Science Buddies: "Ask an Expert"

Hi gusgus1229

Well I according to my research's, the iron is a catalyst of Luminol. Meaning Luminol is attracted to Iron.

Sincerely,
2shin7

Hi 2shin7,

Your research is correct: iron is one of the cations that acts as a catalyst for the luminol reaction. What that means is that iron (or copper) speeds up the luminol reaction without being consumed. This makes it so that photons are emitted rapidly enough by the reaction so that we can see it.

Hi Terik!

Well do you think that my partner and I can do some experiments with our topic and hypothesis?

THANKS!!!!!!!!!!!!!

Hi 2shin7,

Yes, I definitely think you and your partner can do some experiments to test your hypothesis, using some of the information I've provided in earlier posts.

HELLO Terik!

I have another question, is our experiment restricted??

Sincerely,
Shin

Hi Shin,
Can you please clarify what you mean by "restricted"?

Hi Terik,

By restricted I meant does it need to have an expert guiding us or no? like do we need forensic experts or chemists to be with us when we do our experiments?

Hi Shin,

The best thing to do is to talk with your teacher about the rules for your particular science fair. Generally speaking, I would not expect that you would need to have a qualified scientist with you when you do your experiments. However, since rules vary from fair to fair, you should check with your teacher about what the rules are for your particular science fair.

Hello Terik,

How can we use different amounts to prove that there is a difference?? Cause last Sunday we did some experiments and it didn't show much glow. Are we doing something wrong??

THANKSSSSS

Sincerely,
Shin

Hi Shin,

Will you please post a detailed procedure for what you have been doing, including the amounts of all chemical you have been using? Without knowing your detailed procedure, it's difficult for me to assess why what you are doing isn't giving you the results you expect.

Hello Terik

Our procedure is:
1. Set out materials and put on latex gloves
2. Set out five plastic cups in a row
3. Take the first cup, copper sulfate, luminol, hydrogen peroxide, measuring cups and camera into the dark room with lights on.
4. Pour 2 tsp. of copper sulfate into cup
5. Pour 3 tsp. of luminol into cup
6. have camera ready and light switch ready, and pour 3 tsp. of hydrogen peroxide into cup
7. Turn off the lights and wait for glow
8. Take pictures of the luminescence
9. Repeat steps 3-8 for cups ,3,4 & 5 but add 4 tsp, 6 tsp, 8 tsp, and 10 tsp
10. Compare luminescent result and the pictures taken
11. Analyze data and draw conclusion

If you need anything else please let me know.

Sincerely,
Shin

P.S. Thanks so much!

Hi Shin,

Did you get the "Cool Blue Light Experiment Kit"? The kit uses perborate as an oxidizer instead of hydrogen peroxide. If you did purchase the kit, did you do the recommended experiments described in the pamphlet that comes with the kit? Did those work?

Do you see any luminescence at all, even for a very short period of time? It looks like you are using rather large quantities of each chemical, and a high ratio of copper sulfate to luminol, which could make the reaction go to completion really quickly. (Notice that the procedure for this this Project Idea uses grains of copper sulfate).

If you still have materials left and you were able to see luminescence for brief period of time, I would try reducing the amount of copper sulfate that you add. Does that give you better results?

Hi Terik

Instead of perborate we used Hydrogen Peroxide, do you think that the hydrogen peroxide is making it glow less?
How are we going to analyze our results using a data table with numbers? And yes we got the "Cool Blue Light Experiment Kit." We did a similar experiment from the pamphlet, experiment 5.

Hi Shin,

You will get the best results if you use the chemical that came in the kit, so try using the perborate instead of hydrogen peroxide.

With regards to a data table, yes, you can compile your data and present it in a data table.

Hi Terik

Do you think we will have enough perborate if we are doing the experiment in a higher scale? Or should we buy some more? cause we've spent more than 50 bucks for the copper sulfate and more luminol powder and the kit. Do you think that we can add a little hydrogen peroxide into perborate or will we explode if we do that??? (Sorry I'm trying to think big here!)

Sincerely,
Shin

P.S. Sorry about my exaggeration and also I might ask more questions because my partner and I haven't talked about our questions for you...

P.P.S. THANKS A BUNCH!!!!!!!!!!!!!!!!!!!!!!!!

Hi Shin,

Feel free to keep asking questions. It's why we're here.

