Shriveled Potatoes

So for Christmas Grandma gave us a book entitled 365 Science Experiments.  While flipping through the other day, I found a quick and easy one that we could do in an afternoon with no preparation.  It is experiment #64 "Shriveled Potatoes".

"Materials: 1 Potato, 2 Saucers, Chopping Board, Knife, Salt, Water"

You take two saucers (or small plates) fill both with tap water, and add salt to one of them.

Then you cut the Potato in half and put one half into each solution.

You then let it sit and absorb the water.  The book says you should see a difference after about 30 minutes.

30 minutes later, this is what our potatoes looked like.

The following morning, this is what our potatoes looked like.

So something went wrong.  Did we add an improper amount of salt?  It doesn't say how much, and I don't think you can add too--we saturated the solution.  I think perhaps why we didn't get the same results, is because we used red potatoes instead of of regular russet potatoes.  So as soon as we get through this bag of potatoes, we'll try again with a russet.  We'll let you know how it goes...

Independence Day

What better way to kick off Science Sundays, than by celebrating the birth of our nation? While browsing the internet for experiment ideas, I came across Soda Pop Fireworks (http://www.education.com/activity/article/Soda_pop_fireworks/). Since fireworks were banned for our apartment complex, and the surrounding neighborhoods, we decided this would be a great solution to having an experiment and celebrating Independence Day.

The movie was too big to post here, and rather than posting smaller segments of the whole, I decided to just create a YouTube account where I could post the videos and just post the links here.

Science Sundays' Inaugural Event: http://www.youtube.com/watch?v=fHyvQWDNvsg

So how does it work?

One source I found said that the only things that mattered were the carbonation in the soda, and the tiny pores covering the mint Mentos. These two combined caused a physical (not chemical) reaction releasing the Carbon Dioxide very quickly, causing the explosion. The narrow neck of the 2 liter bottle helps pressurize the system, making the reaction better. As you can see in the video, all types of soda tested worked okay. But why did some work better than others? There's got to be something more than just the carbonation.

According to MythBusters (http://en.wikipedia.org/wiki/Soda_and_candy_eruption), specifically referring to Diet Coke, the caffeine, potassium benzoate, and aspartame also contribute to the reaction. Also the gelatin and gum arabic of the candy is important. You can read about all the details yourself, I'll just mention some of my own observations.

The Club Soda, did indeed erupt, supporting the idea that only carbonation is needed to react with the candy. However, the Cherry Soda's reaction was much better, suggesting the involvement of another ingredient. I haven't looked at the ingredients on the Cherry Soda, so I have no specific idea, but there is definitely something else at work. Now the Mountain Dew also reacted better than the club soda, but not as well as the cherry soda. What would explain that? Again, I haven't looked into the ingredients to form a guess--just observing. The other four bottles were all diet soda, and they reacted the best. This suggests that the aspartame is a large contributer to the reaction. I would argue against MythBusters claim that caffeine is important though. The last two bottles we tried were Caffeine Free Diet Coke, and they reacted the same as the Lime Diet Coke, and the Diet Dr. Pepper. I don't think caffeine has anything to do with it. As far as the rest of the ingredients are concerned, I don't know enough about them to comment.

In summary, Mint Mentos are important. Although we didn't try anything else, we'll believe the claim that only they work.

Carbonation is also crucial to the reaction. Again, we did not demonstrate this, but if the sodas were left opened for quite some time, and the carbonation released, the reaction would not work.

Aspartame is also quite important, as shown by the Diet sodas. There is a claim that only Diet Coke works the best; well we showed that Diet Dr. Pepper is just as good. The next time I get ambitious enough to experiment with this, I think I'll compare the same regular sodas with their diet counterparts.

Science Sundays

So one day after dinner we had some empty soda cans lying around, and instead of just throwing them away, I decided to dazzle my girls with my Science geekiness. I did the classic soda can implosion trick on the stove, and they loved it. I loved doing it too. After that I really wanted to do more science experiments for my kids, to create a spark that will hopefully keep them interested in science for the rest of their lives. I did the soda can trick a few more times, and they still love it. After doing them sporadically a few times, I decided we needed some structure. We're usually too busy during the week to have a structure of this sort, so I thought Sunday afternoon might be good. With that 'Science Sundays' was created. As of right now, the plan is to do a science experiment on the 1st and 3rd Sundays of the month. Some will be public, others will be private and quiet.