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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 efficient? 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 water. 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 Procedure: 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 (cm) 1 2 Data Table 2: Qualitative WATER (Descriptions and drawings) Test Height Before boiling During heating When boiling 1 2 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 1 2 ***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 setups? 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? Evaluation: 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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