Have you been having any luck with the experiments? (That is, are you seeing luminescence?) Did experiment #5 from the pamphlet work?

I don't understand why you need to be doing experiments at a larger scale, using such large quantities of reagents. You're right - that get's expensive. You can scale down the quantities of reagents you use and still do the same experiments. I suggest doing that.

Avoid mixing perborate and hydrogen peroxide. Use the perborate that came with the kit to do the experiments. If none of your tests have produced luminescence, then don't do more tests until we can troubleshoot that problem (so that you don't waste reagents).

Hey Terik,

Ahmm well we already bought the more materials and before we did that we kind of decide to just use Hydrogen Peroxide and I think we are just going to stick with it since we have the materials already but we won't like do higher scale. We wanted to do your suggestion but sadly we already have the materials and we would not want to buy more Perborate because we think that it's kind of late already and we need to do our experiments ASAP. Thanks for your suggestion though.

We kind of did experiment 5 but we did it in a higher scale and we used Hydrogen Peroxide instead of Perborate. It just glows for about 3 seconds and then stops glowing. Do you think it is because we're using Hydrogen Peroxide the Luminol subsides and stops glowing?

And also we were wondering how we will record a data with numbers using our experiment?

Sincerely,
Shin

P.S. Sorry for delay of reply, I couldn't reach my partner and she was sick all week so this is the only time I reached her and actually got to talk to her regarding our experiment and some questions we have for you.

P.P.S. please tell me if I'm too formal, I'll make my tone more casual... Its just that you're a Planetary Scientist and we have a lot of respect for scientists.

P.P.P.S. THANKS SOOOO MUCH YOU HELPED US A LOT!!!!!!!!!!!!!!!!!!!!!!!

Hi Shin,

The good news is that you have done some experiments and you get luminescence. Yeah!

The luminol will always stop glowing eventually; your finding probably isn't a consequence of using peroxide. It stops glowing when all of the limiting reactant has been consumed in the reaction. The copper is also quite important because the copper catalyzes the reaction. That is, copper makes the luminescent reaction happen at a faster rate, without being consumed during the reaction itself.

Although it sounds like your project is slightly different, the measurement procedure outlined in the original Project Idea would be a good way to make some measurements. You can use a stopwatch to measure how long the luminescence lasts and then a digital camera to assess relative brightness. That said, don't be terribly disappointed if you don't see very much variation in brightness and duration as you change the amount of copper you are adding. If you don't see much of a change, then the project is not a failure! We can chat about how to move forward if all of your experiments turn out the same.

Hi Terik,

But what if there is no glow at all is that a good thing or a bad thing for our experiment? And also for our data table do we have to substitute and do guess and check for a data number? And also should we conduct an experiment comparing the luminescence of hydrogen peroxide and peroxide?

Sincerely,
Shin

Hi Shin,

Hmm...I'm confused. I thought you were seeing a glow for 3 seconds when you did an experiment that used hydrogen peroxide? But, now it sounds like you're saying that you don't see a glow. Please explain when you are (and are not) seeing luminescence during your tests. **The more detail you provide, the better I will be able to help you.**

The goal of your project is to test your hypothesis, so the experiments that you do should address your hypothesis. Your hypothesis describes the relationship you expect to see between the independent and dependent variables in your experiments. Based on your previous posts, your hypothesis isn't about peroxide vs. perborate, so, no, I don't think you need to do an experiment comparing the two. However, make sure that you stick to using only one of these reagents in your tests (Either do all of your experiments for the project using peroxide or all of the experiments doing perborate; don't switch back and forth when you are doing the actual experiments for your project.)

From your earlier posts, it sounds like your independent variable is the amount of copper sulfate you are adding and your dependent variable is the luminescence. Am I correct about that? Or are your variables different from that? If you want to measure the effect of the copper sulfate, then you need to decide on the amounts of peroxide and luminol mixtures you will use. Don't change those amounts as you do your experiments. Use the amounts suggested in the Cool Blue Light of Luminol Project Idea or in experiment #5 in the pamphlet, for example. Then, do experiments varying the amount of copper sulfate that you add. The reaction is VERY sensitive to the copper sulfate, so I suggest varying the number of grains of copper sulfate you add. Using teaspoons is too imprecise and adds too much copper sulfate. Start with 10 grains of copper sulfate and see if you get a good result. You could then try 0 grains of copper sulfate (as a control), 3 grains, 6 grains, 12 grains, and 15 grains. See what types of results that gives you. (NOTE: I'm assuming the grains of copper sulfate you have are the same as the sizes of grains that come in the Cool Blue Light kit.)

