Lesson focus: Heating is useful only when the energy transfer is controlled and observed safely.
Identify the parts of a Bunsen burnerA gas burner used in the lab, with an air hole you can adjust to change the flame. and describe safe heating practice.
Build on earlier learning
Laboratory equipmentRevisit how apparatus is selected and handled to obtain useful measurements.
Practical
Heating safely with a Bunsen burner
- Stand the Bunsen on a heatproof mat, tie hair back and wear eye protection.
- Close the air hole, light the splint, then turn on the gas: this gives the visible yellow safety flame.
- Open the air hole for a blue roaring flame when heating; the hottest region is just above the tip of the inner blue cone.
- Heat liquids gently in a boiling tube held at an angle with a holder, pointing away from people.
Record: Note which flame is used for each step and why.
Safety: Return to the yellow safety flame whenever the burner is not being used.
You will be successful when you can…
- Identify the gas inlet, collar, air hole and barrel.
- Sequence lighting and shutting down safely.
- Select the safety or heating flame for the task.
- Connect each control measure to the hazard it reduces.
Words that carry the science
- Bunsen burner
- A laboratory gas burner with a controllable air supply.
- air hole
- Opening that controls how much air mixes with the gas.
- safety flame
- Visible yellow flame used when not actively heating.
- heating flame
- Hotter blue flame used for controlled heating.
- heatproof mat
- A surface that protects the bench from heating equipment.
Control a Bunsen burner safely
01Control the gas–air mixture
Gas enters through the inlet and travels up the barrel. Turning the collar opens or closes the air holeThe hole at the bottom of a Bunsen burner that you open or close to let more or less air mix with the gas., changing how much oxygen mixes with the gas before burning.
With the air holeThe hole at the bottom of a Bunsen burner that you open or close to let more or less air mix with the gas. closed, incomplete combustion produces a luminous yellow safety flameThe yellow flame of a Bunsen burner, made with the air hole closed, which is easy to see when not heating. that is easier to see and cooler. Opening the air hole produces a non-luminous blue heating flameThe hot blue flame of a Bunsen burner, made with the air hole open, used for heating things.. With more oxygen, the gas burns completely, so the flame is hotter and makes no soot.
02Use a safe sequence
Place the burner on a heatproof matA mat placed under a Bunsen burner to protect the bench from heat., check the hose, clear the area and tie back hair. Close the air hole before lighting. Light the splint first, hold it near the top of the barrel, then turn on the gas.
Use the yellow flame while waiting. Open the air hole only when ready to heat, and never leave a lit burner unattended.
03Treat hot equipment as hot
Glass and metal may look unchanged when hot. Use tongs or allow time to cool, and keep test-tube openings pointed away from people.
Heating a sealed container can increase pressure dangerously. Unless a specific supervised method says otherwise, containers must not be sealed during heating.
The order reduces the chance of escaping gas, burns and unnoticed flames.
- PrepareGoggles on, hair tied, bench clear, hose checked.
- Close air holeStart with the visible yellow-flame setting.
- Light splintCreate the ignition source before releasing gas.
- Turn on gasIgnite promptly at the top of the barrel.
- HeatOpen the air hole for a blue flame only when ready.
- FinishClose the air hole, turn off gas and allow equipment to cool.
Bunsen burner flames
Turn the collar to open the air hole. More air mixes with the gas, so the fuel burns completely: the flame turns blue, gets hotter and stops making soot.
Controls
Temperatures are approximate. Always light the burner with the air hole closed.
Improve an unsafe method
A student turns on the gas, searches for a splint, then lights the burner with the air hole open.
- Identify escaping unburned gas as a hazard.
- Prepare and light the splint before turning on the gas.
- Close the air hole so the burner starts with a visible yellow flame.
- Open the air hole only once the burner is lit and heating is about to begin.
How to make the reasoning visible: Name the precise unsafe step, then replace it with a control measure that changes the procedure.
Heating decision check
Decide on the correct response for each situation.
| Situation | Hazard | Control |
|---|---|---|
| Long hair near flame | Hair may ignite | Tie it back before lighting |
| Cracked test tube | May break when heated | Replace it; do not use |
| Hot tripod after flame is off | Burn from stored thermal energy | Allow to cool or use tongs |
| Test tube pointed at a partner | Hot liquid may eject towards them | Point opening away from everyone |
Why should the air hole be closed before you light the Bunsen burner?
A student with long, loose hair says, “I’m wearing goggles, so I’m safe.” Why is this not enough?
Look at the table. Why should a cracked test tube not be heated?
Check your understanding
Answer from memory, then check against the suggested answer.
What does the air hole control?
Which flame do you use while you are waiting?
Why must you be careful with glass after heating it?
What colour is the safety flame?
What should the Bunsen burner stand on?
A student stops heating for 30 seconds to write down a result. The burner is still lit. What should they do to the flame, and why?
Opening the air hole makes the flame blue and hotter. Explain why.
Why is the yellow flame easier to see than the blue flame, and why does that make it safer when you are not heating anything?
Exam Question Practice
Exam Question Practice
Mark points shown after marking
Describe one thing you should do to get ready before lighting a Bunsen burner.
(1)Describe how to light the burner. Say what you light first, the splint or the gas, and where you hold the flame.
(2)The air hole is closed at the start. Explain why. Start: “A closed air hole gives a … flame, which …”
(1)Total for this question: 4 marks
Command word: For describeA command word: say what happens or what something is like, step by step, without needing to give reasons., give the steps in order. For explainA command word: say how or why something happens, giving reasons with words like "because" or "so"., give a reason, using “because” or “so”.