chapter 3 & a li’l bit about “moles” chapter 3 & a li’l bit about “moles” plus...

Chapter 3 & A Li’l Bit Chapter 3 & A Li’l Bit About “Moles”About “Moles”Plus some problem-solving techniques from Chapter 4. We Plus some problem-solving techniques from Chapter 4. We aren’t going to do all of chapter 4, but if YOU are having aren’t going to do all of chapter 4, but if YOU are having difficulty with problems, I would review this chapter in detail difficulty with problems, I would review this chapter in detail on your own.on your own.

Objective A Objective A (remember, the objective refer to the Study (remember, the objective refer to the Study

Guides)Guides)http://www.magazine-agent.com/officials-logic-problems/magazinehttp://www.magazine-agent.com/officials-logic-problems/magazine

Look at the following numbers. How Look at the following numbers. How easy would it be to memorize this list easy would it be to memorize this list and regenerate it in a week or so on a and regenerate it in a week or so on a quiz?quiz?

1, 3, 5, 11, 21, 43, 85, 171, 341, 683, 1, 3, 5, 11, 21, 43, 85, 171, 341, 683, 1365, 2731, 5461, 10923, 218451365, 2731, 5461, 10923, 21845

Pretty hard? Pretty Easy? Why?Pretty hard? Pretty Easy? Why?

Easy huh? OK, what’s the next Easy huh? OK, what’s the next number in the sequence? How number in the sequence? How about the next 5 numbers?about the next 5 numbers?

How bout this?How bout this?http://shop.crackerbarrel.com/online/shopping/default.asphttp://shop.crackerbarrel.com/online/shopping/default.asp

What if I never mentioned the list again? What if I never mentioned the list again? What if at the end of the semester…the day What if at the end of the semester…the day before the SOL…I asked you to remember before the SOL…I asked you to remember those numbers?those numbers?

Could you do that?Could you do that?

If so, you’re going to do really, really well If so, you’re going to do really, really well when I asked you to memorize some when I asked you to memorize some “polyatomic ions” on page 147 of your “polyatomic ions” on page 147 of your textbook.textbook.

My guess is you wouldn’t remember though.My guess is you wouldn’t remember though.

Cracker Barrel “Brain Teaser” Game

Can you make sense Can you make sense out of NONSENSE?out of NONSENSE?

ForceForce HourHour UponUpon NeighNeigh

KoranKoranForceForce CisCis ShunShun

HeavenHeaven FodderFodder CountCount

YeYe BratBrat AnentAnent

SagoSago FarceFarce AnewAnew

No luck?No luck?

The Gettysburg AddressThe Gettysburg Addresshttp://www.old-picture.com/defining-moments/pictures/Abraham-Lincoln-Antietam-Battlefield.jpghttp://www.old-picture.com/defining-moments/pictures/Abraham-Lincoln-Antietam-Battlefield.jpg

http://en.wikipedia.org/wiki/Gettysburg_Addresshttp://en.wikipedia.org/wiki/Gettysburg_Address

““Four score and seven years ago our Four score and seven years ago our fathers brought forth on this continent fathers brought forth on this continent a new nation, conceived in Liberty, and a new nation, conceived in Liberty, and dedicated to the proposition that all dedicated to the proposition that all men are created equal.” men are created equal.”

Abraham Lincoln delivered these words Abraham Lincoln delivered these words on Nov 19, 1863. (Go back a slide and on Nov 19, 1863. (Go back a slide and read down instead of just left to right).read down instead of just left to right).

Being able to look at something new, Being able to look at something new, and make sense of it is an important and make sense of it is an important skill for the rest of this course. skill for the rest of this course.

Yes, Ms Rackley, I know this was Antietam, but it’s a nice picture.

1, 3, 5, 11, 21, 43, 85, 171, 1, 3, 5, 11, 21, 43, 85, 171, 341, 683, 1365, 2731, 5461, 341, 683, 1365, 2731, 5461,

10923, 2184510923, 21845http://www.antiqueradiomuseum.org/RR%20Rule%20Book%20for%20CMSP&P%20RR.jpghttp://www.antiqueradiomuseum.org/RR%20Rule%20Book%20for%20CMSP&P%20RR.jpg

The numbers don’t seem to The numbers don’t seem to follow any kind of pattern.follow any kind of pattern.

