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1. Electrical Nature of Matter Grade Nine Science
2. Question to Ponder What happens when you rub a balloon against your hair?
Does this action create electric charges?
3. What happens when you rub the balloon against your hair? Both items have negative and positive charges.
In fact, both items are said to be neutral
Since the balloon and your hair are comprised of two different materials one item wants the negative charges more.
One item becomes positive, the other negative
Now each item is said to be charged.
4. Electrostatics: study of static electric charge. Static electricity (When Charges DO NOT Move).
This is why the balloon can stick to the wall
This is a result of ?The Law of Electric Charges?
5. The Law of Electric Charges Like charges repel one another, and unlike charges attract one another.
How would you test for this?
Place a known charge to an object with an unknown charge
6. A Model for the Electrical Nature of Matter The Bohr-Rutherford model helps us understand how matter is structured and how it behaves.
The main ideas of this model are presented on the next couple of slides.
7. A Model for the Electrical Nature of Matter All matter is made up of particles called atoms.
At the centre of each atom is a nucleus, with two kinds of particles: the positively charged proton and the uncharged neutron. Protons do not move from the nucleus when an atom becomes charged.
8. A Model for the Electrical Nature of Matter Negatively charged particles called electrons surrounds the nucleus. When atoms become charged, only the electrons move from atom to atom.
Like charges repel each other; unlike charges attract each other.
Some elements have a weaker attraction for its electrons than others and the electrons are able to move freely from atom to atom. A good example is copper
9. A Model for the Electrical Nature of Matter A single atom is always electrically neutral.
If an atom gains an extra electron, the net charge on the atom is negative and it is called a negative ion. If an atom loses an electron, the net charge on the atom is positive and it is called a positive ion.
10. Negative Ions If an atom gains an extra e-, the net charge on the atom is negative , and it is called a negative ion .
6 protons (6+) 6+
6 electrons (6-) 7-
Neutral 0 (no charge) 1- (-ion)
11. Positive Ions If an atom loses an extra e-, the net charge on the atom is positive , and it is called a positive ion .
6 protons (6+) 6+
6 electrons (6-) 4-
Neutral 0 (no charge) 2+ (+ion)
12. Homework Page 273 ? questions 1-5