Chapter 27.1 NotesChapter 27.1 Notes

• I. ConductionI. Conduction

• A. DEF- the transfer of heat by the A. DEF- the transfer of heat by the direct contact of particles of matter. direct contact of particles of matter.

• 1. All objects are made of molecules. 1. All objects are made of molecules.

• 2. Collisions occur often on the 2. Collisions occur often on the molecular level.molecular level.

• 3. As temp increases, the number of 3. As temp increases, the number of collisions increases, as well. collisions increases, as well.

• 4. As the molecules of a warmer substance 4. As the molecules of a warmer substance

are combined with molecules of a cooler are combined with molecules of a cooler substance…..they eventually collide enough substance…..they eventually collide enough so that the faster molecules slow down and so that the faster molecules slow down and the slower molecules speed up.the slower molecules speed up.

• a. This is how thermal equilibrium occurs by a. This is how thermal equilibrium occurs by conduction. conduction.

• Why do we use some materials to keep Why do we use some materials to keep things warm? Ex. Down jackets, Styrofoam things warm? Ex. Down jackets, Styrofoam cups, etc?cups, etc?

• 5. Thermal Conductors-DEF-in general, 5. Thermal Conductors-DEF-in general, materials that heat easily. Ex. Metalmaterials that heat easily. Ex. Metal

• 6. Thermal Insulators-DEF- those that 6. Thermal Insulators-DEF- those that conduct heat poorly. Ex. Styrofoam.conduct heat poorly. Ex. Styrofoam.

• ( That’s why most coffee cups are made of ( That’s why most coffee cups are made of styrofoam).styrofoam).

Ch. 27.2 NotesCh. 27.2 Notes

• A. ConvectionA. Convection• 1. DEF- the transfer of heat by the actual 1. DEF- the transfer of heat by the actual

motion of a fluid (liqud or gas) in the form motion of a fluid (liqud or gas) in the form of currents. of currents.

• ( Think about holding your hands over an ( Think about holding your hands over an open flame in order to warm them up.)open flame in order to warm them up.)

• 2. Convection occurs because warmer 2. Convection occurs because warmer fluids are less dense and rise. fluids are less dense and rise.

• 3. Cooler fluids are more dense, and sink. 3. Cooler fluids are more dense, and sink. • 4. This motion ( 3 & 4) causes currents. 4. This motion ( 3 & 4) causes currents.

• B. Why does warm air rise?B. Why does warm air rise?

• 1. There is an upward force called 1. There is an upward force called buoyancy. buoyancy.

• 2. This force occurs whenever you have 2. This force occurs whenever you have an object submerged in a denser medium. an object submerged in a denser medium.

• Ex. Trying to push a ball under water. Ex. Trying to push a ball under water.

• 3. Near coastlines, convection is 3. Near coastlines, convection is responsible for sea breezes. responsible for sea breezes.

• * This is where the land is cooler than the * This is where the land is cooler than the water during the day and its possible for water during the day and its possible for the water to be cooler than the land in the the water to be cooler than the land in the evening. evening.

• C. Convection in everyday life….C. Convection in everyday life….

• 1. Cooking on a gas stove-the heat from 1. Cooking on a gas stove-the heat from the burning gas rises to heat the water in the burning gas rises to heat the water in the pan. the pan.

• 2. Wearing a sweater keeps you warm- the 2. Wearing a sweater keeps you warm- the sweater traps air in all the small pockets. sweater traps air in all the small pockets.

• 3. Wind chill- As air passes over your body 3. Wind chill- As air passes over your body is carries heat away. is carries heat away.

• * As the wind speed increases, the rate at * As the wind speed increases, the rate at which heat is carried away increases, also.which heat is carried away increases, also.

• 4. Chimneys- convection forces the heat to 4. Chimneys- convection forces the heat to go up by rising hot air. go up by rising hot air.

