Thursday, March 1, 2012

General Science: Chemistry in a bag

This week the kids carried out a really complicated lab. They mixed 4 different materials (calcium chloride, sodium bicarbonate, water, and phenol red) in a plastic bag. The materials that were liquids weren't added directly. Instead we first poured them into plastic cups, which themselves were carefully placed in the bag. Why all the extra steps? This allowed us to measure the mass of the whole business BEFORE and AFTER the chemical reaction took place. The kids were pretty surprised to find very little if any change. That's conservation of mass for ya!

As the materials combined the kids observed and recorded the many chemical changes that took place including: bubbles, color changes, and temperature changes. While all these changes were pretty cool, the fact we had combined so many different things at once made it tough to know what was really going on. Part 2 of the lab was breaking down the initial experiment into every possible combination of ingredients, carrying them out, and analyzing the results. By the end the kids new exactly which combo was responsible for each change.

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