A Bunsen burner is a common laboratory tool used to produce a steady, controllable flame for heating chemicals and equipment. It works by mixing a fuel gas with air before combustion, which makes the flame hotter and cleaner than a simple yellow safety flame. Understanding the parts of the burner helps students adjust it correctly and recognize safe operating conditions.
The shape and color of the flame give important clues about temperature, oxygen supply, and combustion quality.
Gas enters through the gas inlet and passes through a small gas jet, where it speeds upward into the burner barrel. Air is drawn in through the air hole near the base, and the collar controls how much oxygen mixes with the gas. With the air hole open, the burner produces a blue flame with an inner cone and a hotter outer region just above the cone tip.
Safe use depends on lighting the burner correctly, keeping flammable materials away, and choosing the right flame for the task.
Key Facts
- Opening the air hole increases oxygen mixing and usually produces a hotter blue flame.
- Closing the air hole reduces oxygen supply and produces a cooler yellow safety flame.
- The hottest region of a blue Bunsen flame is just above the tip of the inner blue cone.
- Complete combustion of methane: CH4 + 2O2 = CO2 + 2H2O.
- Incomplete combustion can form carbon monoxide and soot when oxygen is limited.
- Always light the burner with the air hole mostly closed, then adjust the collar to obtain the desired flame.
Vocabulary
- Bunsen burner
- A laboratory burner that mixes fuel gas with air to produce a controllable flame for heating.
- Air hole
- An opening near the base of the burner that allows air to enter and mix with the gas.
- Collar
- The adjustable ring that opens or closes the air hole to control the oxygen supply.
- Inner cone
- The smaller blue cone inside a properly adjusted flame where gas is still mixing and beginning to burn.
- Complete combustion
- A reaction in which a fuel burns with enough oxygen to produce carbon dioxide and water.
Common Mistakes to Avoid
- Heating glassware in the inner cone only, because the hottest region is actually just above the tip of the inner cone in the outer flame.
- Leaving the air hole fully closed during heating, because this gives a cooler yellow flame that can deposit soot on equipment.
- Opening the gas tap before having an igniter ready, because unburned gas can collect and create a fire or explosion hazard.
- Pointing test tubes at yourself or classmates while heating, because hot liquid can suddenly boil over and spray out of the tube.
Practice Questions
- 1 A burner heats 150 g of water from 22°C to 72°C. Using q = mcΔT and c = 4.18 J/g°C, how much heat energy does the water gain?
- 2 Methane burns according to CH4 + 2O2 = CO2 + 2H2O. How many moles of O2 are needed to completely burn 3.0 moles of CH4?
- 3 A student sees a tall yellow flame that leaves black soot on a beaker. Explain what burner adjustment should be made and why it changes the flame.