1. Heat and Its Uses Work can be changed into PE or KE, and vice versa So they are the same thing, in a different form Heat is also a form of energy -can change heat into PE (cooking) -can change heat into KE (drag race)

2. Heat is Energy (cont.) Can change work into heat and heat into work So Heat is a form of Energy *

3. Originally, scientists thought heat was an invisible fluid they called a “caloric” This information is wrong Don’t write it down! So heat “flowed” from a hot object to a cold object (we still use these terms today) Evidence: As objects heat up, they get larger; when they cool down, they get smaller We can now explain the change in volume in a different way, assuming heat is energy

4. Heat energy is stored in objects in vibrational kinetic energy of particles Heat is Energy (cont.) As heat is added to an object, its particles vibrate faster Particles need more “elbow room” and so they spread out; this is called thermal expansion (You can start writing again)

5. Thermal Expansion: All matter expands when heated; due to increased KE of particles Solids example: gaps between rails on a railroad track (expansion joints)

6. Liquids example: thermometers Gases example: balloon in boiling water

7. Heat vs. Temperature Take a cup of coffee and a swimming pool outside on a day that it is below freezing. Which will freeze first? Coffee is at a higher temperature, but the swimming pool contains more heat, because there’s much more mass High temp. More heat content Coffee

8. Temperature: a measure of the average KE of the particles of a substance Heat: a measure of the total thermal energy of the particles of a substance Coffee’s particles are moving faster, on average, than the water molecules in the pool But because there are so many more water molecules in the pool, it takes longer for them to give up their thermal energy to the air

9. Specific Heat Capacity : the ability of a substance to absorb or release heat Example of a substance that absorbs heat well: metals Example of a substance that does not absorb heat well:wood The metal parts of your desk “feel” colder than the plastic parts, because the metal absorbs heat from your hand much faster than the plastic

10. Substances that absorb heat quickly also release heat quickly; so metals cool down faster than wood example: pizza on aluminum foil Other good heat absorbers: -sand, earth, metals Other poor heat absorbers: -water, glass, plastic, air, wood

11. 3 Methods of Heat Transfer (1) Conduction:transfer of heat by collisions Heat one end of a metal rod; end particles vibrate faster (more KE); collide with neighbors, causing them to vibrate faster (and heat up); continues all the way down rod xxxxxxxx

12. (2) Convection:transfer of heat by moving fluids ex. Radiators (home heating) Equator North Pole Deserts also causes weather

13. transfer of heat by electromagnetic radiation (infrared); can travel through a vacuum (3) radiation:

14. Wind Chill is the perceived decrease in air temperature felt by the body on exposed skin due to the flow of air. Two kids in separate places: JohnBill Air Temp. = -10 o F Winds: Calm Air Temp. = 20 o F Winds: 20 mph Which guy feels colder?

15. JohnBill Air Temp. = 10 o F Winds: Calm Air Temp. = 20 o F Winds: 20 mph

16. Put 2 glasses of water outside on a 35 o F day. Glass A is in a calm area while Glass B is in a 10 mph wind. 1. Glass A’s water will freeze but B’s will not 2. Glass B’s water will freeze but A’s will not. 3. Both will freeze. 4. Neither will freeze. Which of the following will occur?

17. Put 2 glasses of water outside on a 35 o F day. Glass A is in a calm area while Glass B is in a 10 mph wind. 1. Glass A’s water will freeze but B’s will not 2. Glass B’s water will freeze but A’s will not. 3. Both will freeze. 4. Neither will freeze. Which of the following will occur? Glass B will cool down faster to 35 o F Wind chill does not effect inanimate objects.

18. Heating Systems To heat a building, you need:(1) Fuel (2) A Delivery System FuelDelivery System Natural gas Liquid Propane Oil Wood Coal Forced air Forced water Natural convection Other ways: Solar, Electrical

19. Insulation Used to prevent heat transfer Made of materials that have many layers, or many boundaries Every time heat crosses a boundary, some is reflected back

20. Examples of Insulation Techniques: Layered clothing Fiberglass insulation in homes Weather stripping around doors Double-paned windows - air insulates well

21. Good insulation prevents heat transfer by: Conduction: By using poor heat conductors such as glass, air, or a vacuum

22. Convection:By having air pockets that are too small for convection currents to form And by

23. Radiation:By using metal foil to reflect IR radiation And by

24. Animals insulate themselves: Birds ruffle their feathers

25. Ice Cube Box Project Task: To build a box that keeps an ice cube frozen for as long as possible Specifications: Must be no longer than 4” on any side, or diameter (if a cylinder) Must hold an ice cube of volume 1 in 3 Must be able to be opened and easily re-closed

26. I will provide: Masking tape Cutting tools Ice cube You provide:Cardboard or whatever material makes the container. Insulating material We will work on this one day in class At the end of the period you will place the ice cube in the box. I will check them periodically until they are melted

27. Complete a box with appropriate insulating materials (5 pt. penalty per specification violation) 60 Ice cube lasts 2 hours before melting70 3 hours75 4 hours80 5 hours85 6 hours90 7 hours95 8 hours100 Each subsequent hour+5 pts. Rubric: