Outline Chapter 5 Matter and Energy 5-1. Temperature 5-2. Heat 5-3. Metabolic Energy 5-4. Density 5-5. Pressure 5-6. Buoyancy 5-7. Gas Laws 5-8. Kinetic Theory of Gases 5-9. Molecular Motion and Temperature 5-10. Liquids and Solids 5-11. Evaporation and Boiling 5-12. Melting 5-13. Heat Engines 5-14. Thermodynamics 5-15. Fate of the Universe 5-16. Entropy 5-1. Temperature The fahrenheit scale in which water freezes at 32 F and boils at 212 F at sea level. The celsius scale in which water freezes at 0 C and boils at 100 C at sea level. C= 5/9 ( o F - 32) F= 9/5 ( o C) + 32 53 o C =? o F 127.4 o F 95 o F =? o C 35 o C 5-1. Temperature Measuring Temperature Temperature = average kinetic energy. Heat= total energy. Difference in expansion of two metals side by side Expansion of a liquid The Lake and the glass of water both are at 70 o F. Which has the most heat? A thermostat makes use of the different rates of thermal expansion in the metals of a bimetallic strip to switch heating and cooling systems on and off. 5-1. Temperature Measuring Temperature Expansion of a liquid 1
5-2. Heat The SI unit of heat is the joule as well as the calorie. James Prescott Joule (1818-1889) Heat can be transferred in three ways: 1. Conduction, in which heat is transferred from one place to another by molecular collisions. 2. Convection, in which heat is carried by the motion of a volume of hot fluid. 3. Radiation, in which heat is transferred by electromagnetic waves. 5-3. Metabolic Energy The complex of biochemical reactions that make food energy available for use by living organisms is called metabolism. A kilocalorie (4.2kj) is the amount of heat needed to change the temperature of 1 kg of water by 1 C; it is equal to one dietary "calorie." Food kcal 1 raw onion 5 1 dill pickle 15 1 gum drop 35 1 poached egg 75 1 banana 120 1 cupcake 130 1 broiled hamburger patty 150 1 glass of milk 165 1 cup bean soup 190 1 cup tuna salad 220 1 ice cream soda 325 ½ broiled chicken 350 1 lamb chop 420 5-2. Heat The heat needed to change the temperature of 1 kg of a substance by 1 C is different for different substances. 5-3. Metabolic Energy The conversion of metabolic energy into biological work is relatively inefficient; much of the energy is lost as heat. The maximum metabolic rate or power output depends on the animal s ability to dissipate heat. 5.2 W/kg 1.2 W/kg 0.67 W/kg 5-2. Heat 5-4. Density M D = ------- V Specific Heat is a measure of how much heat a substance can hold. Water holds more heat per gram than any other substance. Substance Water 4.2 Human Body 3.5 Concrete 2.9 Alcohol (ethyl) 2.4 Ice 2.1 Steam 2.0 Wood 1.8 Aluminum 0.92 Glass 0.84 Iron 0.46 Copper 0.39 Gold 0.13 Specific Heat kj/kg C o M D M = ------- D V V Find the mass of water in the bathtub above. 1000kg = ----------- (0.234 m 3 ) = 234kg 1 m 3 or 1 g/cm 3 2
5-5. Pressure F P = ------- A Fig. 5.16 The SI unit of force is the pascal: 1 pascal = 1 Pa = 1 newton/meter 2 Atmospheric pressure at sea level averages 101 kpa (equals approximately 15 lb/in 2 ). Instruments called barometers measure atmospheric pressures. Hydraulic ram converts pressure in a liquid into an applied force. The pressure is provided by an enginedriven pump. 5-5. Pressure 6-6. Buoyancy F b = dxvxg P=ρxgxdepth Pressure exerted by 60- kg woman s heel onto the floor is about 40 times the estimated pressure of the feet of a 35-ton apatosaurus on the ground. Archimedes' principle states: Buoyant force on an object in a fluid is equal to the weight of fluid displaced by the object. P = F/A = 588N/5x10-5 m 2 = 1.2x10 7 N/m 2 = 12 MPa 5-5. Pressure Measuring Blood Pressure Pump until blood flow stops. Release until hear gurgling of blood flow (systolic). Release until gurgling stops (diastolic). Normal is 120/80 torr. 5-6. Buoyancy Item Mass Volume Wood Animal 19.343g 297-277=20 ml Golf Ball 45.450g 296-250=46 ml Syringe 2.601g 211-209=2 ml Ping Pong Ball 3.444g 217-215=2 ml (only a portion is submerged) Orange Spigot 15.859g Weighing by Volume 219-204=15 ml F b = dxvxg P=ρxgxdepth You can estimate mass by measuring the volume of water an object displaces. Compare the mls the object displaces in a graduated cylinder below to the measured mass on a balance. 3
5-6. Buoyancy F b = dxvxg P=ρxgxdepth 5-7. Gas Laws Diet sodas contain no sugar and mostly water. Therefore they displace the same amount of water as in the can and they will barely float. Non-diet sodas contain sugar which gives them a density greater than water and they will sink. Boyle s Law P 1 V 2 = P 2 V 1 Charles s Law V 1 V 2 = T 1 T 2 Ideal Gas Law P 1 V 1 P 2 V 2 = T 1 T 2 Fig. 5.18 Fig. 5.38 Air at high pressure in a the tank of a scuba diver is reduced by a regulator valve to the pressure at the depth of the water. The diver must wear lead weight to overcome his or her buoyancy. The deeper the diver goes, the greater the water pressure, and the faster the air in the tank is used up. Pressure Cooker. By increasing temperature you can increase the pressure. Fig. 5.20 Fig. 5.33 Because water expands when it freezes it becomes less dense and floats. 90% of this ice berg off of Greenland is under water. The snow making machine shoots expanded mixture of ice and air to freeze to snow. 4
