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Friday, April 15, 2011

Kitchen Chemistry - One Day of Discovery

We kicked off our new theme of Kitchen Chemistry/Food Science in style today! The children are SO excited to really dig deep into the scientific method. Today, we did not one, not two, not three, but FOUR explorations using items found in the kitchen.

The first experiment was called Marshmallow Blow Up. We used four marshmallows per group - one was the control (a term we will return to often), one was microwaved for 10 seconds, one was microwaved for 30 seconds, and one for a full minute. The science behind this? When air inside a closed container is heated, its molecules begin to move more quickly and exert more pressure on the sides of the container. In effect, the hot air tries to expand, and when it is enclosed in a flexible container - such as a marshmallow - it can push against the container enough to make the container expand as well. This experiment is a good demonstration of Charles's Law, which states the the volume - the amount of space something takes up - of a gas increases when its temperature increases.

The next demonstration was called The Naked Egg (the kids loved this). I simply immersed a raw egg in a vinegar bath. We talked about how vinegar is an acid, and the kids already figured that the vinegar would take off the shell. We hypothesized how long it would take - until the end of the day? By Monday? Two weeks? We shall see...

Apples and Oranges is the name of the third experiment. Each group had three apple slices - one to use as the control, one that had a slice of orange placed on it, and a third that was put in a bowl of orange juice. I talked about how browning of food is a common chemical reaction that happens in kitchens around the globe. The science behind this? Every cell in an apple contains a chemical called polyphenol oxidase (PPO). When an apple is sliced, some of its cells are opened. This causes the PPO to be exposed to the air, which forces PPO to undergo a chemical reaction with the oxygen in the air. This process is known as oxidation. Stopping oxidation will stop the browning. In this experiment, we blocked the oxygen by adding ascorbic acid to prevent the chemical reaction from taking place.

And finally, the sweet surprise. We made our own ice cream! This is an excellent demonstration of kitchen chemistry. There are four components to ice cream that come together to give it the correct texture and consistency - the liquid component, solid ice crystals, milk fat, and trapped air bubbles. Combined in the proper proportions, and you've got yourself some great ice cream! We also learned the importance of proper sealing techniques, as some of the kids ended up with rather salty ice cream as the rock salt leaked into their plastic bag - yuck!

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