• D. Forced convectionD. Forced convection

• 1. DEF- a mechanical device is used to 1. DEF- a mechanical device is used to force the fluid or gas to move. ( * as force the fluid or gas to move. ( * as opposed to buoyant force.*)opposed to buoyant force.*)

• 2. Most often times, a fan or pump is 2. Most often times, a fan or pump is used. used.

• 3. Common examples:3. Common examples:

• a. Radiator in a cara. Radiator in a car

• b. Radiator heater in a houseb. Radiator heater in a house

• c. Air conditioner- cool air is blown through c. Air conditioner- cool air is blown through a room with a fan. The forces the cooler a room with a fan. The forces the cooler air to replace the warmer air. air to replace the warmer air.

Ch. 27.3 NotesCh. 27.3 Notes

• A. Radiation A. Radiation

• 1. DEF- heat transfer that does not require 1. DEF- heat transfer that does not require matter to travel through. matter to travel through.

• * Remember, sound had to have a medium * Remember, sound had to have a medium to travel through in order to hear it. to travel through in order to hear it. Radiation can travel without a medium- so Radiation can travel without a medium- so it can travel in space. Also, both it can travel in space. Also, both conduction and convection require matter conduction and convection require matter to transfer heat. to transfer heat.

• 2. The Earth receives most of its 2. The Earth receives most of its heat from the sun. heat from the sun.

• a. The sun gives off electromagnetic a. The sun gives off electromagnetic radiation and it is able to reach the radiation and it is able to reach the earth because radiation can travel in earth because radiation can travel in space- which is a vaccum. ( sound space- which is a vaccum. ( sound cant..)cant..)

• 3. Infrared radiation- this has lower 3. Infrared radiation- this has lower energy than visible light. energy than visible light.

• a. Humans cannot detect this but a. Humans cannot detect this but certain snakes can. certain snakes can.

•Where does solar radiation Where does solar radiation

go?go?• 30 % is returned to outer space. 30 % is returned to outer space.

• 47 % is absorbed by the Earth.47 % is absorbed by the Earth.

• 23 is used to drive the 23 is used to drive the hydrologic cycle. hydrologic cycle.

• .2 % drives the winds.2 % drives the winds

• .02 % is absorbed by plants for .02 % is absorbed by plants for photosynthesis. photosynthesis.

• B. Absorption and EmissionB. Absorption and Emission• 1. Reflectors-DEF- objects that reflect 1. Reflectors-DEF- objects that reflect

most of the radiation that hits the object. most of the radiation that hits the object. • a. Ex. Shiny metallic objects, white objectsa. Ex. Shiny metallic objects, white objects• * Think about a bike reflector.* Think about a bike reflector.• 2. Absorbers- objects that absorb the 2. Absorbers- objects that absorb the

radiation that hits the object. radiation that hits the object. • a. Ex. Black objects- road pavement, solar a. Ex. Black objects- road pavement, solar

panelspanels• 3. Most objects that are good absorbers 3. Most objects that are good absorbers

are also good emitters of heat. are also good emitters of heat. • a. compare the beach sand vs. pavement. a. compare the beach sand vs. pavement.

• C. PlanetsC. Planets

• 1. Planets and our moon reflect the sun’s 1. Planets and our moon reflect the sun’s light. light.

• ( Stars are the only thing besides the sun ( Stars are the only thing besides the sun that actually produce their own light. )that actually produce their own light. )

• 2. Albedo- the percentage of the sun’s light 2. Albedo- the percentage of the sun’s light reflected from its surface. reflected from its surface.

• a. Planets with high albedo’s-Venus, Jupiter a. Planets with high albedo’s-Venus, Jupiter and Saturn (because they have a lot of and Saturn (because they have a lot of clouds. )clouds. )

• b. Low Albedo Planets- Mercury and our b. Low Albedo Planets- Mercury and our moon- because they have very little moon- because they have very little atmosphere. atmosphere.