ENERGY. Reading: Supplemental Text Materials Chapter 11: pages

Transcription

1 ENERGY Reading: Supplemental Text Materials Chapter 11: pages

2 Energy Ability to do work Unit: Joule (J) J = (kg x m 2 )/s 2

3 Power Energy over time Watts (W) 1 W = 1J/s

4 Power is energy over time

5 Types of Energy Mechanical Electrical Chemical Radiant (Light) Heat Nuclear

6 Mechanical Energy Potential Energy Kinetic Energy

7 Stored energy Potential Energy

8 Kinetic Energy Energy of motion

9 Energy Conversion From high-grade to lower-grade forms

10 Energy conversion Mechanical to Electrical

11 Energy conversion Chemical to mechanical

12 Energy conversion Radiant to heat Radiant to electrical

13 Steam Turbine

14 Earth s Energy Sun 99+% of Earth s energy Internal heat radioactive decay gravitational pressure

15 Sun s Energy Radiant energy Released by fusion Hydrogen fused into Helium 1.73 x watts received by Earth from Sun Converted by plants into chemical energy

16 Photosynthesis 6 CO H 2 O sun energy C 6 H 12 O 6 + O 2 Converts CO 2 and H 2 O to sugar and O 2 Created the level of oxygen present in today s atmosphere Ancient algae in Archean and Proterozoic oceans released O 2 by photosynthesis

17 Source of energy not from Sun Rare deep sea vent communities Sulfurous hotsprings supports bacteria Other organisms subsist on bacteria Larger creatures can survive on the bacteria-eating organisms

18 Black Smoker

19 Vent community

20 Tube worm and crab

21 Energy and Chemical Reactions Temperature affects rate of reactions More molecule collisions More energy to break chemical bonds Concentration of reactants Presence of catalyst Peroxide 2 H 2 O 2 2 H 2 O + O 2 proceeds slowly Add platinum: takes seconds, not years

22 Energy and Chemical Reactions Heat released or consumed in chemical reactions Measured in calories Food calorie is a kilocalorie (kcal) 1 Joule = 0.24 calories Energy shown in equation C 3 H O 2 3 CO H 2 O kcal

23 Reaction energy EXOTHERMIC heats up environment ENDOTHERMIC absorbs heat from environment

24 Exothermic Reaction C 3 H O 2 3 CO H 2 O kcal Burn 2 moles of propane 2 x 526 kcal = 1052 kcal Burn 308 g of propane 308 g (1 mole/44g) = 7 moles 7 moles x 526 kcal = 3682 kcal

25 Endothermic reaction N 2 + O kcal 2 NO 5 moles of nitrogen, reacting with 5 moles of oxygen Consumes 5 x 4.32 kcal = 21.6 kcal

26 Conservation of Energy Energy is not created or destroyed First Law of Thermodynamics

27 Heat Flow From objects with heat to those with less Change form from high quality to lower quality Chemical to heat friction

28 Entropy Lack of order of systems Nature tends toward disorder greater entropy Takes energy to overcome entropy Oil spill on Columbia River CFC released into atmosphere

29 Energy sources Wood chemical energy stored by plants Kinetic energy Water power to grind grain Wind to pump water Fossil fuels

30 Fossil fuels Burn readily Reaction is oxidation Release heat energy

31 Fossil fuels Coal Petroleum Natural Gas

32 First law of thermodynamics Conservation of energy Cannot create or destroy energy (But we can convert to less-useful form)

33 Fossil fuels Non renewable From ancient organisms Extracted from Earth

34 Coal C + O 2 CO 2 Anthracite Bitumen Lignite

35 Coal Incompletely decayed plants Burial pressure releases O 2 and H 2 Carbon remains Paleozoic Pennsylvanian coal, Carboniferous Era

36 Carboniferous Period Forest

37 Coal formation 1

38 Coal formation 2

39 Coal formation 3

40 Coal formation 4

41 Coal formation Summary

42 Coal Must be mined Pollutants in coal Sulfur leads to acid rain Also contains mercury, arsenic, nitrates

43 Coal Coke is made by heating coal Byproduct refined into organic chemicals

44 Natural Gas Mostly methane CH O 2 CO H 2 O + heat Excellent, clean-burning fuel Raw material for plastics and other chemicals

45 Petroleum Replaced coal by about 1950 Complex hydrocarbon molecules Derived from fats Combustion products are carbon dioxide and water

46 Petroleum C 8 H O 2 16 CO H 2 O Also contains some sulfur compounds Fuel oil is fairly clean Burning gasoline results in smog Internal combustion engines inefficient