Pretest - Chapter 16 1. What kind of energy is released when bonds are broken? 2. True or false: Thermal energy is the total potential and kinetic energy of the microscopic particles in an object. 3. What is a thermal insulator? 4. What are three types of heat transfer? 5. In what direction does heat flow?

16.1 Thermal Energy and Matter 1. What is Temperature? A measure of how hot or cold something is Measured in Celsius, Fahrenheit, Kelvin

Related to the average kinetic energy Related to the average kinetic energy (1/2mv2) of particles in an object (solid, liquid or gas), NOT the kinetic energy of the whole object http://tre.ngfl.gov.uk/uploads/materials/19383/convection.swf Card game

Depends on mass and temperature 2. What is Thermal Energy? The total potential and kinetic energy of all the particles in an object Depends on mass and temperature Temp & Therm http://jersey.uoregon.edu/vlab/Thermodynamics/therm1b.html

Heat flows from hot to cold objects 3. What is Heat? Transfer of thermal energy from one object to another due to a temperature difference Heat flows from hot to cold objects “when a group of fast-moving (warmer) molecules is placed next to a group of slow-moving (cooler) molecules, random collisions will cause the slower molecules to speed up and the faster ones to slow down, thus transferring energy from the warmer group to the cooler group” 4. Work and heat Work creates heat through friction http://phet-web.colorado.edu/web-pages/simulations-base.html http://phet.colorado.edu/en/simulation/gas-properties Thermal paper

5. What is Thermal Expansion? As temperature increases, particles of matter move faster and further apart (more energy) Thermal energy can do mechanical work Some substances expand more than others Thermometers use alcohol or mercury which expand a lot and expand consistently Ball & loop, bimetallic wand, egg

Thermostats use bimetallic strips and “measure” the Thermostats use bimetallic strips and “measure” the bend due to unequal expansion As temperature decreases, particles of matter move slower and get closer together Explain demos

Ex. Plastic vs. metal buckle on seat belt 6. What is Specific Heat? The amount of heat needed to raise the temperature of one gram of material one degree Celsius Objects with a low specific heat change in temperature MORE EASILY when given a certain amount of energy Ex. Plastic vs. metal buckle on seat belt Q = m x c x ∆T Q = thermal energy (J) First 3 problems

7. How do you measure heat changes? Use a calorimeter Thermal energy released by a test sample is equal to the thermal energy gained by surroundings. Q(lost) = Q(gained) Use surroundings whose specific heat is known (I.e. water) msample x csample x ∆Tsample = mwater x cwater x ∆Twater Next 2 problems, specific heat lab

16.2 Heat and Thermodynamics wand, balloon, ice, tea bag 16.2 Heat and Thermodynamics 1. How is thermal energy transferred? A. Conduction Transfer of thermal energy through collisions Slow in gases because there are fewer collisions Thermal conductor = a material that conducts thermal energy well (ex. Metals) Thermal insulator = a material that doesn’t conduct thermal energy well (ex. air, wood) Newton’s cradle, explain demos

When fluids heat, they expand, become less dense, and rise B. Convection Transfer of thermal energy when particles of a fluid (gas or liquid)move from one place to another When fluids heat, they expand, become less dense, and rise Convection currents are important in many natural cycles - ocean, weather, Earth’s interior Explain demo

C. Radiation Transfer of energy by waves moving through space, NO PARTICLES needed The shorter the wavelength, the more energy The radiation comes from vibrating electrons in every atom All objects radiate energy

Radiation can be: A. Absorbed: increasing the internal energy of the object (black vs. white color) B. Reflected: bouncing off an object (shiny vs. dull) C. Scattered: deflecting in all directions D. Transmitted: going through an object (transparent vs. opaque)

Heat Transfer Activity, Greenhouse, Radiometer Challenge

2. What is thermodynamics? The study of conversions between thermal energy and other forms A. First law of thermodynamics Energy is conserved B. Second law of thermodynamics Disorder (entropy) naturally increases Work must be done to make things orderly Thermal energy flows naturally from hot to cold Heat engine = any device that converts heat into work

Efficiency of an engine is less than 100% Thermal energy that is not converted to work is called “waste heat” C. Third law of thermodynamics Absolute zero cannot be reached

16.3 Using Heat

1. What are two kinds of heat engines? 16.3 Using Heat 1. What are two kinds of heat engines? A. External combustion engine An engine that burns fuel outside the engine (ex. steam engine) Hot steam enters the cylinder and pushes the piston down Heat is converted to work Some “waste” energy is lost due to friction, etc. The less waste energy, the more efficient the engine. http://travel.howstuffworks.com/steam1.htm

Basic steam engine components (locomotive… choo choo train)

B. Internal combustion engine http://auto.howstuffworks.com/engine1.htm B. Internal combustion engine An engine in which the fuel burns inside the engine (ex. Car) Air and gas enters Piston compresses Spark plug ignites Exhaust leaves

Turbine engine (internal combustion) How a turbine works

Jet engine

Steam Power Plant

Steam Power Plant Use this to guide students. Solutions on next slides.

Steam Power Plant

Nuclear Reactor basics

2. What are various heating systems? Central heating heats many rooms from one central location Use electricity, natural gas, oil, or coal Vary in how the heat gets to the rooms Use convection to distribute heat in the rooms A. Hot-water heating A boiler heats water A pump carries the water to radiators Radiators transfer heat to air by conduction and radiation Hot air sets up a convection current in the room

B. Steam heating Similar to hot water except steam is used C. Electric baseboard heating A coil of wire carries electricity The heat of the coil heats air by conduction and radiation Convection circulates the air through the room

D. Forced-air heating Furnace burns oil or gas Air is heated through conduction and radiation Fans circulate warm air through ducts Convection circulates air in each room

3. How do cooling systems work? Heat pumps reverse normal flow of thermal energy by using a refrigerant Animation of a Heat PumpThe Heat Pump A refrigerant absorbs heat and vaporizes (liquid to gas) then condenses (gas to liquid) and releases the heat elsewhere. Refrigerant are CONTAINED inside piping.

A. Refrigerator A motor moves refrigerant through tubing inside refrigerator The refrigerant removes heat from inside and vaporizes The refrigerant moves to the coils outside the refrigerator A pump pressurizes the refrigerant and forces it to condense, giving off the heat to the room

How A refrigerator works

B. Air Conditioner Tubing with liquid refrigerant absorbs heat from the air in the room and vaporizes The cool air is forced through the house The vaporized refrigerant is pumped outside A compressor forces the refrigerant to condense giving off heat to the outside