High School Biology-Chemistry SMILE Meeting
23 April 2002
Notes Prepared by Porter Johnson
Ann Parham and Winifred Malvin (Carver Primary School) -- The
Bottle Volcano; The Mysterious Balloon; Density
Ann and Winifred put a bewildering array of plastic bottles, stains, dyes, and such on the front desk so that we could all make a Bottle Volcano! They handed out information obtained from The Know How Book of Experiments by Heather Amery: [EMC Paradigm, September 1978]; ISBN: 088436531X
We filled two identical bottles with hot and cold water, respectively, and then put the bottle holding (colored) hot water on the bottom, and the inverted cold water bottle on top, with a piece of thin cardboard separating them. We carefully removed the cardboard without spilling water, and noticed that the colored hot water (less dense) flowed into the upper bottle to the top. We concluded that the less dense hot water was "floating" on a sea of cold, less dense water. Ann did the experiment with very hot water [obtained from a coffee pot] and quite cold water, and we observed that the Volcano works best when there is a great temperature difference in the two components. We discussed the similarity in this phenomenon and the formation of thunderstorms during warm periods, as warm air at the surface of the earth rises into the region of denser, colder air aloft.
Then Winifred did the Mysterious Balloon demonstration, in which a wooden skewer [shish kabob stick] is pushed through the top of balloon, and then down through the bottom. Winifred noted that the balloon acts like a white blood cell that can engulf a foreign object [skewer] without rupturing. The latex molecules in the balloon apparently form a tight seal around the skewer, analogously to the way in which the fluid membrane of a cell engulfs a foreign object (virus, bacterium, etc) without rupturing.
Then Winifred had us prepare three [100 ml] samples -- one of clear water, one of water with 1 teaspoon (10 g) of dissolved salt, and one of water with 2 teaspoons of dissolved salt. The saline solutions were dyed to make them green and red, respectively. We each took a clear drinking straw and placed it upright by sticking one end in a piece of modeling clay, which also sealed that end. We carefully (slowly!) added about 1 ml aliquots of each solution of the straw with eye droppers in a "random order"; in addition the three solutions were "stacked" in the straw in order of decreasing density; that is, with the most dense at the bottom, etc. The most dense solution contained 2 teaspoons of dissolved salt, and the least dense had no salt at all. The color pattern made it easy to distinguish the three layers. If done with sufficient care, one could make a more dense solution layer lie underneath a less dense layer, if the less dense layer is slowly put in first. Very stimulating, Winifred and Ann.
Barbara Pawela (retired and happily active) -- Spring
Barbara showed her tomato plants that sprouted from seeds 2½ weeks ago -- which are 2 -3 cm tall -- most with just 2 leaves, which are called cotyledons. For further information on nurturing and growing tomato plants, see the Tomatosphere Tips website: http://www.tomatosphere.org.
Barb then put two clear plastic cups [about 250 ml] on the table. One of them was filled with potting soil, and the other was filled with "Schultz Seed Starter", which contains vermiculite [soil conditioner] and other materials. For more details concerning this material, see the Schultz Company website http://www.schultz.com/.
We examined each cup for porosity of material, and added the same fixed volume of water to each one. The potting soil was able to absorb water more readily. The seed starter will keep things a little more dry around germinating seeds, and helps prevent rotting of new seedlings, a problem that is very common in an overly moist environment.
Barb then had us start bean seedlings by placing the beans onto dampened paper towels, which we then sealed in zip-lock bags. We next planted cantaloupe and watermelon seedlings in pots. Now we are ready for Spring to come, thanks to Barbara!
Notes taken by Ben Stark