Energy. Energy (E) is the ability to do work. Many types, but we can say 3 main types: Radiant Potential Kinetic

Transcription

1 ENERGY

2 Energy n n n Energy (E) is the ability to do work. Many types, but we can say 3 main types: Radiant Potential Kinetic

3 US Energy Consumption by Source

4 Light Energy Visible and Invisible Radiant Energy Travels in waves over distances Electromagnetic waves nwaves that spread out in all directions from the source nvisible light, UV light, Infra Red Radiation, X-rays, microwaves, radio waves

5 Potential Energy (PE) Stored Energy Due to position ngravitational PE nelastic PE Chemical bonds nchemical PE n Nuclear energy nfuels nattractions between molecules

6 Energy of motion Atomic vibrations Molecular movement nvibration nrotation n Translation Movement of subatomic particles Kinetic Energy (KE)

7 Kinetic Energy Can be calculated:

8 How are each type shown here?

9 How are each type shown here? Radiant Rainbow = visible light Kinetic Windmill moving Potential All molecules store energy n Water in clouds n Air n Materials the windmill is made from, the plants at the bottom

10 Where is the PE? KE?

11 Temperature Scales: Measuring that Thermal Energy Boiling Freezing Fahrenheit ( o F) Celsius ( o C) Kelvin

12 A Note on the Fahrenheit Scale NEVER use it in this class. Ever. Only Belize and the US use this scale. Gabriel Fahrenheit made great thermometers. His scale was replicated the world over because of this. But if you stop and think about it, does 32 F for freezing make sense, or 212 F for boiling? 180 degrees separates them. 100 degrees, as in the Celcius scale (sometimes called the Centigrade scale) makes much more sense. Fahrenheit based 0 F on the freezing point of water mixed with NH 4 Cl, and 32 F for freezing water, and 96 F for human body temperature (he was off by 2.6 ). Why? Because he felt like it and it was easy to draw lines at those intervals. (According to a letter Fahrenheit wrote to his friend Herman Boerhaave, [8] his scale was built on the work of Ole Rømer, whom he had met earlier. In Rømer s scale, brine freezes at 0 degrees, ice melts at 7.5 degrees, body temperature is 22.5, and water boils at 60 degrees. Fahrenheit multiplied each value by four in order to eliminate fractions and increase the granularity of the scale. He then re-calibrated his scale using the melting point of ice and normal human body temperature (which were at 30 and 90 degrees); he adjusted the scale so that the melting point of ice would be 32 degrees and body temperature 96 degrees, so that 64 intervals would separate the two, allowing him to mark degree lines on his instruments by simply bisecting the interval six times (since 64 is 2 to the sixth power). I took this from Wikipedia.

13 Kelvin Temperatures Based on absolute zero (0 K, -273 o C) The temperature at which ALL KE stops NO molecular motion. Lowest temperature theoretically possible ncan t really get there in real life n(see 3 rd Law of Thermodynamics in a few slides) K = o C Technically , but we can stop at 3 significant digits

14 Why do we need the Kelvin scale? Two reasons We need a scale that is relative to molecular motion for certain topics n You can t use negative numbers to indicate motion when it IS present n -20 C makes NO sense in light of indicating motion n And 40 C ISN T twice as much motion as 20 C, n (40K IS twice the motion of 20K) Because when working with equations, can t use zero n We get undefined answers if we divide n We get answers of 0 if we multiple n And those answers would NOT make sense if compared to answers calculated with a positive or negative number

15 The 4 Es: Energy, Exergy, Entropy, & Enthalpy Energy (E): The ability to do work Entropy (S): The measure of the disorder of a system Exergy: The energy available to do work No symbol Enthalpy(H): The thermal energy (heat) content of a system There will be more on these!

16 Radiant Energy: EM Waves Potential Energy: Stored Kinetic Energy: Motion

17 The CPE in these items could:

18 Combinations of PE and KE are very common on a large scale KE and PE animation

19 PE and KE

20 When E changes forms The amount of energy one thing loses is gained somewhere else. E lost = E gained (Law of Conservation of Energy) But the E gained is usually not all in one place (2 nd Law of thermodynamics) nit is spread out (more entropy) noften in the forms of heat and light n Which are less useful (less exergy)

21 Energy Transformations

22 Exothermic and Endothermic Processes Endothermic Energy is being gained/ absorbed by the object or substance (called the system) from the surroundings Exothermic Energy is lost/ released from the object or substance (called the system) to the surroundings

23 Exothermic Reactions? I studied them before they were cool.

24 Which is process is endothermic? Which is exothermic?

25 The big picture How do we see this energy cycling in the real world, and not just as a part of Chemistry class? Around the house? In the environment?

26 Trophic Levels and Energy Consumers are all heterotrophs 3 Consumers: Carnivores and Omnivores 2 Consumers: Carnivores and Omnimores Energy Out; 90% per level 1 Consumers: Herbivores Producers: Autotrophs

27 Trophic Levels and Energy 3 Consumers 2 Consumers 1 Consumers While this shows only a 1 consumer, all animals lose E the same way; high levels lose more to motion than do lower levels

28 Trophic Levels and Energy

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31 Class Question: How does a car exhibit all types of energy? Explain!

32 Energy Loss in a Car

33 Can the world really run out of Energy? World-Wide Energy Sources, (2007)

34 PHASE CHANGES & ENERGY

35 Phase Diagrams

36 A few terms Vaporization - The conversion of a liquid to a gas or vapor Evaporation - When vaporization occurs at the surface of a liquid that is not boiling Most of the molecules in a liquid don t have enough kinetic energy to overcome the attractive forces and escape into the gaseous state. Some of the particles that do escape collide with molecules in the air and rebound back into the liquid.

37 One more term: Vapor Pressure Measures the force exerted by a gas above a liquid in a sealed container Over time, the number of particles entering the vapor increases and some of the particles condense and return to the liquid state. Eventually, the number of particles condensing will equal the number of particles vaporizing. The vapor pressure will then remain constant. This is known as equilibrium because the rate of evaporation of liquid equals the rate of condensation of vapor. So Vapor Pressure - The pressure at which the vaporization rates are equal to condensation rates

38 Measuring Vapor Pressure

39 Still more terms Boiling Point - The temperature at which the vapor pressure of a liquid is equal to the external pressure on the liquid. Because a liquid boils when its vapor pressure is equal to the external pressure, liquids don t always boil at the same temperature. A change in altitude affects the boiling point of water. Because atmospheric pressure is lower at higher altitudes, boiling points decrease at higher altitudes. Freezing Point - The temperature at which a liquid changes to a solid Melting Point - The temperature at which a solid changes to a liquid Both are at the same temperature

40 A few more terms Sublimation The change of a substance from a solid to a vapor without passing through the liquid state Sublimation can occur because solids have a vapor pressure. Occurs in solids with vapor pressures that exceed atmospheric pressure at or near room temperature. Deposition - The change of a substance from a gas to a solid without passing through the liquid state

41 Phase Diagrams Tell what state of matter a material is in at a given temperature and pressure The triple point is the pressure and temperature when a solid, liquid, and a gas of the same substance exist at equilibrium Equilibrium: When there is no net change n Here referring to changes in state n Can also refer to temperature and chemicals The critical point is the temperature above which a substance will always be a gas, regardless of pressure Fullerton Phase Diagram Explorer Link

42 Phase Diagrams

43 Phase Diagram for Water

44 Energy and Phase Changes

45 Energy and Matter and Connected Any change in matter ALWAYS is accompanied by a change in energy