Answers to the Feb. 27 In-class Optional Assignment

Question #1

There are at least two phase changes occurring in the picture above.  What are they?
The dry ice is sublimating (changing from a solid directly into invisible CO2 gas).  Water vapor is condensing to form the cloud (colored green).  The condensing water vapor may actually be turning into ice crystals, that would be deposition.  Eventually the cloud evaporates.

Is energy being transported from the air INTO the dry ice or AWAY FROM the dry ice & into the air?
(hint: the visible cloud is not carbon dioxide gas)
Energy is flowing from the warmer air in the room INTO the dry ice.  Energy is also flowing INTO the dry ice from the condensing water vapor.

Question #2
The person is trying to cool the hot steaming bowl of soup by blowing on it.

What two energy transport processes are at work here?
(hint: you've seen that head before that should suggest at least one answer)
The blowing is forced convection.  The hot soup is also evaporating.  Evaporation will take energy from the soup and cause it to cool (just as you cool when you step out of the shower and water on your body begins to evaporate)

Question #3
A person is standing outside on a cold windy day in A,
has fallen into cold water in B, and is perspiring heavily in C.
Match each energy transport process below with the most
appropriate situation in the drawing.

Conduction___B____   Convection ___A___   Latent heat ___C____

Question #4
Would the formation of a cloud  WARM  or  COOL  the surrounding air?
Water vapor condenses to form a cloud.  The condensation will release energy into and WARM the surroundings.
Does the formation of frost  WARM  or  COOL  the air?
Same kind of situation except that water vapor is changing directly to ice.  This releases energy into and WARMS the surrounding air.

Question #5
Who or what do you think showed up at my back door Thursday evening while I was trying to watch American Idol, record Survivor, and talk on the phone? 
A raccoon!  It showed up again on Sunday night.  Here are a couple of pictures from the Sunday night visit.

Question #6
Would the electric field at a point midway between the + and a - charge
point UP  DOWN  RIGHT  LEFT  or would the electric field be ZERO?


Imagine sticking a + charge in between the two charges above.  The charge will be repelled by the + on the left and attracted by the - on the right.  The charge will move right. The electric field arrow will point to the RIGHT.