Please don't forget to respond to my questions in the first paragraph - doing so really will help me help you better!

Hey Terik,

Well when we put the hydrogen peroxide mixed with luminol and then put the copper sulfate, it didn't have any Luminescence. I was wondering why. And also when we put the copper sulfate first and them mixed it with luminol and then put the hydrogen peroxide and then that was the time that it glowed for 3 secs. But my question is that why do we need to change the order of our previous experiment just to see a three second glow? and why are can't we get enough proof and enough Luminescence for our board? I just don't get how we put different amounts of copper sulfate and same amounts of hydrogen peroxide and luminol and kept getting the same glow we got from other tests.

And yes you are correct with our independent and dependent variables. So do we have to change the amounts of luminol and hydrogen peroxide with the same amount of copper sulfate we will use? or is it not necessary? And so we can't do the peroxide vs. perborate thing? do you think the judges wouldn't like it if we did that? or we could do that but we need to change our hypothesis and question to make it possible? should we make a data table with a guess and check number because we need a data with numbers?

Thanks!

Sincerely,
Shin

Hi Shin,

To get good results, you should mix the copper sulfate with the luminol, then add the hydrogen peroxide. You need the copper to catalyze the reaction in order to make it bright enough so that you can see it. These should be some of your controlled variables - always mix the ingredients in this order, and always use the same amounts of hydrogen peroxide and luminol powder. The only thing that should change from test to test is the number of grains of copper sulfate you add: the amounts of the other ingredients should stay the same, and the order you mix ingredients together should stay the same.

Judges like projects that clearly identify an independent variable, a dependent variable, and then do experiments that interrogate the relationship between those two variables. Hence, you do not need to do any experiments changing the amounts of luminol or hydrogen peroxide. Those experiments would assess the effect of a different independent variable than you are interested in. You also do not need to do comparisons between experiments done with peroxide vs. perborate. Again, that would test a different independent variable than the one you are interested in.

With regards to your data table, you shouldn't need to do any guess and check numbers. (I'm actually not sure what you mean by that, in this case.) You can make a data table that has a separate row for each number of grains of copper sulfate you add (e.g., a row for 0 grains, 3 grains, 6 grains, etc.). Then, you can have two columns for each trial that you run (a total of six columns, if you do three trials). Remember that you need to run each experiment multiple times to assess variability; three times is the standard number of replicates for school science fair projects. Label one of the columns in the data table for each replicate "time (in seconds)" and the other "brightness". Then you can record how long you can see the glow (measured in seconds) and the brightness of the reaction (measured as described in the Cool Blue Light of Luminol Project Idea). If you aren't measuring the brightness of the luminescence, then you don't need to have those columns. You would only need the columns for how many seconds the luminescence lasts. Filling out that data table should give you enough data for your board.

The fact that you are seeing the same glow in all of your tests (even with different amounts of copper) isn't particularly surprising to me. (But, make sure your measurements you make of the duration of luminescence and brightness actually support this conclusion!) It might seem like a disappointing result to you, but it actually reveals something fundamental about the way luminescence is produced in this reaction. It's a really neat results! Take a look at the "Background" section of the Project Idea - what is the role of copper (or iron) in the reaction? That's a clue to what's happening in your experiments.

Hey Terik,

I'm so sorry for the late reply, I usually get notifications from sci buddies regarding this topic but surprisingly I didn't get any notification for this reply. So in that case even though we use different amounts of copper sulfate it doesn't matter? because we will not have the glow that we are expecting? And also by guess and check I meant, that we will use random numbers and then check if it will work. I really don't have a lot of questions for you today since we're not pursuing our county form. Maybe if we (my partner and I) will have time to do our experiments during Thanksgiving break.

I hope it is ok with you if I ask more questions or even write to you during Thanksgiving break.

Thanks!

Sincerely,
Shin

Hi 2shin7,

I apologize for the delayed response - my wife gave birth to our new baby girl on Monday, so I've been wrapped up with preparing for/enjoying my new baby girl.

