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August 28, 2007

Quick, give me an experiment for the kid

In order to avoid the now famous South Carolina Catastrophe of 2007 (not exactly what you think), I'm stepping up the experimentation with our girl. Tonight's experiment performed during dinner preparation brought to you by SciFun.org is Dancing Raisins.

Using a clear carbonated drink or the alternative mentioned below:
Drop 6 or 7 raisins into the glass. Watch the raisins for a few seconds. Describe what is happening to the raisins. Do they sink or float? Keep watching; what happens in the next several minutes?

Raisins are denser than the liquid in the soda, so initially they sink to the bottom of the glass. The carbonated soft drink releases carbon dioxide bubbles. When these bubbles stick to the rough surface of a raisin, the raisin is lifted because of the increase in buoyancy. When the raisin reaches the surface, the bubbles pop, and the carbon dioxide gas escapes into the air. This causes the raisin to lose buoyancy and sink. This rising and sinking of the raisins continues until most of the carbon dioxide has escaped, and the soda goes flat. Furthermore, with time the raisin gets soggy and becomes too heavy to rise to the surface.

Another way to do this experiment is to generate the carbon dioxide gas using the reaction of baking soda and vinegar. Fill your glass about 1/2 full empty (I'm a pessimist) with water. Add one teaspoon of baking soda and stir until it is dissolved in the water. Add 6 or 7 raisins to the glass. SLOWLY pour in vinegar until the glass is about 3/4 full. The vinegar and baking soda react to form carbon dioxide bubbles, and the raisins will dance just as in the soft drink!

6 comments:

Big Momma said...

Raising a daughter to be beautiful and smart...what a concept! Cheers to you for planning this experiment. Your daughter will love it.

Dave said...

It wasn't a flashy experiment but kind of fun to watch the little raisins bob up and down. Frankie liked it.

Clam said...

That was so cool, and so cool that she figured out what was carrying the raisins up. I love our kid. We did good, Baby.

Dave said...

Tonight, the collapsing can. I can't wait.

Lorence said...

Boogie and I did this last night, too, but the raisins wouldn't rise more than a 1/2 inch or so, but they were pretty old and sticky.(been in the cupboard for a while)...We're going to try it again with some raisins we've put out in the sun to dry a bit more.

We're going to try the candy chromatography this weekend...

Thanks for the link, Dave!

Dave said...

Hey Lorence,

I had a few troubles with it. Had to use quite a bit of baking soda and had to add vinegar REALLY slowly to get adequate carbonation. As far as the raisins go, it's all in the choice of raisins. We got a really good up and down one the other night using a small raisin that was really wrinkled (so it would adhere to more bubbles). It was still fun redoing the experiment a few times until it worked and thinking just as much about the "failures". I'm thrilled you found it useful.