Thermochemistry.

Heat vs. Temperature Lab and Specific Heat Lab and Heat of Fusion Lab

  1. Heat vs. Temperature Lab.
    This lab is designed for you to find out the difference between heat and temperature. No introduction/background is needed, the hypothesis information was given in class. The procedure is given in a handout in class; you do not need to copy this. You will be using the computers in the lab to record temperature data in various situations. Make your graphs at least half a page and clearly label all of your data. You will then analyze the data by answering questions.

    Questions:

    1. Part 1
      1. Using your observations and the graphs, explain what you observed. Label the regions of the graph that you describe in your discussion. Be sure that you clearly identify the similarities and differences between the events that occurred in beaker A vs. beaker B as part of your explanation. Discuss what happened in beakers A and B in terms of heat and temperature.
      2. How would your observations change if you started with 50 mL of water in A and 75 mL of water in B?
      3. What happened to the temperature of the water in each beaker as the water boiled? Explain why this happened.
      4. How would your results have changed if you would have used a different liquid, like cooking oil or alcohol, instead of water? Explain your reasoning.
    2. Part 2
      1. How did the use of different volumes affect the final temperature?
      2. Find a mathematical relationship that will allow you to calculate the final temperature of any combination of warm and cold water. Use your experimental data to test your relationship.
    3. Part 3
      1. Explain what happened in each experiment with respect to heat and temperature as you added more objects. Was there an obvious progression as you added more objects?
      2. What can you say about the ability of solid objects to hold heat as compared to water's ability to hold heat? How can you support your answer?
  2. Specific Heat of a Metal.
    In this lab you will be given two different metal samples. The purpose will be for you to find the specific heat of those two samples using your own procedure; the values will then be compared to the accepted values given later. You need to write a complete introduction/background. In that, include information about specific heat, the equation needed to find specific heat, and other relevant information. Be sure to discuss the experiment. In your hypothesis state the accepted values.
    After the background, write your procedure. Be complete, stating exactly what steps need to be done in order for someone else to find the specific heat of any sample.
    Show all data, clearly labled. In the data analysis make sure you include equations used and show all calculations, clearly labled. Compare your results to the accepted values for your metal samples. Find the % error for your values using the equation given below. Write the evaluation and conclusion as usual. In your evaluation, be sure to include the effects of your lab errors on your results.

    %error = [(Accepted value - Experimental value) / Accepted value] * 100

    The accepted values for the samples are:

    Metal 

    Specific Heat (J/(g °C))

     Aluminum

    .901

     Iron

    .450

    Lead

     .128

    Copper

    .387
  3. Heat of Fusion of Ice.
    In this lab the heat of fusion for ice will be found. You need to write an introduction/background section. Include in this section the definition of heat of fusion, discuss calorimetry and how it works, and other relevant information. In your hypothesis, state the accepted values for ice, in both kJ/mole and J/g.
    Procedure:
    1. Mass a dry styrofoam cup. Record.
    2. Measure 50.0 mL of ~50 °C water into a styrofoam cup. Mass and record.
    3. Using the temperature probe on the computer, measure and record the temperature of the water.
    4. Add 2-3 ice cubes to the water. Stir gently with the temperature probe. Before the ice is completely melted, add another ice cube.
    5. Continue adding ice cubes one at a time until the temperature plateaus. Record the final temperature.
    6. Carefully pull out the remaining ice cubes, allow the water to drip back into the cup. Mass and record.

    Data: Make up your own table with the necessary information.
    Data Analysis: Make sure all equations used are shown in your calculations.

    1. Find the mass of water originally in the cup.
    2. Calculate the amount of heat the water gave to the ice cubes. Use the mass of water and the change in temperature.
    3. Calculate the mass of ice which melted.
    4. The amount of heat released by the water (and calculated in step #2) is equal to the amount of heat absorbed by the ice. Knowing this and the mass of the ice, calculate the heat of fusion of ice in units of J/g.
    5. Convert your answer in step #4 to kJ/mole of ice.
    6. Find % error.
    7. Why was 50 °C water used as opposed to room temperature water? (Hint: Think of heat exchanges.)

    Evaluation and Conclusion: As usual, per the lab format handout.

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