But, what if you knew a rule? It But, what if you knew a rule? It wouldn’t just be memorization wouldn’t just be memorization then.then.

OK, good point! The rule is:OK, good point! The rule is: Start with 1.Start with 1. Double and add 1.Double and add 1. Double and subtract 1.Double and subtract 1. And so on.And so on.

You just wish it was that EASY!

Let’s look at the numbers Let’s look at the numbers againagain

http://equintconsulting.com/wp-content/uploads/2008/10/istock_000005164183small.jpghttp://equintconsulting.com/wp-content/uploads/2008/10/istock_000005164183small.jpg

1, 3, 5, 11, 21, 43, 85, 171, 341, 1, 3, 5, 11, 21, 43, 85, 171, 341, 683, 1365, 2731, 5461, 10923, 683, 1365, 2731, 5461, 10923, 2184521845

Start with 1.Start with 1.

Double and add 1. Doubling 1 gives me Double and add 1. Doubling 1 gives me 2 and adding one gives me 3.2 and adding one gives me 3.

Double and subtract 1. Doubling 3 Double and subtract 1. Doubling 3 gives me 6 and subtracting 1 gives me gives me 6 and subtracting 1 gives me 5.5.

Learn HOW to do the problem; Learn HOW to do the problem; don’t just memorize the don’t just memorize the

answer!answer!http://familyfun.go.com/Resources/printable-previews/previews/beaver_memorygame_august2.jpghttp://familyfun.go.com/Resources/printable-previews/previews/beaver_memorygame_august2.jpg

Doesn’t “knowing the rule” make Doesn’t “knowing the rule” make the list easier to memorize?the list easier to memorize?

You don’t have to memorize a You don’t have to memorize a bunch of unrelated numbers. bunch of unrelated numbers.

IF YOU KNOW the rule, you can IF YOU KNOW the rule, you can generate the number list on the generate the number list on the test easily. Anytime! Anywhere!test easily. Anytime! Anywhere!

Don’t

OK, does this relate to OK, does this relate to Chemistry at all?Chemistry at all?

What makes Chemistry hard for most What makes Chemistry hard for most students, is you DON’T know the rule. You students, is you DON’T know the rule. You didn’t read the book. You didn’t look at the didn’t read the book. You didn’t look at the sample problems. sample problems. You don’t know the You don’t know the RULE!RULE!

Every problem looks like it’s a totally brand Every problem looks like it’s a totally brand new problem. But you’re not solving for x new problem. But you’re not solving for x or y. You’re finding the “density” or some or y. You’re finding the “density” or some other REAL PROPERTY of matter.other REAL PROPERTY of matter.

Every problem looks totally unrelated to Every problem looks totally unrelated to anything we’ve done before.anything we’ve done before.

Objective AObjective Ahttp://www.52shows.com/wp-content/uploads/2009/02/huh.jpeghttp://www.52shows.com/wp-content/uploads/2009/02/huh.jpeg

If we can understand the rules, it makes If we can understand the rules, it makes the problems much, much easier. And if the problems much, much easier. And if you figure out how to do one problem, you you figure out how to do one problem, you should be able to figure out other problems should be able to figure out other problems just like it (like on the test).just like it (like on the test).

Let’s start with a simple problem. I’ll give Let’s start with a simple problem. I’ll give you two numbers, and you tell me the you two numbers, and you tell me the answer.answer.

The numbers are 2 and 3.The numbers are 2 and 3.

What’s the answer?What’s the answer?

Objective AObjective Ahttp://www.platformnation.com/wp-content/uploads/2009/06/shrugging.jpghttp://www.platformnation.com/wp-content/uploads/2009/06/shrugging.jpg

What are you supposed to do What are you supposed to do with those numbers?with those numbers?

It’s like that in Chemistry. If It’s like that in Chemistry. If you don’t have a clue, you don’t have a clue, anything you do is potentially anything you do is potentially just as valid as anything else. just as valid as anything else.

