Chapter 6 Controlling Heat Transfer 6.1 Absorbing and Losing Heat Science 14 and 10-4 with Mrs. M.
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Transcript of Chapter 6 Controlling Heat Transfer 6.1 Absorbing and Losing Heat Science 14 and 10-4 with Mrs. M.
![Page 1: Chapter 6 Controlling Heat Transfer 6.1 Absorbing and Losing Heat Science 14 and 10-4 with Mrs. M.](https://reader035.fdocuments.us/reader035/viewer/2022062304/56649d305503460f94a093d5/html5/thumbnails/1.jpg)
Chapter 6 Controlling Heat Transfer6.1 Absorbing and Losing Heat
Science 14 and 10-4with Mrs. M
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Specific Heat CapacityCan’t take the heat? Get out of the kitchen!
Just kidding, water can take the heat
• Water can absorb a lot of heat without raising its temperature a lot
• It takes a lot more heat energy to increase the temperature of water
• Water has a HIGH specific heat which means a LOW temperature compared to other substances
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• Heat absorption: the rate at which materials absorb heat
• Specific heat capacity: measures a substance’s ability to absorb or lose heat– Water has a high specific heat so it can take on a
lot of heat energy without increasing it’s temperature too much
Water Can Take the Heat
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Oceans moderate climate
• Oceans store thermal energy (heat)• Water can absorb heat on a hot day• Water can release heat on a cool day• Water’s specific heat capacity is larger than
that of oil, sand, or metal
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Fire walkers• Socks make their feet sweat before performing
the walk. How might this help to protect their feet from burning? https://www.youtube.com/watch?v=-iBFwpKV6ak
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Lab Report• Heat absorption and specific heat capacity
• There are equal amounts of water, vegetable oil, and vinegar in beakers on a hot plate. If all are given the same amount of heat, which will heat up fastest? Which will stay hot the longest?
• Analysis: Considering water’s specific heat capacity is 4.19 J/g°C and oil’s is 1.97 J/g°C, why do you think that you saw the difference in heating?
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Check Your Understanding Page 110
#3. Why does water at a beach feel cooler than sand during the day and warmer at night?
#4. Use your knowledge of specific heat capacity to explain why water is a better coolant than vegetable oil.
Relate your knowledge of specific heat capacity to coolant in a car radiator.
#5. You plan to make French fries. It’s best to use very hot oil
with a higher or lower specific heat capacity better? Why?
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Air vs. Water Heat Capacityhttps://www.youtube.com/watch?v=hyPLusD-tyM
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6.2 Keeping Heat at Home
• During winter, Canadian houses lose heat because hot air escapes to the cold outside
• Insulation can help this problem
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Conductors vs Insulators
• Metal• Ceramic• Electrical wire
• Glass• Wood• Plastic• Fabrics• Reflective foil
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Conductors vs Insulators
• Metal• Ceramic• Electrical wire
• Glass• Wood• Plastic• Fabrics• Reflective foil
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Why wrap food in aluminum/tin foil?
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Why do welders need equipment?
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6.2 Insulation
• Insulation slows heat transfer• R-value is a measure of how well an insulating
material slows heat transfer• High R-value means better insulation
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R-value
• The total R-value is the sum of the R-values of each material used
• Example: What is the total R-value if you have 25mm of expanded polystyrene and rigid urethane?– expanded polystyrene 3.96– rigid urethane 7.50– Total = 3.96 + 7.50 = R-11.46
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Check Your Understanding
• Page 119 #1aUse Table 6.2 on page 111 to help you calculate
the R-values of the following insulation materials:
a) 25 mm of air space + 25 mm of expanded polystyrene
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Cavity Walls• Walls often have a cavity of air in between the
layers• This air gap can be filled with insulation to
eliminate convection currents within walls
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What has a higher R-value?
• Double wall
• Double wall with insulation
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Check Your Understanding
• Page 119 #1
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Guest Speaker: Firefighter
Facts about fire:• Can be caused by overheating electrical wires,
kitchen fires, gas leaks
• Houses vaporize (flame over) at 1000°C so firefighters need to get out
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Firefighter Safety
• Firefighters are most likely to burn their ears, chin, and neck
• Protective gear is made of three layers– Kevlar: prevent injection (glass, needles)– Fire resistant: prevent heat transfer– Micro-fiber: waterproof prevents absorption
• Visor melts at 700°C to signal it is time to get out
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Firefighter Equipment
• Boots, pants, coat, helmet, gloves, mask
Cool Facts• Firefighter equipment is both expensive and
heavy
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Pop Can House
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Controlling Heat Transfer
• How do pizza deliveries keep your pizza warm?
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Windows and Doors Leak Heat
• How do we keep the heat in?
• Older houses have storm windows or storm doors. Two doors help keep heat in.
• Today we use an extra glazing on glass windows
• Weather stripping
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Why do builders put more insulation in attics than in walls?
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Asbestos
• Asbestos fibres are strong, durable and non-combustible
• Used widely in the ‘50s - ‘70s• People in construction, maintenance, and
renovation must be careful
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Asbestos• Good for reinforcing, insulating, fire-proofing• No risk if fibres are enclosed or tightly bound
in a product, (asbestos siding or floor tiles) • Asbestos poses health risks only when fibres
are present in the air that people breathe
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Asbestos
• https://www.youtube.com/watch?v=GjMsV4VsJew
• Until 3:45
• https://www.youtube.com/watch?v=BIHpsyuyV4I Thermal sensors
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How do police use infrared heat to find grow ops?
• Officers are trained to look for infrared hot spots on walls and windows, unusually warm foundations, and exhaust emissions
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Vacuum Bottle: Thermos
• Insulated to keep your food or beverage warm• Insulation slows heat transfer• How does it work?
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• Double glass jar (similar to double pane window)• Partial vacuum from removing
some air between glass jars• Reflective coating• Rubber/plastic outer case• Insulated cap
How does a vacuum bottle reduce convection, conduction, radiation?
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6.3 Keeping Cool
• People in deserts wear more clothes to minimize heat transfer
• You protect your hands from the oven’s heat using oven mitts
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6.3 Keeping Warm
• Multiple layers keep you warm in the winter
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Polar bears have hollow guard hairs
Air is an insulator
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Chapter 6 Review
• Key Term Definitions or Reviewing Key Terms• #2, 4, 7, 10, 12, 13