[autopsy]

Hey all. I really need some help with a lab sheet I need to turn in.  Our instructor handed out a few unknown metals to each of our lab groups.  The goal was for us to identify the metal and I am having some real trouble. The mass of the sample was 17.75g. The mass of the calorimeter was 9.10. The mass of the calorimeter + water = 55.55g, so the mass of the water = 46.45 g. The initial water temp was 21.5C, temperature of heated metal sample was 88C, final temperature of water and metal 25.8 C, so I calculated the change in water temp to be 4.3, change in temp of the metal sample 62.2. Specofoc heat of water is 4.184 J/g C. First they want... the heat gained by the water... so i set my equation as follows. (46.45)(4.184)(4.3)=8.36x10^2 ... the lab manual said that heat gained by water is equal to the heat lost by metal.  So the heat lost by the metal would also be 8.36x10^2.  Finally they want the specific heat  of the metal. I set my equation up as follows....   8.36x10^2 / (17.75)(62.2) = 10.95 J/g C .  This is not one of the specific heats he gave us for the unknown metals, it is extremely high, we are to get numbers such as .900, .385, .131, .451, .128, .237, .222  Im not sure what I did wrong in calculations to get such a large number.  I have gotten A's on all my labs so far and am usually pretty sharp with getting correct data, and our instuctor helped us do the majority of it. Any suggestions? I would really appreciate it. Steph

[enahs]

8.36x10^2 / (17.75)(62.2) = 10.95

You typed it in your calculator wrong or something, as that is not what you get when you do that math. Though when you do it correct, it does not come out to one of the possible answers you gave.

Also, the metal was 88C? Are you sure? That seems like a pretty random number. The typical way to do this experiment is to submerge the metal sample in boiling water for a few minutes, so the metal becomes 100C.

[autopsy]

Yeah, For my data I have 88C. We did boil the water, but we had an unknown metal cylinder inside a test tube which was submerged in that boiling water, and the thermometer was in the test tube with the metal not the water itself, so 88 was highest we could get it to read when the water was boiling hard. Is that not correct?

[Borek]

Metal should have the same temperature biling water had. Unless you are living somewhere high (Nepal?) 88 deg C looks bit too low.

[autopsy]

Okay well my data must be incorrect, its probably too late to fix that. But there are some questions in the post lab I also have difficulty answering correctly. Firstly, why did I heat the metal in a dry test tube rather than in the boiling water? ..Is it just so I could a more accurate temperature of the metal itself rather than the water.   Also it asks, What effect does the initial temperature of water have on the change in temperature of the water after the hot metal is added? . I have just one more question. further on in the lab it gives youa chart with  the spec heat, and atomic mass of about a dozen metals it asks you to make a graph.  I chose to make a line graph and my finding is that the higher the atomic mass the lower the specific heat, and vice versa. But the part after I made the grpah it asks.... From the chart, what is the independent variable? Which is the dependent variable?

[Sev]

From the chart, what is the independent variable? Which is the dependent variable?

The independant variable will be atomic mass.  This should have been determined before plotting the graph (it is convention to have independant variable on horizontal axis).