But usually it’s pretty easy to But usually it’s pretty easy to figure out what to do.figure out what to do.

What?

Objective AObjective Ahttp://www.tvgasm.com/newsgasm/Bill-nye.jpghttp://www.tvgasm.com/newsgasm/Bill-nye.jpg

In Chemistry, when we have In Chemistry, when we have numbers, much of the time we numbers, much of the time we do one of three things:do one of three things:

Multiple 2 x 3Multiple 2 x 3 Divide 2 / 3Divide 2 / 3 Divide 3 / 2Divide 3 / 2

If you can figure out which If you can figure out which operation to do when, you can operation to do when, you can actually solve the problem. actually solve the problem. That’s our goal. That’s our goal.

What would Bill Nye do?

Bill Nye is the Guy!

Objective AObjective Ahttp://francisanderson.files.wordpress.com/2009/01/billy-mays.jpghttp://francisanderson.files.wordpress.com/2009/01/billy-mays.jpg

We don’t use abstract or We don’t use abstract or imaginary or hypothetical imaginary or hypothetical quantities in chemistry.quantities in chemistry.

We use real amounts WITH We use real amounts WITH UNITS.UNITS. 5 grams5 grams 14.7 milliliters14.7 milliliters 3.6 x 103.6 x 10-3-3

moles (don’t worry about moles (don’t worry about moles for a while…we’ll get to these)moles for a while…we’ll get to these)

6.02 x 106.02 x 102323 molecules molecules

But wait!There’s more!

Objective AObjective Ahttp://www.vintagecalculators.com/html/texas_insturments_ti_58.htmlhttp://www.vintagecalculators.com/html/texas_insturments_ti_58.html

Notice on the last slide, most of the the Notice on the last slide, most of the the numbers aren’t as nice as 2 or 3.numbers aren’t as nice as 2 or 3.

But so what. You have a calculator. But so what. You have a calculator. Calculators don’t care how hairy the Calculators don’t care how hairy the numbers are…they just add ‘em up.numbers are…they just add ‘em up.

You need to get in the habit of always You need to get in the habit of always using units. If the units in your answer using units. If the units in your answer don’t work out right, the problem is don’t work out right, the problem is WRONG. Try again.WRONG. Try again.

Note the cool red LED numbers

Second calculator I ever got (1977). I got my first one in 1975 and all it did was add, subtract, multiply, divide AND do square roots. Quite an upgrade!

Units TELL you the right Units TELL you the right ANSWER!ANSWER!

If your units don’t work out right, If your units don’t work out right, your answer is wrong.your answer is wrong.

Do the problem over. Read the Do the problem over. Read the problem carefully before you start, problem carefully before you start, and check your work when you get and check your work when you get done. done.

Don’t just ignore wrong units. It is Don’t just ignore wrong units. It is a big clue for you. This is very a big clue for you. This is very important.important.

LISTEN to the units!LISTEN to the units!

Qualitative and Qualitative and Quantitative DataQuantitative Data

Qualitative (think quality)Qualitative (think quality) This is more a description. These are observations This is more a description. These are observations

usually.usually. It’s blue. It’s hot. It’s cool. It’s smells like rotten eggs.It’s blue. It’s hot. It’s cool. It’s smells like rotten eggs. Remember to look for qualitative date when you do your Remember to look for qualitative date when you do your

lab experiments.lab experiments.

Quantitative (think quantity or amount)Quantitative (think quantity or amount) This is telling me how MUCH of something you have.This is telling me how MUCH of something you have. 5.0 g of baking soda. 2L of diet Coke. 4.5 moles of CO5.0 g of baking soda. 2L of diet Coke. 4.5 moles of CO22..

Remember to record quantitative data in your lab Remember to record quantitative data in your lab notebook when you do experiments too.notebook when you do experiments too.

Objective BObjective B

Scientific notation is used to express very large Scientific notation is used to express very large and very small numbers.and very small numbers.

