Transcript Chapter 5
Heat Transfer Friction Resistance, takes place when two objects rub together Brownian Motion The jiggling motion that particles do Robert Brownian was the first to realize this Particles are constantly moving and vibrating Movement is caused by the collision of particles Heat Heat is also known as thermal energy Kinetic energy is the form of energy associated with movement, it measures how much energy of motion particles have Temperature is the average kinetic energy of all particles in an object Heat is the sum of the kinetic energies of all particles in an object See page 86 Temperature vs. Thermal Energy Temperature = A measure of the average energy of the particles in a material. Thermal Energy/Heat = The total energy of all the particles in a material. What is the difference?? Transferring Energy There are 3 main ways to transfer energy 1) Radiation 2) Conduction 3) Convection Heat Transfer Heat flows from a hot to a cold object until they are at the same temperature Conduction is the transfer of heat via contact When you place a cool pot on a hot stove, the particles of the stove have more kinetic energy than the particles of the pot. When the two contact each other, the hot stove looses kinetic energy to the pot. The better the conductor, the more rapidly heat will transfer. Convection is the up and down movement of gases and liquids caused by heat transfer. Hot air/liquids are less dense, and cold air/liquids are more dense which creates convection current. Radiation is produced by wave that travel through space. When the waves come in contact with an object, the waves transfer the heat to that object. Convection and Weather Cottages are often located along lake shores because the air is cooler during the day and warmer at night At night, the air over the water cools slower then the air over land Warm air then moves from over the water to over land, keeping the temperature warm During the day cool air from the water moves toward the land, lowering the temperature on land Sea and Land Breezes Warm air rises, cool air sinks All winds start via convection currents Land and sea breezes start near a shoreline The suns rays are absorbed by the sea and the land at different rates, water heats slowly and takes longer to cool than air Page 94 diagrams Oceans and Climates Oceans store thermal (heat) energy Areas around oceans usually do not experience extreme weather changes In cool weather oceans release heat, while the ocean temperature remain relatively constant When the air is warm, warm air flows into the water, warming the water When the air is cool, heat flows from the ocean to the air, warming the air How Oceans Affect Climate Activity Climate Pattern Statistics for Five Canadian Cities City Mean January Temperature in Celsius Mean July Temperature in Celsius Calgary, Alberta -11 17 Quebec city, Quebec -12 19 Winnipeg, Manitoba -18 20 Regina, Saskatchewan -17 19 Vancouver, British Columbia 2 17 Graph Mean Temperature in Celsius City Ticket out the DOOR Convection happens because… a) Hot atoms are lighter than cold atoms, so cold atoms rise. b) Fluids become less dense as they are heated, and c) d) a) b) c) d) differences in density cause currents. Hot atoms rise to the top of all solid materials. Radiation cannot be absorbed or emitted by some objects. Water touching the bottom of the hot pan begins to heat up; this is an example of ? Conduction Convection Radiation None of the above Heat Transfer Materials in your home are designed to transfer heat or prevent the transfer of heat Pots facilitate transfer, where as insulation prevents it When an oven is turned on convection currents move heat As oven walls get hot, heat is radiated around the oven Getting Rid of Heat Page 101, how does heat transfer in a refrigerator work?