Absolute Zero 5-10. Liquids and Solids Absolute zero is -273 C and is the theoretical but unreachable lowest possible temperature. The intermolecular attractions between the molecules of a liquid are stronger than those in a gas but weaker than those in a solid. Molecules of a solid do not move freely about but vibrate around fixed positions. 5-8. Kinetic Theory of Gases A. Gas molecules are small compared with the average distance between them; a gas is mostly empty space. 1. Gases are easily compressed. 2. Gases are easily mixed. 3. The mass of a certain volume of gas is much smaller than that of the same volume of a liquid or a solid. B. Gas molecules collide without loss of kinetic energy. C. Gas molecules exert almost no forces on one another, except when they collide. 5-9. Molecular Motion and Temperature The absolute temperature of a gas is proportional to the average kinetic energy of its molecules. Gas molecules, even at 0 K (-273 C), would still possess a small amount of kinetic energy. Compression of a gas increases its temperature; expansion decreases its temperature. Gas molecules are in constant motion because their collisions result in no net loss of energy. Increases decreases 5-11. Evaporation and Boiling Boiling is when vapor pressure equals atmospheric pressure. http://intro.chem.okstate.edu/1314f00/laboratory/ glp.htm Sublimation is the direct conversion of a substance from the solid to the vapor state, or from the vapor state to the solid state, without it entering the liquid state. 5
5-11. Evaporation and Boiling 5-13. Heat Engines F B As These As liquid the bubbles gas is inside heated, can the only bubbles form of when expands, gas begin the the gas to inside buoyant has enough force pressure on form the bubble to overcome grows, the eventually pressure causing the liquid it to rise and to atmosphere the surface above the liquid Changes of State 5-13. Heat Engines heat of vaporization heat of fusion http://auto.howstuffworks.com/engine1.htm Changes of State How a Refrigerator Works 6
5-14. Thermodynamics Thermodynamics is the science of heat transformation. The first law of thermodynamics states: Energy cannot be created or destroyed, but it can be converted from one form to another. The second law of thermodynamics states: It is impossible to take heat from a source and change all of it to mechanical energy or work; some heat must be wasted. 5-15. Fate of the Universe 5-16. Entropy Entropy is disorder. The universe is increasing its disorder (another version of the 2 nd law of thermodynamics). The heat death of the universe will occur when all particles of matter ultimately have the same average kinetic energy and exist in a state of maximum disorder. Heat Engine Efficiency Lecture Quiz 5 Maximum efficiency of a heat engine depends on the temperatures at which it takes in and ejects heat; the greater the ratio between the two temperatures, the more efficient the engine: T cold 368 o K Efficiency = 1 - ----- = 1 - -------- = 0.56 T hot 843 o K 1. What do heat engines need to work? 2. What is the difference between heat and temperature? 3. What is room temperature in Centigrade? 4. What are the equations for density and pressure? 5. What is Entropy? Steam Engine and Electric Power Plants http://jersey.uoregon.edu/vlab/cannon/ 7
Lecture Quiz 5 Lecture Quiz 5 1. What do heat engines need to work? Hot and cold reservoir 2. What is the difference between heat and temperature? T=average KE, H=total energy 3. What is room temperature in Centigrade? 20 o C 4. What are the equations for density and pressure? D=M/V P=F/A 5. What is Entropy? Disorder 4. What are the two laws of thermodynamics? 1-Energy cannot be created or destroyed, but it can be converted from one form to another. 2-It is impossible to take heat from a source and change all of it to mechanical energy or work; some heat must be wasted or Entropy is increasing in the universe. 5. What is Entropy? The measure of disorder. Lecture Quiz 5 1. What do heat engines need to work? 2. What happens to the temperature of a material while it is melting? 3. What is the maximum efficiency of an engine when the temperature of the fluid in the radiator is 375K and the temperature of the exhaust gases is 750K? 4. What are the two laws of thermodynamics? 5. What is Entropy? Lecture Quiz 5 1. What do heat engines need to work? Hot and cold reservoir 2. What happens to the temperature of a material while it is melting? It stays the same. Energy goes into phase change. 3. What is the maximum efficiency of an engine when the temperature of the fluid in the radiator is 375K and the temperature of the exhaust gases is 750K? Efficiency = 1- T cold /T hot = 1-(375K/750k) = 0.50 = 50% 8