Transcript Chapter 5
Chapter 16 Thermal Energy and Matter Work and Heat Doing work on something can cause a material to heat up. Heat The flow of Thermal Energy. Heat is the flow of Thermal Energy from an area of High Temperature to one of Low Temperature. Temperature and Heat Temperature: The measure of the average kinetic energy of the particles in a sample of matter. Kinetic Theory Of Matter Thermal Energy The total energy, potential and kinetic, of the particles in a material. •Temperature •Mass •Phase •Solid •Liquid •Gas Thermal Energy The total energy, potential and kinetic, of the particles in a material. 1g 25ºC 1kg 25ºC Phase 1kg 0°C 1kg 0°C Phase 1kg 1kg 0°C 100°C 1kg 100°C Thermal Contraction and Expansion Thermal Contraction and Expansion Thermal Contraction and Expansion Temperature Increase - Faster Decrease - Slower What expands more?? Solids Least!!! Greatest force between particles! Liquids More!!! Less force between particles! Gas Most!!! No forces between particles! Measuring Thermal Energy Type of Material (phase) Mass of Material Temperature Material Water Metal Specific Heat Specific Heat [C, J / (kg • K)] The amount of energy it takes to it takes to raise the temperature of 1 kg of material 1 Kelvin. ( K = C ) It takes 4184 joules of energy to raise the temperature of 1 kg of water, 1C. Material Water Alcohol Aluminum Graphite(Carbon) Sand Iron Copper Silver Specific Heat 4184 2450 920 710 664 450 380 235 J / (kg • K) J / (kg • K) J / (kg • K) J / (kg • K) J / (kg • K) J / (kg • K) J / (kg • K) J / (kg • K) Calculating Thermal Changes Change in Thermal Energy - Q Mass - m Change in Temperature - T Specific Heat - C Q = m • T • C T = Tfinal - Tinitial Example: Mr. Clune wants to bring 1 kg of water to boiling for his afternoon tea. The temperature of the water out of the tap is 10C. How much Thermal Energy does he have to add to the water? Given: m = 1 kg Find: Q = ? Tinitial = 10C Tfinal = 100C C = 4184 (J / (kg • C ) ) Equation: Q = m • T • C Q = m • (Tfinal - Tinitial) • C Solve: Q = (1 kg) • (100C -10C) • 4184(J/(kg • C) Q = (1 kg) • (90C) • 4184 (J/(kg • C) Q = 377,000 J or 377 kJ Example: Do the same problem as the one above but use sand instead. Given: m = 1 kg Find: Q = ? Tinitial = 10C Tfinal = 100C C = 664 (J / (kg • C ) ) Equation: Q = m • T • C Q = m • (Tfinal - Tinitial) • C Solve: Q = (1 kg) · (100C -10C) · 664(J/(kg.C) Q = 60,000 J or 60 kJ Calorimeter Measuring Heat Changes Homework 16-1 16.1- Worksheet Bookwork Page:477 Problems: 1-5 Due: 4/29/08 Heat and Thermodynamics Heat Thermal Energy Transfer: Thermal Energy is transferred in three ways: Conduction Convection Radiation Conduction In conduction energy is transferred through matter from particle to particle. OUCH!!!! In which is fastest?? Liquid Solid Gas Particles are closer together!! Thermal Conductor A material that conducts thermal energy well. Thermal Insulator A material that conducts thermal energy poorly. Convection The transfer of thermal energy by the movement of matter. Convection is the most important method of transferring thermal energy in a fluid. ( fluids - liquids or gasses ) Radiation The transfer of energy that does not require matter. Reducing Thermal-Energy Flow Insulation: reduces the flow of thermal energy. Conduction Convection Radiation R-Value Measure of the effectiveness a material as an insulator. “R” stands for resistance to heat flow. Material Brick Wood Siding Air Space Fiberglass Aluminum Siding R-value 0.08/cm 0.60/cm 2.00/cm 1.22/cm 0.01/cm Highest R Value Thermodynamics Thermodynamics is the study of the conversion of thermal energy into other forms of energy. First Law of Thermodynamics Energy is Conserved!!! Second Law of Thermodynamics Energy can flow from colder objects to hotter objects only if work is done. Third Law of Thermodynamics Absolute Zero cannot be reached. Homework: 16-2 Worksheet: 16.2 Due: 5/1/08 Test: 5/8/08 External Combustion Engine: Fuel is burned outside the engine. Old Fashion Steam Engine Heat Engines Internal Combustion Engine: The burning of fuel, usually gasoline or diesel, inside an engine. ( Gas - 12% efficient, Diesel - 25% efficient ) Two Cycle Engine Four Stroke Engine Four Cycle Engine Air Diesel Heating Systems Radiator Water or Steam Forced-Air System Cool Air Hot Air Electric Heating System Window Heating Element Heat Movers A machine that removes heat from an object at low temperature and gives it to one at a high temperature. Refrigerator Air Conditioner Gas Absorbs Heat!! Compressor Liquid Heat!! Gas Expansion Valve Heat Pump A heat mover that can work in both directions. In the summer it acts as an ordinary air conditioner. In the winter it removes thermal energy from the outside air or ground at a low temperature and delivers it inside at a higher temperature. Heat Pump Homework Worksheet: 16.3 Word-wise Math Due: 5/7/08 Test: 5/8/08 Sweat - The Human Coolant Solar Heating Solar Energy: Energy from the sun. Passive Solar Heating Passive Solar Systems: Uses no fans or mechanical devices to transfer heat from one area to another. Materials in the system absorb radiant energy during the day, convert it to thermal energy, and radiate the thermal energy after dark. Passive Solar Heating Heat Storage Active Solar Heating Active Solar Heating: The radiant energy is absorbed using solar collectors by heating up water or air which is then pumped through the house. Active Solar Heating Solar Collector Online Homework: 6-2 Worksheet Section Wrap-up Page: 165 Due: 11/30/05 Homework: 6-3 Worksheet Section Wrap-up Page: 170 Due: 12/6/05 Energy from the Ocean Ocean Thermal Energy Conversion OTEC The process that uses heat engines to convert differencess in ocean water temperature into mechanical energy to drive turbines. Turbine Warm Water Evaporator Condenser Cold Water Pump Fusion