How to Use a Bunsen Burner (And More)

Which part of the flame is hottest?

Today we had a lab session and we had to find out which part of the flame (from the bunsen burner) is the hottest. My lab partner and I had hypothesized that the inner blue core of the flame would be the hottest since it was nearest to the core, meaning it should have a higher temperature.

But of course to even start the experiment, we had to learn how to use the bunsen burner SAFELY.

So here are the steps:

1. Connect the rubber tubing to the gas tap
2. Check that the air holes are closed (*Leaving air holes open could be dangerous)
3. Turn the gas tap on
4. Position the lighter above the barrel and light it up
5. Adjust the gas tap accordingly
6. Open the air holes to about halfway

And ta-da! There you have it, a working bunsen burner. To turn it off, close the air holes, then turn off the gas tap.

*Leaving the air holes open when lighting up the bunsen burner could result in a strike back. You don't want to know what it is, but it could be dangerous. So don't do it.

Anyways, back to the experiment...

So to test which part of the flame would be the hottest, we had divided the flame into three parts: the outer orange/yellow flame, the outer blue flame and the inner blue core. Below are the steps we took:

1. Turn on bunsen burner

2. Use metal tongs to hold copper wire at the centre of the orange/yellow part of the flame

3. Use a stopwatch to time how long it takes for the copper wire to glow red

4. Record the time

5. Repeat steps 2-4 with the copper wire held at the outer blue flame and the inner blue core.

And this is our results...

From the results tabulated above, we can see that the copper wire heated up fastest at the outer blue flame. In other words, this means that the hottest part of the flame is actually at the outer blue flame, so our hypothesis had been wrong.

Reflections...

After completing the whole experiment, there was one thing I was curious about. Why did we use a copper wire and not any other wire, or even sewing needles! Apparently, this is because copper is an excellent conductor of heat due to Metallic Bonding, and the fact that it's valence electrons are loosely arranged. Interesting...