Chapter 2 Lecture Enrichment Ideas
Have students examine the periodic table and locate the elements that are common in living organisms. Have them determine how many electrons are in the outer shell by looking at the atomic numbers.
Describe how carbon14 breaks down into nitrogen14 and what the differences in protons and neutrons would be between these elements. Explain why some isotopes are radioactive and others are not.
Discuss the formation of ions and how electrons are lost or gained in such formation. Make sure students understand that an ion can be a combination of atoms, and that even large molecules may become ionized at different locations within the molecule.
Consider the protons and electrons of an atom as similar to the ends of a bar magnet, with positive and negative charges attracting each other, and electrons at greater distances from the nucleus having more energy because they are not as closely attracted to the positive charges of the protons.
Adhesion, cohesion and surface tension are difficult concepts for some students. The ability of a water strider to support itself on the water's surface can be described based on water molecules pushing in all directions; lack of water above the surface provides an upward surface tension "support." Water droplets rolling across the hood of a newly waxed car illustrate cohesion, and supporting a water droplet between your fingers viewing with an overhead projector can illustrate both adhesion (to fingers) and cohesion (of water).
Describe how the pH system is logarithmic and how each higher unit is a ten-fold increase in hydrogen ions; since many students lack direct experience with logarithms beyond the "log key" of a calculator, you may want to utilize a projection slide rule to illustrate this scale.
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