 86 are reversed) (hot) 104 = 40 (04 is 40 reversed) 212 = 100 (boiling) (Similar to fig. 2.2, p. 30) calorie is a unit of energy ± calorie = energy needed to warm 1 gram of liquid water by 1 deg C ± Food Calorie (usually capitalized) = 1000 calories
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Jon Ahlquist 9/17/2006 MET1010 Intro to the Atmosphere 2 (First column of p. 30: Specific heat) Table 2.1, p. 30: calories needed to warm 1 g of substance by 1 deg C Water 1.0 Wet mud 0.6 Sandy clay 0.33 Dry air 0.24 Much energy needed to warm water, medium amount to warm ground. Little energy is needed to warm air. Consequently, marine & coastal areas don’t have extreme
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This note was uploaded on 07/21/2011 for the course MET 1010 taught by Professor Staff during the Fall '08 term at FSU.

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ch02 - Jon Ahlquist 9/17/2006 Chapter 2 Energy: Warming the...

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