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C Jansen's picture

Modified for Test Tubes in a Large Beaker Bath

When I ran this lab 3/12 I decided it made the most sense for me to have each group of 4 use a hot plate with a 1000 mL beaker filled with the warm water for their source of water and for the bath and test tubes (50 mL) for the "cups."

This worked well for a number of reasons:
1. The original directions weren't clear on how big the "cup" should be so that the bubbles don't run over.
2. I have a lot of test tubes, so it worked well to have a lot to pass out.
3. The test tubes can be placed in the large beaker without falling over and up to and passed the liquid line will be fully submerged in the warm water, giving a consistent temp.
4. The hot plates provide a way to keep the water temp where you want it for the whole class period and for the next periods as well.

In order for this switch, to test tubes, to work I needed to cut the amounts of water, yeast, and sugar. I switched to 20 mL water, 1.0 g Yeast, and 0.2 g sugar. This seemed to work very well. The 20 mL of water filled up the tests tubes a little less than half way, providing enough room for the yeast to bubble if it is going to.

I also had my group use plastic weigh dishes instead of paper because they are reusable and I don't have much paper in my room.

Thanks for this lab! I'll be trying out the second part, the baker's challenge next.

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