Ice Melting Lab

I didn't think a proper handout was necessary for this short demonstration, but I'll write a little something to help with your writeup over the weekend. Yours shouldn't be longer than a page or so.

In the Ice Melting demo we are concerned with two things. 1. the way in which heat is transferred to other materials. 2. which materials conduct heat efficiently. The answer to the first question is the zeroth law of thermodynamics. That's not very helpful, but I'll put down a definition according to my text book, "Every body" (not everybody, though that is also true) "has a property called temperature. When two bodies are in thermal equilibrium, their temperatures are equal. And vice versa." Said otherwise, so long as two bodies in a closed system have different temperatures, there will be a transfer of heat i. e. they will not be in thermal equilibrium. A third way of saying it: When  enough heat is transferred so that two bodies, which are in contact, are the same temperature they are considered to be in thermal equilibrium. Until thermal equilibrium is reached they will transfer heat betwixt themselves.

Whew, got it? If not there is a comment section for you to ask me something, or wait till class on Monday.

The second part is simpler I think. In the second part we are simply measuring which kinds of materials of more capable of transferring heat quickly from one place to another. A material which 'conducts' heat well, like our metal plate, is able equalize temperatures quickly, whereas a poor conductor, like the Styrofoam, absorbs the cold of the ice only on one small part of it. 

Put the two parts together and you have something like this: 1. Two bodies in contact with each other will transfer heat until their temperatures are the same. 2. Some materials transfer heat quicker than others. 3. Therefore when bodies of two different temperatures are in contact with each other, bodies that are able to quickly transfer heat i. e. conductors, will manage to gain thermal equilibrium faster than poor conductors.

I hope this helps. See you all soon.

Lab # 1 Our Very First Handout

Lab #1: The Sensation of Heat

Introduction:

We are trying to discover something about the way we perceive heat.  Upon what does our sensation of heat rest?  To find a way into this question we will use the scientific method.

Materials:

The air                                                                                      – symbol: A

Wood (cabinet doors)                                                                          – symbol: WD

The classroom wall                                                                              – symbol: DW

Glass (specify if you use a window, the fish tank or the cabinets–           - symbol: G

The metal leg of your chair                                                        – symbol: L

The top of the table                                                                               -symbol T

Our Hands                                                                                           -symbol H

Temperature strips

Procedure:

Using your entire palm as your ‘warmth sensing device’, feel each of the objects listed above for 1-5 seconds (enough to get a good report from your warmth sense but not long enough to let the heat from your hand warm the object too much).

Really pay attention to the sensation of warmth or coldness for each object, then put them in order of “Warmest” to “Coldest”, with #1 as the warmest and #7 as the coldest:

#1:_____________________ (warmest)

#2:_____________________                        

#3:_____________________                         

#4:_____________________                         

#5:_____________________                          

#6:_____________________                         

#7:_____________________ (coldest)          

When you are done rating the materials, go to the board and record your results in a column using the symbols provided in the materials section.

Dip you hands in water that is at room temperature. Let them sit for a little while. Try touching the objects again and noticing any changes in how they feel, heat wise. Try touching 1 dry hand with the wet one. See how the sensation differs.

Now dip you hands in the cold water for 30 seconds or so. Those squeamish about cold don’t have to do this. After your hands have adjusted to the water try touching the same objects and rating them again. Also notice if some objects feel warmer/colder than they used to. If your hand warms up too much, return to the cold water to test again. 

Try doing the same with warm water.

Once all observations have been recorded, we will get an assessment of the temperature of each object with the help of some thermometer strips.  Record the temperatures reported by the thermometers in the last column of the chart below.

Now you will need to copy from the board the entire class’ results, to compare with your own.  This helps us get a more comprehensive picture of the experiment because we don’t have to rely on any single person’s results, which may be wrong.  Use the table below to record the entire class’ results:

Put YOUR results in column 1. Record the actual thermometer temperature reading in the last column.

Warmest	1	2	3	4	5	6	7	8	9	10	11	12	13	14	15	16	17	Temp
Neutral
Neutral
Coldest

                                                                                                                                                                                     

Things to include in your analysis/conclusions section of your writeup:

Why might some of the objects feel warmer than others?

Did you expect certain objects to be warmer or cooler than others?  Why?

Is there a discrepancy between what you experienced and what the thermometers report or not?  Explain.

Can you make any reasonable conclusions about your sense of warmth? (What are the factors that play into this sense?  In other words, what are all the things that, if they changed, would change our sensation of warmth?)