Rolling Meadows High School (District 214) is actively looking for a chemistry teacher for the 2002-2003 school year. Responsibilities will include 1 AP Chemistry Class and 3 additional classes of chemistry or physical science. Rolling Meadows has an eight-block AB schedule. Classes meet for 90 minutes every other day, except for AP Chemistry, which meets every day for 90 minutes. Interested parties should contact Susan Illingworth at (847) 718-5724.
Karlene Joseph (Lane Tech HS): Eggs and Diffusion
Karlene put some raw eggs in a container and covered them with vinegar (H+) for about 4 days. The shells (Ca CO3) dissolved, and we were left with "rubbery eggs"; ie, the raw egg surfaces were covered by remaining membranes. At first Karlene had observed bubbles, as a result of the chemical reactions
Ca CO3 + 2H+ ® Ca++ + H2CO3
H2 CO3 ® H2O + CO2
She weighed a "de-shelled" egg and found that its mass to be 85 grams. Then she placed it in a sugar solution (Karo® Syrup). After about 40 minutes we poured off the syrup, rinsed off the excess syrup, and weighed the egg again, obtaining a mass of 77 grams. Although the membranes on the egg were still intact, water had diffused out through the surface membrane, leaving the egg and mixing into the syrup, which had become more fluid. [The syrup had lower osmotic pressure (for the solute, water) than the egg, providing an osmotic pressure gradient, so that water would undergo diffusion, crossing through the semi-permeable membrane out of the egg and into the syrup.] An excellent exercise illustrating the effect of osmosis, Karlene!
Pat Riley (Lincoln Park HS, Chemistry): Kitchen Chemistry &
Pat divided us into three groups, and each group got one of three liquids:
I: water; II: vinegar; III: dilute solution of KI (potassium iodide) in water
The groups got the following four solids in separate bottles:
Each group also received five unknown mixtures of the solids A - D, which were labeled as 1, 2, 3, 4, 5. Three of them were mixtures of 2 unknown solids, and two were mixtures of 3 unknown solids. We observed which solids dissolved in each of the three liquids, looking first at the "known solids" A - D, and then at the "unknown" mixtures. We determined whether, and to what extent, the visual observations of the "pure substances" would permit determination of "ingredients present in mixtures" for each case 1-5. Little sticks were used as spatulas; samples of solids about the size of a grain of rice were taken for each test. Pat supplied 96-well plastic plates for each test, which greatly simplified the process.
We presented the findings in the following data sheet:
Pat did two more short activities:
Data and Observations
|Substance||Did it Melt?||Did it dissolve
|Did the solution
We had a really excellent session for our last meeting of the year. See you next year!
Notes taken by Ben Stark