I would expect you to see some glow, like you did when you saw the 3 second glow when you did the experiment from the pamphlet. But, yes, I don't expect that you will see a strong dependence on the amount of copper sulfate you add. This is because the copper acts as a catalyst, which means that the copper ions participate in the reaction, but do not get used up in the process.

For more information about that, check out the "luminol chemiluminescence", "Light emission from 3-APA", and "Movie of Luminol Chemiluminescence" sections of the followig website. It's written at an introductory college level, so please let me know what questions you have about it. I'm assuming that you have taken (or are taking) high school chemistry.

You can certainly ask more questions; I will probably be a bit slower to respond for the next couple of weeks, but by the Monday after Thanksgiving, I should be back to normal.

Hey Terik,

First of CONGRATULATIONS!!!!!!!!!!! I'm happy for you!

I'm sorry, but I don't take high school chem. I'm only an 8th grade. I really don't know which website to click because there's like a lot popping out whenever I type the things you suggested for me to visit. So the copper sulfate wouldn't really give us much glow? So it will just glow or about 3 seconds. Do you have any suggestions for us to do, so we can keep the glow going for a longer time span? to be honest I'm really disappointed with the results because we were expecting more.

I don't really have any problems with you responding late. I hope you have fun with your new baby! Enjoy! Answer whenever you want. Take your time with your family.

Sincerely,
Shin

P.S. I'm curious... what's her name?

Hi Shin,

Oops! I forgot to post the link to the website I mentioned. Here it is:

http://chemwiki.ucdavis.edu/Physical_Ch ... minescence

It might be a bit too advanced because it assumes you know high school chemistry. So, don't stress out if you don't understand parts of the article. If you want to make the glow last longer, you can try refrigerating the hydrogen peroxide. Lower temperatures will make the reaction last longer - note, however, that it will also lessen the brightness of the glow because the reaction will happen more slowly.

Hey Terik,

Ahmm the website you gave me, I actually visited that before for a source. But since I couldn't understand anything from it I didn't use it as a source. And now that I re-read it... (sad to say) I really can't understand any of it.

The only vocabularies I understood was Luminol Chemiluminescence and Chemiluminescence Reaction.

I tried my best to understand it but my brain can't find anything that could lead to other vocabs...

Sincerely,
Shin

Hi Shin,

Ok, let's see if I can put this into some simpler terms. Making luminol glow is a bit like baking cookies. When you make cookies, you add a bunch of ingredients, mix them together, and - eventually - you have the result: cookies. For cookies, you use ingredients like flour, sugar, and eggs. For the luminol reaction, you use peroxide and luminol as "ingredients". The result is (among other things) the glow you see. The glow is like a cookie.

Now, sometimes when you make cookies you might mix them by hand. This takes a lot of work and can take a long time. Other times, you might use a machine to help you mix the cookies. You can make cookies faster and easier that way. The mixer is a catalyst for making cookies. The copper sulfate is kind of like the mixer - it doesn't change the ingredients or recipe you need to "make" the glow. But, adding the copper sulfate makes the reaction happen a lot faster. The copper acts as a catalyst.

Because the copper isn't an ingredient in the luminol reaction, you don't need very much of the copper to be present - you just need some. Consequently, changing the amount of copper won't have a big effect (until you get to really small amounts). The result that (I think) you are getting isn't boring . Instead, that result reveals how catalysts work. They do not get used up in reactions, but they make it easier for a reaction to occur, which makes the reaction happen more quickly.

Hey Terik,

Tbh, I don't have a clue about this project but I'm trying to research things about this project. I mean we're only 8th grades to understand these stuffs which is like a very high learning stuff. Do you think that this project is really hard for us? I don't want to make my partner do everything. I'm sorry if I'm being annoying. I just want to know everything about this project, like if this project will have the results that we are expecting right now. I just want to know if we are spending tons of money for a worth it project. Should I go to another resource? and find more there? Because tbh I'm having a really hard time. I'm so sorry I'm very dramatic. Thanks so much for all your help.

Sincerely,
Shin

Hi Shin,

Hmm . . . it sounds like you're feeling a little bit frustrated with the way your project is going. I've worked on science projects that I've found frustrating before, so if you're feeling that way, I empathize with you! Let's try this: I put a note out asking another Expert come take a look at the questions you have. Hopefully that person will have some new ideas or suggestions that will be helpful for you!