# HW 2 heat Ch. 9.2. Page 311 Ch. 9.2 Section Review 1.Blow on hands to warm them: If molecules in exhaled air have greater average KE than the surrounding.

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HW 2 heat Ch. 9.2

Page 311 Ch. 9.2 Section Review 1.Blow on hands to warm them: If molecules in exhaled air have greater average KE than the surrounding air, then heat will be transferred to your hands, causing an increase in temperature (This works as long as you open your mouth wide when you blow—reduces adiabatic effect)

Pg 311 1. Blow on a bowl of hot soup to cool: The molecules in the soup have a greater average KE than your exhaled air, so heat is transferred from the soup to the air (the cooling effect is increased if you purse your lips when blowing—increases adiabatic effect-air expands when leaving your mouth and cools)

Pg 311 2. Yes. The internal energy of the water increases because kinetic energy is added to the water by shaking. This kinetic energy (mechanical energy) is converted into the internal energy of the water molecules (non-mechanical energy)

Pg 311 3. If all GPE initial is transferred to internal energy, and KE final is zero, then PE + KE + U = 0 PE final – PE initial is 0 j – (505 kg x 9.81 m/s 2 x 50.0 m) KE initial – KE final = 0 J – 0J -248,000 J + U = 0 So U = 248,000 J

Pg 311 4.You would need to know the initial temperature of each bottle of water to compare the amount of heat transfer that will occur.

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