Tuesday, March 30, 2010

Bad Chemistry

Even after the following experiment I am still prepared to believe that this is a good book.
Illustrated Guide to Home Chemistry Experiments: All Lab, No Lecture (DIY Science)
It is rare, however, that you run into more trouble by following the directions than you would have by winging it.

I read the first experiment, exploring differential solubility and thought it would be a nice intro to chemistry.  As I remembered the challenge was to mix a measured quantity of salt and sand and then try to separate them.

I hoped the kids would try several ideas before they hit on the idea of putting the whole mixture in water and then pouring it through a filter which would let the salt dissolved in water through, but catch the sand.

But then I had to go and take a second look at the experiment.  It calls for sugar and sand, not salt and sand.  So, okay, we did sugar and sand.

The sand was from our sand box which sat open for a while and collected a lot of...umm...organic matter.  So we used a sieve to get rid of the sticks and dead bugs.

Our scale was not so accurate, so we decided to mix 100 grams of sugar and 100 grams of sand.  If all went well we should get back the amount we put in.

One of the kids figured out that the sugar was soluble and the sand wasn't pretty much instantly and shared the knowledge, so I didn't get to witness any scenes worthy of a fairy tale: oppressed children trying to sort the sand and sugar grain by grain.

Instead they ran right to the sink with their jars.

So after running the sand and water mixture through a filter we ended up with several pots of sugar water and several lumps of wet sand.  The sand went into the oven to dry and the sugar water went onto the stove.  Because hey, we'd just evaporate the water, and there would be the sugar, right?

Yeah, right.  Instead we got pots of burnt caramel.

What's worse is that when I wasn't looking the kids ate the dirty burnt caramel! 
At least it was sterile.
Most of the trays of sand hadn't been rinsed, so instead of getting sand back in most cases we got rock hard sand cookies with the filters stuck to them.

Evelyn wanted to get rid of the filter so it wouldn't add to the weight of the sand.   But she didn't want to lose the sand stuck to the filter.  Here was her solution.
She burned away the filter, leaving the sand and a few ashes.

Did we learn anything from this experiment?  Why sure.  Ideas were generated and tried: dissolving the sugar and burning the filter.

We learned that we should have rinsed the sand with water to make sure we'd gotten all the sugar out of the sand.  We learned that if you want to evaporate water to get sugar back you have to be patient, or you will get a chemical reaction.

And I learned that I need to set guidelines on eating the results of our experiments.


AM said...

I want my Dickensian sugar/sand hand sorting scene. For the next assignment ... how about building a pyramid? Or raising an obelisk?

Karen said...

I love your experiments.

I always feel like I learn something right along with you guys - I am thinking of the gingerbread houses and the clay-dyed shirts in Hawaii here :-) - and the way that you write about your girls' approach to science always seems as if it might also reflect their approach to life.

Great post!

Stefaneener said...

Valuable lessons all. Of course, if it were my kids, they'd get off track remembering fairy tales where animals did the sorting for the person, or worse, decide to dissolve the sugar in their mouths right out of the sand or something equally "educational."

Susan said...

AM, I know, wouldn't the sorting have been great?

Karen, I think you are right...this was a classic In The Kitchen experience for us. It didn't go according to plan but we got hands on and learned a lot.

Stefani, dissolving it in their mouths! Ha! Clever solution to the problem, though it would have been difficult to weigh the results. I suppose with a very accurate scale we could weigh the children before and after.

Kristin said...

What an interesting adventure in the kitchen.

--Sounds like the methodology was the biggest part of this science lesson. I'm wondering what they expected to happen, what they hoped to discover before they began--and what their final conclusion about the whole process was?