But Which Flame is Hotter?

The Bunsen burner has two types of flames – the yellow safety flame and the blue heating flame. This lab activity compares the two flames and tests which will allow 50ml of water to reach 80^oC in the shortest time.  The airhole at the base of the barrel controls the entry of air and therefore oxygen gas into the burner where it mixes with the gas, usually propane or butane. This gas is then ignited at the top of the barrel. By adjusting the collar, the amount of air that can be mix with the gas is also adjusted. An open airhole allows maximum air to be mixed with the gas and causes complete combustion and a therefore a clean burning, blue flame. When the airhole is shut incomplete combustion occurs due to the lack of air and a sooty, orange flame is the result.

Which Flame is Hotter Lab Learning Objectives:

• Compare the heating ability of the yellow and blue Bunsen flames.

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• 1-4 Vocabulary Activity SE - Lab Procedures (Doc)
• 1-4 Vocabulary Activity SE - Lab Procedures (PDF)
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• 1-4 Lab Activity TE - Lab Procedures (Member Only PDF)

Which Flame is Hotter Lab Materials:

• Bunsen
• Tripod
• Gauze mat
• Heat proof mat
• Beaker with 50mL water
• Thermometer
• Clamp stand
• Stopwatch

Lab Procedures:

1. For this lab you will need to work with another group to obtain answers. One group will use the blue flame for heating while the other will use the yellow safety flame.
2. Set up the equipment as is seen in the diagram below.
3. Light the Bunsen burner. If you are the group using the yellow flame, then keep the air hole closed for the whole experiment. Otherwise open the air hole to obtain a blue flame before starting the experiment.
4. Measure the initial temperature of the water and record this value.
5. Start the stopwatch and measure and record the temperature of the water each minute until 80^oC is reached.
6. Swap answers with another group so that you have two sets of data, one for each type of flame.

Which Flame is Hotter Lab Procedures Observations:

Hypothesis

(Make a prediction about which flame will heat the water the fastest):

Results:

1. Complete the table

2. Draw a line graph of the results for each test. 

Lab Procedures Post-lab Questions:

Answer the following questions:

1. Which flame was the hottest?
2. Once the beakers have cooled down, lift each one and check the underside. What do you observe?
3. Which flame is easier to see?
4. Why is it important to light the burner with the airhole closed?
5. What is the purpose of the gauze mat in this experiment?

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Lab Procedures PDFs

• • 1-4 Assignment SE - Lab Procedures (PDF)
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  • 1-4 Guided Notes SE - Lab Procedures (PDF)
  • 1-4 Guided Notes TE - Lab Procedures (Member Only)
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Unit 1 – Lab Skills

• 1-1 Lab Equipment
• 1-2 Drawing Scientifically
• 1-3 Lab Safety
• 1-4 The Scientific Process
• 1-5 Making Observations
• 1-6 Measuring
• 1-7 Planning an Investigation
• 1-8 Writing Up an Investigation

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