Do Now – September (prime number between 20 and 28), 2009

Please answer the following questions in

COMPLETE SENTENCES.

1. Write a sentence describing what a theory is.

2. Why weren’t cell phones invented when regular phones were?

Agenda

• Do Now/Announcements

• Unit 2 Test Results and Personal Tracking

• Review Theories

• Read article and finish Friday’s notes

• Evolution of Atomic Theory #1

• Work Time (?)

• Exit Ticket

Unit 2 Test Results – 2nd Period

• 100% or above– Chris Treadway

• 90% and above– Raul Baca– Diquan Forcell– Dalvin Hickerson– Ronald Jackson– Omar Martinez– Blake Percle– Alexandria Sierra– Brandon Toney

CLASS AVERAGES

2nd: 85

3rd: 85

Unit 2 Test Results – 3rd Period

• 100% or above– Isaac Wallis

• 90% and above– Patrick Beckham– Jasmine Castro– Jonathan Cordero– Christina DeArmas– Kaynetra Hunter– Angelle Johnson– De’Shawn Lemieux– Jontrel Mackey– Laronda Severance– Cachi Tran– Steven Webb

CLASS AVERAGES

2nd: 85

3rd: 85

Unit 2 Test Results – 4th Period

• 95% or above

• Other As and Bs– Carolyn Dhanraj– Robin Foucha– Briana Petes– Carlos Turner

CLASS AVERAGES

2nd: 78

3rd: 76

4th: 71

Objectives

• SWBAT describe and discuss how theories change over time.

• SWBAT describe the evolution of the atomic theory from 420 B.C. to 1898.

• SWBAT defend a conclusion using research as evidence.

Review• A theory is an explanation

that has been supported by many, many experiments– Supported over time– Subject to new experimental

data and can be modified– Used to make predictions that

are true

How is a THEORY different from a HYPOTHESIS?

• A theory is an explanation that has been supported by many, many experiments– Experiments have already been

conducted to support a theory• A hypothesis is a tentative

explanation for observations that have already been made– Experiments must be conducted

to test hypothesis

CONCLUSIONS

• A conclusion is a judgment based on information obtained in an experiment– Scientists apply DATA to

HYPOTHESIS to form CONCLUSION

Remember!• A hypothesis is a tentative

explanation for observations that have already been made

• A conclusion is a judgment based on information obtained in an experiment

• A theory is an explanation that has been supported by many, many experiments (related to a scientific law)

So what is a SCIENTIFIC LAW?

•A scientific law is a description of nature supported by many experiments–It is a simple description –A theory describes how the law works

–Theories and laws are similar

What is an ATOM?

An atom is the smallest part of an element that retains (keeps) the properties of the element

Remember! Particles hold the identity of matter!

What is an ELEMENT?

An element is a pure substance that cannot be broken down into simpler substances by physical or

chemical means

So How’d They Do It?

How do you think scientists learned about the particles of a substance

when they couldn’t even see them?

In other words, how did they know that all matter was made of tiny

particles?

Unit 3Chemistry Secrets:

Atoms and the Periodic TableWhat should we understand?

History and science are intertwined. We can look back on history and see just how the atom and

periodic table were developed. Theatom is so central to our understanding ofchemistry because it is these particles that

determine what we can observe about all matter. Everything is composed of atoms. Some of our

most pressing international debates today revolve around the structure and properties of the atom.

We have to be informed of ALL models of the atom.

Essential Questions

1) Who made the most important contribution to the development of atomic theory?

2) What makes one atom different from another? How are they similar?

3) Why is it so important to understand how the periodic table is organized?

4) What secrets can we uncover about the elements using the periodic table?

How in the World

Did They Figure All this Out!?!

Big Players in Atomic Theory

Democritus (460-370 B.C.)Aristotle (384-322 B.C.)

John Dalton (1808)J.J. Thomson (1898)R.A. Millikan (1909)

Ernest Rutherford (1909)Niels Bohr (1913)Chadwick (1932)

Numero Uno! - Democritus(460-370 B.C.)

• Experiment: Observations and Inferences (no REAL experiment…just IDEAS)

• Where: Greece

• When: 420 B.C.

• First theory of the atom– The “birth” of the atom

Democritus - Conclusions

•Matter is composed of tiny particles

Named them atomos (Greek)

•Different kinds of particles have different sizes and shapes

•Particles move through empty space

Page 88

Number 2 - Aristotle(384-322 B.C.)

• Aristotle gave us this quote…– “We are what we repeatedly do.

Excellence, therefore, is not an act but a habit.”

