Chapter 27.1 Notes I. Conduction I. Conduction A. DEF- the transfer of heat by the direct contact of particles of matter. A. DEF- the transfer of heat by the 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 molecular level. 2. Collisions occur often on the molecular level. 3. As temp increases, the number of collisions increases, as well. 3. As temp increases, the number of collisions increases, as well.

4. As the molecules of a warmer substance are combined with molecules of a cooler substance…..they eventually collide enough so that the faster molecules slow down and the slower molecules speed up. 4. As the molecules of a warmer substance are combined with molecules of a cooler substance…..they eventually collide enough so that the faster molecules slow down and the slower molecules speed up. a. This is how thermal equilibrium occurs by conduction. a. This is how thermal equilibrium occurs by conduction. Why do we use some materials to keep things warm? Ex. Down jackets, Styrofoam cups, etc? Why do we use some materials to keep things warm? Ex. Down jackets, Styrofoam cups, etc? 5. Thermal Conductors-DEF-in general, materials that heat easily. Ex. Metal 5. Thermal Conductors-DEF-in general, materials that heat easily. Ex. Metal 6. Thermal Insulators-DEF- those that conduct heat poorly. Ex. Styrofoam. 6. Thermal Insulators-DEF- those that conduct heat poorly. Ex. Styrofoam. ( That’s why most coffee cups are made of styrofoam). ( That’s why most coffee cups are made of styrofoam).

Ch Notes A. Convection A. Convection 1. DEF- the transfer of heat by the actual motion of a fluid (liqud or gas) in the form of currents. 1. DEF- the transfer of heat by the actual motion of a fluid (liqud or gas) in the form of currents. ( Think about holding your hands over an open flame in order to warm them up.) ( Think about holding your hands over an open flame in order to warm them up.) 2. Convection occurs because warmer fluids are less dense and rise. 2. Convection occurs because warmer 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 buoyancy. 1. There is an upward force called buoyancy. 2. This force occurs whenever you have an object submerged in a denser medium. 2. This force occurs whenever you have 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 responsible for sea breezes. 3. Near coastlines, convection is responsible for sea breezes. * This is where the land is cooler than the water during the day and its possible for the water to be cooler than the land in the evening. * This is where the land is cooler than the water during the day and its possible for the water to be cooler than the land in the evening.

C. Convection in everyday life…. C. Convection in everyday life…. 1. Cooking on a gas stove-the heat from the burning gas rises to heat the water in the pan. 1. Cooking on a gas stove-the heat from the burning gas rises to heat the water in the pan. 2. Wearing a sweater keeps you warm- the sweater traps air in all the small pockets. 2. Wearing a sweater keeps you warm- the sweater traps air in all the small pockets. 3. Wind chill- As air passes over your body is carries heat away. 3. Wind chill- As air passes over your body is carries heat away. * As the wind speed increases, the rate at which heat is carried away increases, also. * As the wind speed increases, the rate at which heat is carried away increases, also. 4. Chimneys- convection forces the heat to go up by rising hot air. 4. Chimneys- convection forces the heat to go up by rising hot air.

D. Forced convection D. Forced convection 1. DEF- a mechanical device is used to force the fluid or gas to move. ( * as opposed to buoyant force.*) 1. DEF- a mechanical device is used to force the fluid or gas to move. ( * as opposed to buoyant force.*) 2. Most often times, a fan or pump is used. 2. Most often times, a fan or pump is used. 3. Common examples: 3. Common examples: a. Radiator in a car a. Radiator in a car b. Radiator heater in a house b. Radiator heater in a house c. Air conditioner- cool air is blown through a room with a fan. The forces the cooler air to replace the warmer air. c. Air conditioner- cool air is blown through a room with a fan. The forces the cooler air to replace the warmer air.

Ch Notes A. Radiation A. Radiation 1. DEF- heat transfer that does not require matter to travel through. 1. DEF- heat transfer that does not require matter to travel through. * Remember, sound had to have a medium to travel through in order to hear it. Radiation can travel without a medium- so it can travel in space. Also, both conduction and convection require matter to transfer heat. * Remember, sound had to have a medium to travel through in order to hear it. Radiation can travel without a medium- so it can travel in space. Also, both conduction and convection require matter to transfer heat.

2. The Earth receives most of its heat from the sun. 2. The Earth receives most of its heat from the sun. a. The sun gives off electromagnetic radiation and it is able to reach the earth because radiation can travel in space- which is a vaccum. ( sound cant..) a. The sun gives off electromagnetic radiation and it is able to reach the earth because radiation can travel in space- which is a vaccum. ( sound cant..) 3. Infrared radiation- this has lower energy than visible light. 3. Infrared radiation- this has lower energy than visible light. a. Humans cannot detect this but certain snakes can. a. Humans cannot detect this but certain snakes can.

Where does solar radiation go? Where does solar radiation 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 hydrologic cycle. 23 is used to drive the hydrologic cycle..2 % drives the winds.2 % drives the winds.02 % is absorbed by plants for photosynthesis..02 % is absorbed by plants for photosynthesis.

B. Absorption and Emission B. Absorption and Emission 1. Reflectors-DEF- objects that reflect most of the radiation that hits the object. 1. Reflectors-DEF- objects that reflect most of the radiation that hits the object. a. Ex. Shiny metallic objects, white objects a. Ex. Shiny metallic objects, white objects * Think about a bike reflector. * Think about a bike reflector. 2. Absorbers- objects that absorb the radiation that hits the object. 2. Absorbers- objects that absorb the radiation that hits the object. a. Ex. Black objects- road pavement, solar panels a. Ex. Black objects- road pavement, solar panels 3. Most objects that are good absorbers are also good emitters of heat. 3. Most objects that are good absorbers are also good emitters of heat. a. compare the beach sand vs. pavement. a. compare the beach sand vs. pavement.

C. Planets C. Planets 1. Planets and our moon reflect the sun’s light. 1. Planets and our moon reflect the sun’s light. ( Stars are the only thing besides the sun that actually produce their own light. ) ( Stars are the only thing besides the sun that actually produce their own light. ) 2. Albedo- the percentage of the sun’s light reflected from its surface. 2. Albedo- the percentage of the sun’s light reflected from its surface. a. Planets with high albedo’s-Venus, Jupiter and Saturn (because they have a lot of clouds. ) a. Planets with high albedo’s-Venus, Jupiter and Saturn (because they have a lot of clouds. ) b. Low Albedo Planets- Mercury and our moon- because they have very little atmosphere. b. Low Albedo Planets- Mercury and our moon- because they have very little atmosphere.