Experiment 1: Additional information for teachers
The set-up for this lab is very forgiving. Here is how I set it up:
- About 15 minutes before the lab, I dissolve Karo syrup
in warm water (about one liter for two classes at a time) the concentration
of the solution is about 20% syrup and 80% warm tap water.
- To this I add a teaspoon of baker's yeast. I make up a large volume because I like the results we get when we use the larger size of test tubes about two-thirds full.
- Allow some space for foam. Check out the photos on the web page for this
activity.
- It is important that you don't prepare the solutions for
the whole day at the beginning of your day. The yeast work quickly and
reproduce. Two to four hours later the yeast are forced to slow down
their rate of fermentation either because of food shortage or waste products.
Since the prep is reasonably easy, make the solutions as you progress
through the day.
- As far as wait time, the lab does note that students
should allow 5 minutes wait time between stoppering the tubes in cold
water and inserting the free end of the delivery tube into water
(contraction of air will suck up some of the water).
NOTE: I caution my students about solution spillage. Ants really are drawn to the yeast/glucose mix and I warn my students that the ants will test
their thoroughness at lab cleanup and of course, if these little sugar
indicators are positive, the kids will have to fight off the ants!
|
Teaching & Learning Index
