Purpose
To investigate thermal energy conservation, i. e., test the hypothesis that energy is conserved.
Preliminary Questions
1. You place a new room temperature 2 liter soda bottle in your refrigerator. The next day you put three new 2 liter soda bottles in your refrigerator. Which set of soda bottles had more energy removed?
2. You are going to boil a pot full of water starting with cold water from the tap. You then boil another pot full but start with hot water from the tap. Which pot had more energy added to raise the temperature to the boiling point?
3. You have 1 gram of water and add enough energy to raise its temperature 1ûc. How much more energy must be added to raise the temperature another 1ûc (compared the to first energy added)?to raise it 5ûc? to lower it 10ûc?
4. If you took the energy changes found in question 3 and divided each energy by its associated temperature change, how would the values compare?
5. You have 1 gram of water and add enough energy to raise its temperature 1ûc. How much more energy must be added to raise the temperature 1ûc if there was 2 grams of water (compared the to first energy added)? if there was 5 g of water?
6. If you took the energy changes found in question 5 and divided each energy by its associated mass, how would the values compare?
7. In general, for the same material, explain why you would or would not expect the specific heat to be constant.
Apparatus
Double-walled calorimeter, water, metal samples, thermometer, steam generator, paper towels, string, and balance.
Suggested Procedure
Caution, you will be working with steam and hot metal this lab.
Assume you can identify and quantify all the objects which gain and loose thermal energy (temperature related energy, colloquially called heat). If energy is conserved, then added the total energy gained by objects must equal the total energy lost by the other objects. (Can you explain why?)
E gained object 1 + E gained object 2 + E gained object 3 + … = E lost object 1 + E lost Object 2 + E lost Object 3 + …
Further, assume the specific heat is constant for a given material, but it may be different for different materials. The specific heat equation can be rearranged to
Echange = m c (T final -T initial)
or
E gained = m c (T final -T initial) and E lost = m c |T final -T initial| = m c (T initial -T final) .
These relations can be substituted into the energy conservation equation above.
Use the above relations to measure the unknown
specific heat of different materials. (Note, the specific heat for
water is defined as 1 
= 4.186 
at room temperatures and pressures).
Hypothesize how your specific heat value for a given material should compare to the measured values others get for the same material.
Determine the mass of all the materials relevant to the energy exchange (the sample, inner cup of the calorimeter, the water in the calorimeter (use as little as possible, but enough to cover the sample completely). [As a first approximation, assume only the water and the metal sample exchange energy.]
Raise the temperature of the metal sample in a steam generator by immersing it in the boiling water for a few minutes.
Record the starting temperatures of the sample and the water in the calorimeter cup.
Quickly transfer the metal sample to the calorimeter.
Record the final temperature. (Should you be stirring the water while you are waiting for this reading? Explain.
Repeat the experiment a for the same or different metals as instructed or as you dicide appropriate.
Analysis
Apply your energy conservation assumptions and determine the specific heat of each sample. Compare results.
Questions:
1. What are unaccounted ways energy can escape from or be added to the system?
2. How would you correct the energy conservation equation to include the energy associated with it (or ignore the cup if you included it)? Does including (excluding) the effect of the cup energy tend to increase or decrease your measured specific heat?
3. You added energy to the sample by immersing it in boiling water. Another method would be to hold it in the steam above the boiling water. Which method is better and why?
4. To improve on the accuracy of this experiment, one can start with water that is slightly cooler than the room's temperature and end up with a final equilibrium temperature that is slight warmer than room temperature. Why might this improve the accuracy of your result?
5. List all the ways liquid water contains energy (Hint, imagine starting with no energy or the minimum energy possible and add energy to get to where you want)?
6. Is it possible to test energy conservation without knowing how much energy the objects involved contain?
7. Two people are burned on the arm. One is burned by 15 g of water at 100ûc (212ûF). The other is burned by 15 g of steam at 100ûc (212ûF). In both cases, the final temperature is 37.8ûc (100ûF) and all the energy is shared by the body and the fluid. Compare the burns of the two people, justifying your statements as much as possible.