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lab_effective_use_of_a_bunsen_burner by cuiliqing


									Chemistry              Lab: Effective Use of a Bunsen Burner                            1

                                                  Name _____________________

Lab: Effective Use of a Bunsen Burner                          Date________ Per______
To prepare this lab: Read the problem, skills, materials.
Highlight: Safety and Procedure. Answer: Pre-Lab Questions.

             Problem: How far from a flame should a beaker              of water be
            positioned for heating with a Bunsen burner to be           most
                    Lab Skills: Put safety first and 1) Heat a beaker of water using
            a Bunsen burner. 2) Measure distances using a ruler. 3) Measure
temperature using a thermometer.

Materials: 100 ml graduated cylinder, 250 ml beaker, Bunsen burner, striker,
thermometer, ring stand, ring clamp, wire gauze, ruler, stopwatch, beaker tongs, tap

Safety Precautions: Always wear safety goggles and a lab apron; Pull hair back
from face; Never eat or taste any substance used in the lab; Assume all glassware is
hot and handle with beaker tongs; Boiling water can burn skin. Dress for safety,
including closed toed shoes.

Pre-Lab Questions and Hypothesis:
   1. What are the constants in this experiment?

   2. What are the variables in this experiment?

   3. Which measurement in this experiment is the dependent variable?

   4. How will you know when the water is boiling? (you need both a temperature and
      visual clues).

   5. Read over the entire laboratory activity. Use complete sentences to complete
      the following: Make a hypothesis about the most effective position above
      the flame; include both a prediction and a reason.
Chemistry             Lab: Effective Use of a Bunsen Burner                             2

  Part I: Lighting and Adjusting the Bunsen Burner—
      1. Connect the Bunsen burner to the gas outlet with the rubber tubing.
      2. Light the burner: INITIAL ADJUSTMENT: use the gas adjustment valve
         (wheel) on the bottom of the burner to make sure it is part way open, by
         turning the wheel clockwise. Use the air vent adjustment to make sure there
         is some air entering the metal tube of the burner by turning the tube
         counterclockwise until you can see a hole at the base of the metal tube.
         LIGHTING: use the striker to make a spark. Push in on the striker as you pull
         the flint across the file. To light the burner, turn on the gas outlet. When the
         gas outlet handle is parallel to the hose fitting it is ON. When the handle is
         perpendicular to the hose fitting it is OFF. Keep your head away from the top
         of the burner. Hold the striker over the top of the metal tube of the burner and
         cause a spark. The gas should ignite.

      3. ADJUSTING THE FLAME: Use the gas control valve (wheel on bottom of
         burner) to make the flame shorter or taller. Use the air vent adjustment to
         make the flame hotter or cooler. A yellow flame is cooler than a blue one.
         The hottest flame is blue with an outer and an inner blue cone and a rushing
         sound from lots of air.
         Adjust the flame to a tall yellow flame, then change it to a short hot blue
         flame. The flame for the lab should be about 4-6 inches tall.

      Part II: Boiling water and testing different heights.
   1. Set up a ringstand and attach the ring clamp to the stand. Place the wire gauze
      on the ring to provide a platform on which to place the beaker of water.
   2. With a graduated cylinder, measure 100.0 ml of cold tap water into a 250 ml
      beaker. Measure the temperature of the water. Record the starting temp.
   3. With your Bunsen burner lit and adjusted to a hot, 4-6 inch flame, adjust the
      height of the ring clamp so that the ring is at the top of the outer blue cone of
      flame. Measure the distance from the top of the burner to the bottom of the ring
      clamp. Record the distance as test height #1 in centimeters.
   4. Make descriptive observations of the water, before, during heating and at boiling.
      Make descriptive observations of the flame before putting it under the beaker and
      in the middle of heating. Include a colored picture of the flame and ring stand set
      up, before and during the heating of the water.
   5. With the ringstand set up and beaker at room temp, place the beaker of 100.0 ml
      water on the wire gauze. Start the timer when the burner is placed under the
      beaker. Heat the water in the beaker until it boils. Use the thermometer to help
      determine when the water is boiling. Stop the timer when the water first boils.
      Record the time for boiling.
   6. Turn off the burner. Use the beaker tongs to remove the beaker of hot water from
      the wire gauze. Carefully, empty the water into the sink. Allow the ring stand
      set up and beaker to cool.
Chemistry             Lab: Effective Use of a Bunsen Burner                             3

   7. Re-light the burner, keeping the burner adjustment the same as the original
      adjustment. Move the ring clamp so that the wire gauze is at the top of the
      inner blue cone. Measure and record the distance at Test height #2 in cm.
   8. With a graduated cylinder, measure 100.0 ml of tap water into the cooled 250 ml
      beaker. Measure the temperature of the water. Record the starting temp. This
      temperature should be the same as the original water temperature.

   9. Repeat steps 3 through 6 from part II, for this new height. Be consistent about
       determining when the water is boiling.
   10. Clean up and put away equipment. Return the thermometer to the holder. If the
       burner, ring clamp, wire gauze and ring stand are too hot, leave them on the
       counter to cool. Wipe the counter with the sponge.
   11. Complete the analysis and evaluation.

Data Table 1: Quantitative (measurements)

Test Height Start temp of           Height of wire            Time to boil and Temp of
            water (°C)              gauze above burner              boiling



Data Table 2: Qualitative WATER (Descriptions and drawings)

Test Height          Before boiling         During heating         When boiling

Chemistry                  Lab: Effective Use of a Bunsen Burner                                           4

Data Table 3: Qualitative FLAME (verbal descriptions and colored picture)
Test Height             Flame before             Flame and set up
                                                 during heating



***Do the Analysis and Evaluation on your own paper and attach to this report.
        Typing this part is highly recommended.
Analysis: Use complete sentences.
   1. Why did you turn off the burner and cool the equipment between experiment
   2. Why is the height of the wire gauze the independent variable?
   3. Why is the time to boil the water the dependent variable?
   4. What observed differences did you note between the two heights?

 This section is done in paragraph form, using complete sentences.                       Avoid using
the words “it” and “they”. Use the proper nouns instead.

   1. Interpretation: what do the data and observations show; how was the problem
      answered; was the hypothesis correct, close to correct or very different.

   2. Evaluate the procedure and errors:
      a) Explain if and why the experiment works and/or why it doesn’t work. Some
             parts may work well, while others do not.
      b) Describe some specific sources of error.
      c) Explain how the errors influence the data.
      d) Explain which measurements were the least and most precise.
                        Instrumental error and human error exist in all experiments and should not be
                mentioned as a source of error, unless they cause a significant fault. Do not blame your
                lab partner.

   3. Suggestions for improvement of procedure:
           Describe what you would do differently if you were to repeat the
           experiment, to get better results. Be thorough and specific.

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