Experiment 2

Heating it Up!

Which Fuel Source Has More Heat Energy?

A Comparison Of The Amount Of Energy Given Off In A Combustion Reaction

Objective:

There are two objectives for this experiment. The first is to compare possible fuel sources for the amount of energy they give off in the form of heat energy. The second is to tell which one(s) are cleaner burning fuels than the others.

Review of Scientific Principles:

We are always looking for alternative energy sources since fossil fuels are nonrenewable resources. There are two questions frequently asked when considering an alternative fuel. How much energy will be released per unit of that resource, and what effects might burning it have on the environment? When we use a resource, such as coal, oil, or natural gas to produce energy, we are breaking the chemical bonds within the substance and rearranging them into more stable bonds. This change results in the formation of different products, such as carbon dioxide and water in the case of combustion, and a release of energy. How can we measure the amount of energy?

If we tried to quantify it mechanically, we may never know just how much absolute energy is in the resource itself. Therefore, we use the "heating value" of fuels: how using so much of a certain resource (rearranging its bonds into a more stable state) converts to so much heat (motion of molecules). We all hear every day about counting calories. What is a calorie? A calorie (cal) is defined as the amount of heat needed to raise one gram of water 1o C. A food calorie actually consists of one kilocalorie, or 1,000 calories. Why do we worry about calories in relation to our weight? Energy conservation! If you feed your body more calories than it can use, it will store the energy in a stable state like body fat for you to use and lose later.

For this lab, we will measure the amount of the temperature change and use that to indicate heat energy. Temperature is defined as the average kinetic energy of all the molecules, and heat is the movement of molecules.

Materials and Supplies:

Procedure:

  1. Bend the paper clip so that it looks like this:
  2. Weave the paper clip in and out of the outer most layer of the clothesline so it looks like this:
  3. Measure 100 ml of cold water with a graduated cylinder and pour it into a soda can.
  4. Place the stir rod through the tab of the pop can.
  5. Set the stir rod on top of the ring, letting the can hang beneath --see figure below.
  6. Place the thermometer in the can so that
  7. it can be easily read;
  8. it is in the 100 ml of water in the can;
  9. it is supported by a clamp on the ring stand.
  10. Put 20 drops of your substance on the clothesline and place it below the can.
  11. Adjust the height of the ring so the can is 5 cm above the paper clip apparatus.
  12. Measure and record the initial temperature of the water in the data table.

    The apparatus should look like this:

  13. Have the teacher ignite the clothesline and observe the flame; record your observations.
  14. Let the clothesline burn until the flame disappears and place the smoking remains in a beaker of water.
  15. Record the final temperature of the water in the data table.

Video Clip

Data and Calculations:

SubstanceInitial Temperature oCFinal Temperature oCAppearance of fumes from burning
Methanol
   
   
   
Ethanol
   
   
   
Vegetable oil
   
   
   
Peanut oil
   
   
   
Motor oil
   
   
   
Kerosene
   
   
   

  1. Calculate the difference in the temperature for all the samples tested.

    Methanol
    Ethanol
    Vegetable oil
    Peanut oil
    Motor oil
    Kerosene

  2. Which 'fuels' burnt the cleanest?

  3. Which 'fuel' source had most heat energy?

  4. Were you able to measure the total amount of energy released? Why or why not -- explain your answer fully.

  5. Does the fact that the clothesline may burn affect this comparison of 'fuel' sources? Explain your answer fully.

  6. What 'fuel' do we put in our bodies? How is what happens in your body with that 'fuel' similar and dissimilar to how 'fuel' is used in your car?


Experiment 2: Teacher's Notes

Heating it Up!

Which Fuel Source Has More Heat Energy?

Prep Time: 10 minutes

Time: 45-50 minutes

Because of time constraints it works best to 'jigsaw' this lab or have each group do a separate part of this lab; then share their results. Divide the class into six groups (or any multiple of six groups). In order to facilitate this, you'll need to make six clearly labeled 10 ml disposable eye droppers.

Add 10 ml of methanol, ethanol, motor oil, vegetable oil, peanut oil, and kerosene in six different droppers. Label the droppers accordingly. Store upside down in a 50 mL beaker. As you assign each group the material they are to test, point out what table that material is on.

Each group needs to burn the sample they have prepared until the flame extinguishes by itself. (Smoldering samples should be removed and placed in a beaker of water.

Sample Data:

SubstanceInitial Temperature o CFinal Temperature o CAppearance of fumes from burning
Methanol2934clean burning
Ethanol2842clean burning
Vegetable2856sooty oil
Peanut oil2850sooty
Motor oil2755sooty
Kerosene2349sooty

Calculations:

  1. Calculate the difference in temperature for all the samples tested.

    Methanol6 oC
    Ethanol13 oC
    Vegetable oil28 oC
    Peanut oil22 oC
    Motor oil28 oC
    Kerosene26 oC
  2. Which 'fuels' burned more cleanly? Ethanol and Methanol burned the cleanest.
  3. Which 'fuel' source had most heat energy? Vegetable oil and motor oil released the most heat energy.
  4. Were you able to measure the total amount of energy released? Why or why not ? Explain your answer fully. No, because some heat energy escaped into the surroundings. Also, energy in the form of light was given off.
  5. Does the fact that the clothesline may burn affect this comparison of 'fuel' sources? Explain your answer fully. Yes. Since different fuels may release more energy, different amounts of clothesline may burn for each, causing different amounts of heat to be released.
  6. What 'fuel' do we put in our bodies? How is what happens in your body with that 'fuel' similar and dissimilar to how 'fuel' is used in your car? Food. Food is used for energy to fuel your body processes, such as protein production, growth, and physical activity. Fuel in your car is just used for energy.

Next Topic: Experiment 3

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