Thursday, June 11, 2009

Physics: Whatever floats your boat

This week the kids were given 6 items to analyze. First I asked them to order them by weight. The twist was they had to do it first by guessing, and then by measuring the weights with a scale. The kids were pretty surprised by how wrong their guesses were. We wondered why it was that some things, like say, a large piece of styrofoam "feel" lighter than others when they actually weigh more. We got some clues when we moved on to part two of the lab: testing each item to see if it floats or sinks in water. Wouldn't you know it, the things the kids thought were light, were floaters, and the things they thought were heavy, were sinkers. However, contrary to our expectations, whether something sinks is NOT simply about weight.

Then each kid was given a lump of clay. After observing that it too was a sinker, they were challenged to build a boat out of said sinking clay, and not just that, but a boat that could carry cargo (any number of marbles, also sinkers). After some trial and error, the kids figured out which shapes worked best.

Then, just for fun, the kids made bouncy balls out of water balloons.

General Science: What's a yeast's favorite food?

This week we learned a little bit about our tiny unicellular fungal friend, the yeast. After all, we have a lot in common: We eat, reproduce, respire...we're practically identical. So when it came to investigating which foods yeast like best, we decided to use something else we have in common: When we're done eating (and transforming the energy from food into energy our cells can use), we all release carbon dioxide. This comes in handy when we use yeast to help us make bread. It is the carbon dioxide gas that causes the bread to rise.

We compared carbon dioxide production in yeast when fed 5 different kinds of food: salt, flour, sugar, ground-up cookies, and ground up vaflim (wafers). To get an idea of which food was eaten most heartily by our yeast, we covered each bottle with a balloon. Then we sat back and watched the show. The samples of yeast fed sugar, cookies, and vaflim were the happiest, i.e. the balloons were the most inflated because of the greater production of carbon dioxide. The flour came in second place. We discussed how cookies contain sugar, and how flour, a complex sugar, can be broken down into simpler sugars. A little more work, but when you're hungry, you do what you have to. Yet one more thing we and yeast have in common...LAZINESS! Who here isn't counting down the days 'till summer vacation?!