1. More Atomic History!

2. Matter is discontinuous and there is a smallest particles
Review
Matter is discontinuous and there is a smallest particles
Democritus

3. Nope, matter is continuous, meaning there is no smallest particle.
Review
Nope, matter is continuous, meaning there is no smallest particle.
Everything’s made of earth, wind, fire and water.
Aristotle

4. Review Matter is made of small indivisible particles.
Matter of the same element has the same atoms. Different elements have different atoms.
They combine to form compounds.
Dalton

5. Dalton Models

6. Dalton Timbit Models

7. Neon

8. Neon

9. Anode
(+)
Cathode
(–)

10. Anode
(+)
Cathode
(–)
Cathode ray

11. Fun fact: Old TVs and computer screens (not flat screens) work by cathode ray tubes.

12. J. J. Thomson (1897)
J. J. Thomson was experimenting with cathode ray tubes.
He decided to bring charged electric plates near a cathode ray.

13. Anode
(+)
Cathode
(–)

14. Anode
(+) +
Cathode
(–) –

15. Thomson discovered that the cathode ray appeared to be deflected in the direction of the positively charged plate. Because he knew that opposite charges attract, he concluded that the cathode rays must be negatively charged.

16. Thomson calculated that whatever this negatively charged stuff was, it was much much smaller than the smallest atom. Also, this experiment worked when he tried different metals for the cathode and anode.

19. Atoms are composed of a negatively charged particle
Atoms are composed of a negatively charged particle. This particle is called an electron.
Overall, atoms are neutral. There’s a positively charged shell with embedded negative charges.
Atoms are divisible.

20. Thomson’s atomic model was nicknamed the ”plum pudding model”

22. Remember…

23. Sample Exam Question A is positively charged
So, B is ____________ charged
C is ____________ charged
D is ____________ charged
E is ____________ charged

24. More thoughts on electrons…
In nature, things are electrically neutral. This means it has the same number of positive and negative charges.

25. Rubbing together…
When 2 substances are rubbed together, electrons are transferred from one substance to the other.
Positive charges are NEVER transferred.
When one substance loses electrons, it becomes __________ charged.
When the other substance gains electrons, it becomes _________ charged.

26. When electrons accumulate on the surface of the balloon, do they move around?

28. Charging by friction
2 neutral objects are rubbed together and electrons are transferred from one substance to the other. But which way do the electrons go?
Vinyl Wool

29. Triboelectric series… or how well does something acquire or give up electrons? (p 23 of your workbook.)
Dry human skin
Acetate
Glass
Human hair
Nylon
Wool
Cat fur
Silk
Paper
Cotton
Amber
Ebonite
Rubber
Vinyl
Teflon

30. Triboelectric series… or how well does something acquire or give up electrons? (p 23 of your workbook.)
Dry human skin
Acetate
Glass
Human hair
Nylon
Wool
Cat fur
Silk
Paper
Cotton
Amber
Ebonite
Rubber
Vinyl
Teflon
Tends to give up electrons (becoming positive)
Tends to acquire electrons (becoming negative)

31. Triboelectric series… or how well does something acquire or give up electrons? (p 23 of your workbook.)
Dry human skin
Acetate
Glass
Human hair
Nylon
Wool
Cat fur
Silk
Paper
Cotton
Amber
Ebonite
Rubber
Vinyl
Teflon + -

32. Triboelectric series… or how well does something acquire or give up electrons? (p 23 of your workbook.)
Dry human skin
Acetate
Glass
Human hair
Nylon
Wool
Cat fur
Silk
Paper
Cotton
Amber
Ebonite
Rubber
Vinyl
Teflon + -
Glass Silk

33. What if you bring the same cloth next to silk? What happens?

34. Complete workbook pages on static electricity pages 19-24

35. 3 methods for acquiring electric charge
By Friction:
Rubbing two neutral objects together. One object becomes positive and the other becomes negative.

36. 3 methods for acquiring electric charge
2. By Conduction: You can charge an object by putting a charged object in contact with a neutral object. The result is two objects that have the same charge.

37. 3 methods for acquiring electric charge
3. By induction
This is charging without direct contact. A charged object approaches a neutral object. The charged object remains charged, while the neutral object rearranges its charges to form positive and negative sides

38. Review of charging…
Method Contact? What you start with What you get By friction By conduction By induction

39. Review of charging…
Method Contact? What you start with What you get By friction Yes Two neutrals are rubbed Opposite charges + -

40. Review of charging… + - - - -
Method Contact? What you start with What you get By friction Yes Two neutrals are rubbed Opposite charges By conduction Yes Charged contacts neutral Distributes its charges (like charges) + - - - -

41. Review of charging… + - - - - - -
Method Contact? What you start with What you get By friction Yes Two neutrals are rubbed Opposite charges By conduction Yes Charged contacts neutral Distributes its charges (like charges) By induction No Charged object brought Neutral’s charges near neutral object are redistributed + - - - - - -