• Among other things…– He challenged the ideas of

Democritus– He did not think the

“nothingness” of empty space could exist

Page 88-89

Coming in Third…John Dalton (1766-

1844)

•Experiment: Careful chemical measurements•Where: England•When: 1803

Page 90

Four Postulates• All matter is made of tiny particles called atoms.

• All atoms of a given element are identical, but they differ from those of any other element.

Four Postulates• Compounds are formed by a combination of 2 or more types of atoms.

• Chemical reactions occur when atoms are rearranged.

John Dalton’s Conclusions

•Dalton thought that atoms were hard, round, solid balls (like marbles)

Cuatro! J. J. Thomson (1856-1940)

•Experiment: Cathode ray tube

•When: 1898

•Where: England

•He said the atom was a ball of positive charge with electrons evenly spaced in the atom

•Atoms can be divided into smaller SUBATOMIC particles!

+E

E

E

E

CONCLUSIONS

Compare and Contrast

What are the similarities and differences between each

contribution?

How did each theorist add to or reject the discoveries or ideas developed

before him?

RAFT - Independent Work TimeR = Role

Pretend to be either Dalton or Thomson.A = Audience

You are writing to inform everyone of your discoveries!

F = FormatLetter, Newspaper column, or Rap

T = TopicDetails of your discovery and how you know it is

true - YOU HAVE “WORKED” HARD…DEFEND YOUR RESEARCH!

You may use a chemistry book to help.

Exit Ticket

1. Can people think that theories are correct even when they are not? How does this happen? How is it that theories change?

2. What was Dalton’s biggest contribution to atomic theory?

3. If you achieved the class average on your test, what did you do to get that grade and how will you continue in the future? If you did not get the class average on your test what will you do differently next time to make sure that you do better?

Cinco! R. A. Millikan

• Experiment: Millikan Oil Drop Experiment

• When: 1909

• Where: U.S.A!!!!

Conclusion:Electrons have negative charges!!!

Number Six! Ernest Rutherford

• Experiment: Gold Foil Experiment

• When: 1910• Where: Montreal

Ernest Rutherford

• Conclusions:• Discovered and

named the nucleus• Protons and mass

concentrated at center of atom

• Performed the alpha-scattering gold foil experiment

http://micro.magnet.fsu.edu/electromag/java/rutherford/

More History

Ernie’s (Rutherford) Big AdventureErnie’s (Rutherford) Big Adventure

Thin Sheet of GoldAtoms

++

++

-

-

- -

-

-

- -++

+ +

Rutherford’s Conclusion

• Atoms are made of mostly EMPTY SPACE!– Actually, the ratio of the

size of the nucleus to the diameter of the orbits of electrons can be compared with placing a marble in the middle of a football stadium!

Empty Space Continued

• “Neutrons and protons occupy the atom's nucleus. The nucleus of an atom is tiny -- only one-millionth of a billionth of the full volume of the atom -- but fantastically dense, since it contains virtually all the atom's mass. As Cropper has put it, if an atom were expanded to the size of a cathedral, the nucleus would be only about the size of a fly -- but a fly many times heavier than the cathedral.” -A Short History of Nearly Everything by Bill Bryson

Assignment: RAFT

• Option 1: Rap

• Role: An atomic Theorist

• Audience: Writing to another atomic theorist

• Form: an appropriate rap

• Topic: Why your theory and model is better than theirs

+3 points for presenting on Monday

Assignment: RAFT

• Option 2: Polite, Formal Letter

• Role: An atomic Theorist

• Audience: Writing to another atomic theorist

• Form: a formal letter

• Topic: Politely stating why your theory and model proves theirs wrong

+3 points for presenting on Monday

Assignment: RAFTThings to Include

• Personal information about both theorists - where they’re from, physical appearance, etc.

• All necessary facts about both theories or models

• How the theory is better than the one that came before it

I’d like you to meet my friend, and your newest friend in Chemistry…The Periodic Table of Elements

On the periodic table there are letters that symbolize the elements.• An element is a substance that is made up

of the same type of atom.

• Example: Aluminum. An aluminum can is made up of TONS of atoms. They are all aluminum particles.

Periodic Bingo

• Place a dot on the element as it is called. See if you can get BINGO!!!!

Atomic Number = Defines the atom

• Top Number OR always the smaller number

• Equals the Number of protons in the atom

Which element has the atomic number???

•6•13•35

Which element has the atomic number???

•10•82•47

Atomic Mass = mass of the nucleus

• Bottom Number OR always the bigger number

• Equals the number of protons and neutrons

Which element has an atomic mass of…

•12•27•11

Which element has an atomic mass of…

•56•31•238