Tues Feb 8, 2011

Start with a BULA! and Say Something Nice to Your Partner

Collect Parent Notification Forms
Collect Course Expectation Forms

Check for Textbook Covers
Those that have covers don't need to bring their books to class until I request them.
Those without covers by Wednesday will stay after school in my classroom and put on a cover.

Quiz on Expectations
Went over Quiz

Journal:
Table of Contents:
Demo - Magic Jar
Demo - Charged strip and water
Demo - Charged straw on pop bottle
Demo - 2x4 and charged ebonite rod

Content:

Demo - Magic Jar
Description - When you turn it upside down, the plastic stays on
Reason - Air Pressure
Main Ideas: Air is made of matter
The air we breathe is about 20% oxygen O2 and 80% nitrogen N2
At room temperature these exist as 2 atom molecules and are in the gaseous state
All matter is made of atoms, tiny particles

Description - When you remove the plastic, the water stays in
Reason - cohesion and surface tension
Cohesion - water molecules are attracted to each other
That is why they form drops
co - together or same coexist, cohabit, coagulate (blood clots), coalesce (grow together, unite, join)
hesion - stick
Adhesion - water molecules are attracted to some other material

Mensicus in graduated cylinder - example of adhesion, water more strongly attracted to glass
If you did the same with mercury, the meniscus would be the opposite way since cohesion greater than adhesion.

Show picture of cohesion and surface tension. Surface molecules are pulled down. This makes a tight surface that bugs can walk on.

Demo - Stream of water attracted to charged strip or rod
Reason - Electrical nature of matter
Main Idea - Atoms and molecules have electrical properties
Picture of an atom is that it has a central, positively charged nucleus made of positively charged protons and neutrons that have no charge. (Neutron in a bar joke)
Each of these "nucleons" (particles in the nucleus) has about the same mass.
Surrounding this nucleus are the electrons, which have much less mass than the protons or neutrons. These electrons are negatively charged. Most matter is neutral because there are about the same numbers of positive charges (protons) - pro- for positive
as electrons (negative charge)

Water is the "Mickey Mouse" molecule of chemistry. The chemical formula for water is H2O meaning there are two hydrogen atoms and one oxygen atom in each molecule of water. But...the atom has ears, it is not in a straight line. The hydrogen ears are the positive end of the molecule and the oxygen head is the negative end. In the stream of water, the water can rotate so the opposite charge is closer and attracted to the charged strip.

A strip of the opposite charge would also attract the water, the water would just rotate the other way.

Demo - Charged straw on pop bottle
Demo - 2x4 and charged rod
Demo - Balloon "sticks" to wall
Main Idea - Charge polarization and the electrical nature of matter. Even neutral matter can be attracted to charged objects.
The atoms in the wood can't rotate but the electron cloud can shift a bit in the molecules making the opposite charge closer.

Demo - Van de Graaff Generator - hair stands on end
Main Idea - Like charges repel
The extra electrons want to get as far away as possible from each other.

Discharge - provides a path to get even farther away

HW do both Quias
Students who do not do them and get at least 90% will stay after school in my room and work on them