Sunday, February 21, 2010

Kid's Science - Carbonic Acid

While researching last week's Science Sunday experiment, I came across a couple of experiments, dealing with carbonic acid, that I thought would be fun to try out with the kids, today.

Carbonic Acid (H2CO3) is a combination of water (H2O), and carbon dioxide (CO2). It is also what causes that slightly uncomfortable, tingling sensation on your tongue when you sip your soda pop. We experienced this for ourselves, with an experiment from Education World.

I gave each of the children a small cup of pop (they are always interested in soda pop science, because we don't normally give them pop to drink), and then timed them to see how long they could hold their tongues in the liquid. It proved to be a very difficult challenge!

We used pH paper to test the acidity of Coke Zero. Not surprisingly it showed high acidity. What was surprising though, was our flat soda, one of Daddy's old ones we pulled out of the fridge :), was also quite acidic, though the flat soda didn't hurt the tongue. After checking the ingredients on the side of the can, we decided this was due to the presence of the phosphoric acid (also what makes Coke a good rust remover!).

Keeping our findings above in mind, we moved on to another experiment we found on the website of Wind Cave National Park. This time, we tried to make water acidic by adding carbon dioxide to it. Where did we get the carbon dioxide?

If there's one thing we learned from watching Apollo 13, last night, it's that people breath out carbon dioxide!

Following the instructions of the experiment, we tried blowing through a straw, into a glass of water for one minute, and then testing the acidity of the water with pH paper. We tried it with cold water, and warm water. We tried it with a full glass, and with an almost empty glass. And we tried it with one person blowing into the glass, and with two people blowing into the glass. But, we couldn't seem to make carbonic acid. Our pH papers looked just the same before, during, and after we blew into the water.

This was disappointing, but it did give us a chance to discuss the fact, that there are a number of variables, that can effect the outcome of an experiment. Were our straws too big? Were we blowing too vigorously? Did the water need to be warmer? We used filtered water, instead of distilled water, would that make a difference? Hmm...we have a lot to think about.

In the meantime, you can find a number of other fun, and hopefully successful, science experiments, and projects for children, at this week's Science Sunday link up, hosted by Adventures in Mommydom.

It's great to be a homeschooler.


Natalie PlanetSmarty said...

Your older ones seem to be highly entertained by this experiment. Too bad that you couldn't make water acidic enough, but maybe your PH paper is not sensitive enough. I also think that it might have to do something with pressure, because I think they make pop under pressure. Anyway - fun.

Michelle Gibson said...

This looks like it was a lot of fun. You asked some very good questions, too! Great job! I am really enjoying your experiments. =)

Ticia said...

The pictures of them trying to hold their tongues in the soda cracked me up.
I always love seeing your experiments.

Jamie said...

Wow, that was a great post. I'm always looking for fun sciece experiements, Ethan loves them. You can tell your kids were enjoying it. That's the way to learn.

Debbie said...

Great experiment. Something for some more investigation. Did you dip your test strips directly into the glass? Maybe if you drop the water onto the test strip with a dropper you will have different results??

Emma said...

If you can get hold of some pH indicator put a couple of drops into the glass of water first and then get the kids to blow through the water with the straws. The water should change from green (neutral) to red (acidic) in front of their eyes! (Note: Cut a small hole in a piece of clear plastic and pop it over the top of the cup to avoid vigorous blowing accidents!)