Electrolysis w/ My Kids - We are stumped

In summary, the speaker's son is preparing for 2nd grade and the speaker tries to keep his education going throughout the year by doing experiments. They did an experiment with electrolysis to make hydrogen gas and observed unexpected results. They also tried the experiment with iodized salt and baking soda, resulting in blue and green colors. The speaker is curious about the chemistry behind the reactions and asks for help. They also mention using distilled water or tap water and the presence of impurities affecting the results.
  • #1
Justinmcg67
14
0
Hello all! My son is getting ready to go into the 2nd grade here on Wednesday and although he takes breaks during the summer, I really try to keep his education rolling throughout the entire year. As such, I try to get him excited by doing experiments and other things to captivate him and get him anxious for the school year. While I had some spare time I researched some simple experiments at home. The one that sounded the most interesting as far as all the science taking place, was electrolysis. Specifically we wanted to make hydrogen gas and check out the bubbles forming. Many interesting and unexpected (but good!) things happened. Also, I will link videos (on YouTube) taken from our experiments.

First the set up is as follows:
- Copper Wire Electrodes x2
- AA Rechargable Batteries x5 (7.5V total)
- Mason Jar
- Non-Iodized Salt
- Water (Boiling when added)
- Vinegar

The first thing we got was as expected. A clear solution with bubbles forming and one electrode turning darker. I presumed the darkening to be the copper oxidizing, as in what happens to pennies over time. A video (in 1080p) is linked below to add clarity:
Link

One thing was that despite the instructions from About.com and other places (Instructables.com, etc.) we got results that were not listed. The observation we got was a red/brown almost salmon-like color in the solution. A video (in 1080p) is linked below to add clarity:
Link

As the process went on longer it got much more red/salmon-like and presented obvious flakes, or chunks that didn't seem to be stable, as in like paper when it stays in water for long period of time. A video (in 1080p) is linked to add clarity:
Link

Having looked into the experiment and its safety I noted that the solution is basic and needs to be neutralized in order to be disposed of properly (not to sure if this is accurate, but did it anyway as a caution). As such we added vinegar, and to our surprise the solution went clear with only the chunks or semi-pieces left. Most eventually settled to the bottom. A video (in 1080p) is linked to add clarity:
Link

Now what I would like to know is: Why does the copper dissolve? And, more importantly, is there chemistry that can be explored here? :bugeye: Can we do something with the solution?

Additionally, we did this same experiment and used iodized salt, and got the same results. We also tried using baking soda instead of table salt (read that this was a more safe form of the experiment). A video to that will be linked to as well. For the baking soda we wanted to know why the solution turned blue/teal? We noticed how similar one copper lead was turning green similar to that of the Statue of Liberty, while the other turned black. This seems obvious, but if anyone wants to break down the chemistry that would be great! (Video link below)
Link

Any and all help is much appreciated! Thanks! :biggrin:


TL;DR

Why does copper dissolve via electrolysis in a solution of table salt and water?
 
Last edited:
Chemistry news on Phys.org
  • #2
I am not convinced it was copper dissolving. Have you used distilled water or tap water? Is your water iron free?

I suppose the copper was just some copper wire - as such it may contain some impurities that make the experiment result difficult to predict and explain.

Blue color is that of copper aqua complex (that is, Cu2+ complexed by water molecules). Green solid is a basic copper carbonate - hard to tell what is the exact composition, as it is variable and depends on conditions.

There are two important differences between both solutions - one is that bicarbonate has a much more stable pH, the other is that presence of carbonates makes the precipitation of the basic carbonate possible. Typical tap water contains some carbonates as well, but the amount is much lower.

Great experiment BTW :smile:
 

1. What is electrolysis and how does it work?

Electrolysis is a process in which an electric current is used to drive a non-spontaneous chemical reaction. In our experiment, we are using the electric current to break apart water molecules into hydrogen and oxygen gas.

2. What materials do I need for this experiment?

You will need a battery, two pencils, two alligator clips, a cup of water, and salt.

3. How do I assemble the experiment?

First, sharpen the ends of the pencils and insert them into the alligator clips. Then, place the pencils into the water, making sure the clips do not touch. Add a small amount of salt to the water. Finally, connect the alligator clips to the battery to create an electric current.

4. What are the products of electrolysis?

The products of electrolysis are hydrogen gas at the negative electrode and oxygen gas at the positive electrode. These gases can be collected and tested with a flame or used in other experiments.

5. How can I make this experiment more challenging?

You can try changing the concentration of salt in the water, using different types of batteries, or adding other substances to the water to see how they affect the electrolysis process. You can also try using different types of electrodes, such as copper or zinc, to see if they produce different results.

Similar threads

Replies
4
Views
1K
  • Chemistry
Replies
1
Views
7K
  • Chemistry
Replies
1
Views
1K
Replies
16
Views
2K
  • General Discussion
Replies
8
Views
3K
Replies
27
Views
24K
Replies
3
Views
17K
Back
Top