Chemiluminescence

So last week I happened to take over part of the English teacher’s class while she had to step out. My class was occupied with their own work so I gave the high schoolers an option. Help me make posters (anchor charts) that I haven’t had time to make, or do some impromptu science and make your own glow sticks. It was absolutely hilarious watching them look at each other with the ‘I don’t know what do you wanna do’ looks on their faces. I could see that they both wanted to do the glow sticks but neither wanted to admit it. They really wanted me to tell them to do one or the other so that they could grudgingly agree. When I didn’t they didn’t know what to do. So they looked at each other until one finally said, “You wanna do glow sticks?” and the other responded, a little more quickly than she had meant to, “Oh ya good I wanted to do that too.” After she said it she tried to play it off and I knew that she had not meant to show such enthusiasm but I was glad to know they were excited.

So I got them set with gloves and glasses and we papered the table. We got weighing paper and the chemicals and my digital scale and I gave them a list of weights. First I asked if they knew how to use the scale. “Yaaa. We Know!” was the response. Then after about a minute I showed them how to turn it on, zero it and switch to the correct units. They measured out the chemicals which are listed below for those who are interested in such things.

.2g luminol;

24g Sodium bicarbonate (baking soda)

4g Sodium carbonate (baking soda spread thin in a tin pan and cooked for an hour at 200F in an oven)

.5g ammonium carbonate (bakers ammonia) which smells really strongly and I think is the stuff in smelling salts.

Then there was another conversation as to how to measure liquids and mL and converting Liters to mL since the graduated cylinder only had mL not L. We added the above list to 1000ml (1L) of water from our filter.

Then in a separate container we added 50mL 3% H2O2 (hydrogen peroxide) and then we were just about ready.

Now you are supposed to have copper sulfate but the reaction is possible if you place the drops on a copper surface like that of a penny. The other problem we had was that the luminol was fairly old and there was some question if it was any good anymore. And the high schoolers also mentioned that they were not entirely sure of their measurements.

But we proceeded to try. We added a couple drops of each solution to the top of the penny (which we probably should have buffed first) and as feared nothing happened.

So that was a wash but I wanted them to get to see the glow since they had worked so hard so over the weekend I made a new batch with some newer luminol and with the copper sulfate (.4g) which I found in the chemistry teachers supply closet, and today a few of the high schoolers got to come down to my room and help pass out containers for my studnets with the understanding that they would also get to participate.

They measured roughly 30mL of luminol solution into water bottles and 30mL of the diluted hydrogen peroxide into a cup. And while the high schoolers were doing that my class had a discussion about molecules and reactions.

Each student got to wear gloves and safety glasses and looked like real scientists. They had a bottle, a cup and a funnel on their desk. The high schoolers got to do theirs first and then I went around and held the luminol bottle down on their desk as each student added the hydrogen peroxide. By the time we got through all of them the ones we started with were pretty well out but it was still cool to see all the desks glowing blue and to see the fascination of the kids (even the older ones).

At the very end of the day I took what was left of the luminol and set some aside for the high school science teacher and added about 250mL to a round bottom boiling flask. This then was the motivation for the kids to get cleaned up at the end of the day. If they were ready in time we would do this reaction using almost ten times the volume of what they had done.

We cleaned up and found a place at the carpet and I turned off the lights. I mixed the two solutions and stoppered the bottle. Part of our discussion was that reactions often result in bubbles so when the stopper popped off that was a good review point as to why. The bubbles which result from the reaction (in small amounts) are N2 (nitrogen gas) which is what most of the atmosphere around you that you breath is made from.

The procedure if you want to try.

How to turn baking soda into sodium carbonate

All the materials needed can be obtained from Amazon and or eBay. Luminol is probably the most costly at about $20/g but remember that a gram is enough to do what I did 5 times over, more if you are stingy on how much solution you give them. 1g luminol will make 5L of solution to be mixed with 5L of hydrogen peroxide solution for a final glowing volume of 10L. Not bad for the less than $30 all told.

IMG_6671IMG_6675

Luminol solution before and after mixing the H2O2. The glow lasted 1-2 minutes

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