TOPS of Santa Clara Valley
Teaching Opportunities for Partners in Science
Decomposition is demonstrated by the electrolysis of water using the Hoffman Apparatus. Over about 30 minutes, students observe that the volume of hydrogen produced at the cathode is twice the volume of oxygen formed at the anode.
Pasta car photo courtesy of Seghei Pakhomoff (firstname.lastname@example.org)
The main role of TOPS volunteers is to work with student groups doing hands-on experiments. Volunteers and teachers also work together to devise techniques to demonstrate fundamental scientific principles in ways that can truly impress the class. Some examples are described below. Click on "Laboratory Procedures" and/or "A-V Presentations" above to see how you can obtain access to files with these experiments and demonstrations.
After showing a PowerPoint presentation on how the elements are thought to be formed in the universe, solutions containing salts of such elements as sodium, copper, lithium and strontium are burned in a flame to show the different colors emitted by each element and how astronomers use these to identify elements in stars.
A short straw is placed into a glass of water and the volunteer blows across the top of the straw with another straw to create an aspirator.
Another demonstration of decomposition involves the addition of concentrated sulfuric acid catalyst to white sugar resulting in the formation of a black carbon foam column, showing how a molecule decomposes.
Chemical Reaction - Synthesis
Shown at the top of this page, this demonstration enables students to observe a synthesis type reaction involving burning of the element magnesium with oxygen in the air to produce a new substance, magnesium oxide.
Students design and build gravity-fed shallow stream beds using fine sand to demonstrate earth movement resulting from water flow. The students design stream flow paths and mark the locations of target inside and outside current flows with numbered flags. When water is allowed to flow, the students observe the volume and distance the earth is moved as well as how earth is moved downstream and banks are undercut .
A balloon is rubbed across one student’s hair and it stands on end. The balloon is then held against the white board where it stays.
A simple electrical circuit apparatus is used to pass an alternating electrical current through hot dogs held at their ends by nails, which act as electrodes. The resistance of the hot dog enables it to heat up and cook. This helps students understand Ohm’s Law and relationships between power and current.
“Glue ball chemistry” involves simply adding a saturated solution of borax (sodium tetraborate) to a small quantity of Elmer's glue in a paper cup. The borate ions create cross-links between the polymer chains, making the resulting material more rigid. As the glue is stirred it becomes a rubber ball, which the students can then bounce on the floor.
Velocity and Acceleration
Students build small cars completely out of dried pasta and white glue. They race them down a one meter ramp angled at 30 degrees to see how far they travel over a measured time period. The students can then calculate the velocity and acceleration of their car.
Students measure the change in temperature of water in a small cup from the burning of a small amount of cheese. They then calculate the degrees C rise per unit volume of water and relate food calories to energy in kilocalories.
Newton's Laws of Motion
Using a set of dowel pins, a small wooden cart with a rubber band and three blocks of wood, each with a different mass, students see Newton's Third Law of Motion in action. Students measure the distance traveled by the "Newton" cart when each of the three wooden blocks is released in the opposite direction. They then create a graph to show the relationship between force and mass.
In another experiment, a ping pong ball is kept floating in a stream of air from a hand-held dryer.
The clues to a chemical change are demonstrated by adding colorless hydrogen peroxide to an orange solution of potassium dichromate. Students observe the rapid formation of a new black substance, the formation of a gas, and an increase in temperature as well as how multiple reactions can proceed at different rates - over a period of hours the black mixture finally becomes the final product, yellow potassium chromate.
Many thanks to Mrs. Hope Oliver, Science Department Head, Bret Harte Middle School, San Jose, California, for providing many of the experiments described above.
EXPERIMENTS & DEMONSTRATIONS