Lecture25

Physics 101: Lecture 25 Heat ,[object Object],Final

Internal Energy ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Heat ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Specific Heat ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Act ,[object Object],[object Object],1 liter = 1,000 grams of H 2 0 1000 g x 1 calorie/(gram degree) x (36 degree) = 36,000 calories 36,000 calories = 36 Calories!

Preflight 1 & 2 ,[object Object],[object Object],[object Object],[object Object],Aluminum block has higher specific heat constant, so it will release more heat to the water. Correct (52%) Substance c (heat capacity) J/(kg-C) aluminum 900 copper 387

Specific Heat ACT Suppose you have equal masses of aluminum and copper at the same initial temperature. You add 1000 J of heat to each of them. Which one ends up at the higher final temperature A) aluminum B) copper C) the same  T = Q / cm Correct Substance c in J/(kg-C) aluminum 900 copper 387 iron 452 lead 128 human body 3500 water 4186 ice 2000

Specific Heat for Ideal Gas ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Latent Heat L ,[object Object],[object Object],T Q added to water water temp rises water changes to steam (boils) steam temp rises 100 o C Latent Heat Substance L f (J/kg) L v (J/kg) water 33.5 x 10 4 22.6 x 10 5

Ice Act ,[object Object],[object Object],Latent Heat L [J/kg] is heat which must be added (or removed) for material to change phase (liquid-gas). T Q added to water ice temp rises ice changes to water (melts) water temp rises 0 o C Latent Heat Substance L f (J/kg) L v (J/kg) water 33.5 x 10 4 22.6 x 10 5

Cooling Act ,[object Object],[object Object],Q evaporative = L m = 2.2x10 6 J Q c = C M  t = 4.2 x 35 x M M = 2.2x10 6 / 147 = 15,000 g or 15 liters!

Preflight 3 ,[object Object],[object Object],the latent heat from of the evaporation of water causes the cooling effect. I really have no idea....I'm dreaming of turkey... Goosebumps are a physiological phenomenon inherited from our animal ancestors, which was useful to them but are not of much help to us. Goosebumps are tiny elevations of the skin that resemble the skin of poultry after the feathers have been plucked. (Therefore we could as well call them "turkeybumps" or "duckbumps.") These bumps are caused by a contraction of miniature muscles that are attached to each hair. Each contracting muscle creates a shallow depression on the skin surface, which causes the surrounding area to protrude.

Cooling ACT ,[object Object],[object Object],PV = nRT

Cooling ACT continued… ,[object Object],[object Object]

Cooling Act Continued… ,[object Object],[object Object]

Example ,[object Object],[object Object],Key ideas 1) Q leaving water goes into heating ice. 2) Final temps are same

Summary ,[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object],[object Object]

Lecture25

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Lecture25

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