1. Controlling Heat Transfer Chapter Six REVIEW

2. Absorbing and Losing Heat Heat Absorption- refers to the rate at which materials absorb heat. Every material absorbs heat at a particular rate. Heat Absorption- refers to the rate at which materials absorb heat. Every material absorbs heat at a particular rate. Which will absorb more heat: a black sweater or a white sweater? Why? Which will absorb more heat: a black sweater or a white sweater? Why?

3. Specific Heat Capacity (SHC) Definition: a measure of the ability to absorb or lose heat. (J/g ̊ C) Definition: a measure of the ability to absorb or lose heat. (J/g ̊ C) SHC of water: 4.19 J/g ̊ C SHC of water: 4.19 J/g ̊ C –So, one gram of water absorbs 4.19 Joules to raise the temp. by 1 degree –One gram of water loses 4.19 Joules to lower the temp. by 1 degree

4. SHC of sand: 0.66 J/g ̊ C. Compare this to water’s SHC. Which will heat up faster? SHC of sand: 0.66 J/g ̊ C. Compare this to water’s SHC. Which will heat up faster? –Sand. Since it has a lower heat capacity it will warm up quicker. Think about being on a beach. The water is much cooler than that of the sand, because it takes longer to heat up water. Look at the table on page 109….tell me the heat capacity of: Look at the table on page 109….tell me the heat capacity of: –Air 0.995 J/g ̊ C 0.995 J/g ̊ C

5. Oceans You remember from chapter five that oceans heat up slower than the land…with the knowledge of specific heat capacity tell me why? You remember from chapter five that oceans heat up slower than the land…with the knowledge of specific heat capacity tell me why? –Water has a higher SHC than the land therefore the land is going to heat up faster while the water will heat up slower…storing lots of thermal energy which will be released at night with the warm night sea breeze.

6. Keeping Heat at Home Insulation- any type of material that will slow the heat transfer. Insulation- any type of material that will slow the heat transfer. –Home insulation: Winter: keeps the heat in and the cold out Winter: keeps the heat in and the cold out Summer: keeps the cold in and the heat out. Summer: keeps the cold in and the heat out.

7. R-Value Definition: measure of how well an insulating material slows the heat transfer. Definition: measure of how well an insulating material slows the heat transfer. High R-values = good insulators High R-values = good insulators Low R-values = poor insulators Low R-values = poor insulators Just like math, you can put insulators together and add their R-values…this would make a Total R-value. Just like math, you can put insulators together and add their R-values…this would make a Total R-value.

8. Example You make a home with 25 mm of soild wood, 25 mm of fibreglass, and 25 mm of clay brick. What is the R-value of your insulation? (Look at the table on page 111 to find the separate R- values). You make a home with 25 mm of soild wood, 25 mm of fibreglass, and 25 mm of clay brick. What is the R-value of your insulation? (Look at the table on page 111 to find the separate R- values). –Wood  R-value: 1.25 –Fibreglass  R-value: 4.25 –Clay Brick  R-value: 0.11 TOTAL R-value = 5.61 TOTAL R-value = 5.61

9. Wall Cavity Definition: This is the space between the inside wall and the outside wall of a house. Usually this space is filled with insulation which has pockets of still air (air that does not move). Definition: This is the space between the inside wall and the outside wall of a house. Usually this space is filled with insulation which has pockets of still air (air that does not move).

10. Windows and Doors Old: “storm windows” and “storm doors”…they are double windows/doors to keep heat in…as heat likes to sneak out between the panes of the window Old: “storm windows” and “storm doors”…they are double windows/doors to keep heat in…as heat likes to sneak out between the panes of the window New: “double glazing”…this is a double pane of glass with a space in between filled with argon gas. This slows heat transfer. New: “double glazing”…this is a double pane of glass with a space in between filled with argon gas. This slows heat transfer.

11. Controlling Heat Transfer Pizza delivery (box and insulated envelope) Pizza delivery (box and insulated envelope) Vacuum bottle: container that slows conduction, convection, and radiation. Vacuum bottle: container that slows conduction, convection, and radiation. –Double glass jar –Some air is removed from between jars –Have a silver reflective coating –Rubber or plastic keeps glass away from outer case –Cap insulated.

12. What is insulated? Stoves Stoves Refrigerators Refrigerators Freezers Freezers Dishwashers Dishwashers Pots  the plastic or wooden handle allows you to pick them up. Pots  the plastic or wooden handle allows you to pick them up. Toasters  encased in plastic Toasters  encased in plastic

13. USE OVEN MITTS Why do we use oven mitts? Why do we use oven mitts? Duh, right? Duh, right? We do not want to burn ourselves when we take hot things out of the oven. We do not want to burn ourselves when we take hot things out of the oven.

14. Keeping Yourself Warm How do we keep ourselves warm during the winters? How do we keep ourselves warm during the winters? –We layer up. Just like in insulation. –Down- when it’s fluffed it holds air in place –Layer up when you are going to be outside….when you start sweat remove a layer as it will make you colder. This will keep the heat transfer constant, thus keeping your body at equilibrium.

15. Inuit Cold days: inner suit is fur next to the body which soaks up the body moisture and transfers it to through the leather. Outer suit is worn with the fur to the outside. The fur around the face warms the air so that the air breathed in is warmed. Condensation from the breathing will not cause ice because of the fur. Cold days: inner suit is fur next to the body which soaks up the body moisture and transfers it to through the leather. Outer suit is worn with the fur to the outside. The fur around the face warms the air so that the air breathed in is warmed. Condensation from the breathing will not cause ice because of the fur.

16. Hot Areas They wear a lot of clothes to minimize heat transfer. They wear a lot of clothes to minimize heat transfer. Covering…protects skin from the sun’s rays Covering…protects skin from the sun’s rays Light coloured clothing…absorbs less heat Light coloured clothing…absorbs less heat

17. Firefighters Suits contain flame retardant materials which only chars. Suits contain flame retardant materials which only chars. Inner material absorbs body moisture, keeping firefighter cool. Inner material absorbs body moisture, keeping firefighter cool. Firefighters can still suffer heat stroke. Firefighters can still suffer heat stroke. All firefighting gear must pass safety inspection and testing! All firefighting gear must pass safety inspection and testing!

18. Divers Tight suits prevent cold water from cooling the skin by conduction (what’s conduction?) Tight suits prevent cold water from cooling the skin by conduction (what’s conduction?) Suits are made of neoprene with bubbles of nitrogen trapped in the fabric (keeps body heat inside) Suits are made of neoprene with bubbles of nitrogen trapped in the fabric (keeps body heat inside) They have hoods for the same reason. They have hoods for the same reason.