On Thursday we had our first "Lab Day". Most days I lecture for a total of about 3 hours - then we need a break. This week's lab was on osmosis and diffusion. Sometimes we use deshelled eggs as cells, other times we use a special tubing called dialysis tubing. The eggs had been soaking in vinegar to a day and a half, but the shells were still intact, so we had a lesson on pH and acidity - the acidity of the vinegar had been exhausted by the CaCO3 in the egg shells. Anyway, I brought some dialysis tubing. This is like sausage skin - so to make a cell, you have to tie each end. Now - what about string? String is something they don't commonly use here, so we unraveled some jute twine. Students placed some water or sugar-water in the cells, then we placed the cells in a pot of either water or a sugar solution. The cells will then gain weight or lose weight depending on which solution they are bathed in. I have never had a class so involved! They completely invested themselves in this very simple demonstration - and the results were very good.
After we finished the osmosis exercise, it was time to look at cells in the microscope. I brought a variety of prepared slides - onion root tip, amoeba, bread mold - the standards for this lab. There are about 10 microscopes available for 33 students. All of the scopes use 110v lights - but Kenyan electricity is 240v. We have a transformer with 2 outlets - how do we get all scopes working. Fortunately, someone had brought several extension cords - each cord ran two scopes with an outlet for the next extension cord, etc. So we daisy-chained the scopes - and it worked! I have never seen a class so excited about looking through the scopes. Not only that, but they stayed after class so they could take pictures of one another looking through the scopes. That in an of itself is a reward after dealing with students in the US who can't wait to leave class - even if they haven't done half the exercise.
More on the students and people of Kenya in later posts - byefornow - HDG
No comments:
Post a Comment