Two very important numbers in chemistry areTwo very important numbers in chemistry are

6.02 x 106.02 x 102323 = 602,000,000,000,000,000,000,000 (Avogadro’s = 602,000,000,000,000,000,000,000 (Avogadro’s Number)Number)

6.6 x 106.6 x 10-34-34 = 0.00000000000000000000000000000000066 = 0.00000000000000000000000000000000066 (Planck’s Constant)(Planck’s Constant)

One is a VERY LARGE number. One is a One is a VERY LARGE number. One is a very smallvery small number. number.

Math Alert!

Objective BObjective Bhttp://phoenix.fanster.com/suns/files/2009/05/pile-of-money.pnghttp://phoenix.fanster.com/suns/files/2009/05/pile-of-money.png

6.02 x 106.02 x 1023 23 is very large. is very large.

Let’s say you had that Let’s say you had that much money. much money.

$602,000,000,000,000,000,000,00$602,000,000,000,000,000,000,000.000.00

If you spent a billion dollars If you spent a billion dollars every second of every day, every second of every day, how long do you think the how long do you think the money would last?money would last?

Objective BObjective Bhttp://musikality.net/wp-content/uploads/2009/02/shocked.jpghttp://musikality.net/wp-content/uploads/2009/02/shocked.jpg

http://hebrewandgreekreader.files.wordpress.com/2009/05/waynes_world_15b15d.jpghttp://hebrewandgreekreader.files.wordpress.com/2009/05/waynes_world_15b15d.jpg

Answer:Answer:

More than More than 19 million 19 million years!years!

Way! No Way!

Power Point AssignmentPower Point Assignment

Another one for everyone…we are going to Another one for everyone…we are going to study “moles” in Chap 7. However, I want study “moles” in Chap 7. However, I want to introduce moles much earlier than that, to introduce moles much earlier than that, and Chap 3 seems like a great time to do so.and Chap 3 seems like a great time to do so.

Research moles online and write a 150 word Research moles online and write a 150 word summary about moles. (Note: mole is a summary about moles. (Note: mole is a chemical UNIT and not a little creature that chemical UNIT and not a little creature that burrows into the ground.)burrows into the ground.)

Be prepared for a one question quiz on Chap Be prepared for a one question quiz on Chap 3!3!

Scientific NotationScientific Notation(we now resume our regularly scheduled power point…)(we now resume our regularly scheduled power point…)

We use scientific notation to more easily We use scientific notation to more easily represent very large and/or very small represent very large and/or very small numbers.numbers.

We represent numbers as a “factor” times a We represent numbers as a “factor” times a power of 10.power of 10.

Let’s look at 500, as an example.Let’s look at 500, as an example.

Scientific NotationScientific Notation

500 = 5 x 10 x 10, right?500 = 5 x 10 x 10, right?

But 10 x 10 = 100 and as you know, 100 = 1 But 10 x 10 = 100 and as you know, 100 = 1 x 10x 1022..

So we can rewrite 500 as 5 x (1 x 10So we can rewrite 500 as 5 x (1 x 1022).).

But 5 x 1 just equals 5, so we usually ignore But 5 x 1 just equals 5, so we usually ignore the “1” and just write 500 as 5 x 10the “1” and just write 500 as 5 x 1022..

That’s scientific notation. I’m sure this is just That’s scientific notation. I’m sure this is just a review for all of you.a review for all of you.


How about 999? The decimal point moves from left How about 999? The decimal point moves from left to right.to right.

999 = 9.99 x 10 x 10999 = 9.99 x 10 x 10

So, 999 = 9.99 x 10So, 999 = 9.99 x 1022..

When you put a large number into scientific notation, When you put a large number into scientific notation, the exponent will be positive.the exponent will be positive.


How about 0.0014?How about 0.0014?

Well, 1.4 divided by 10 = 0.14.Well, 1.4 divided by 10 = 0.14.

0.14 divided by 10 = 0.014.0.14 divided by 10 = 0.014.

0.014 divided by 10 = 0.0014.0.014 divided by 10 = 0.0014.

So we’re dividing by 10 and doing it 3 So we’re dividing by 10 and doing it 3 times.times.


So 0.0014 = 1.4 ÷ 10 ÷ 10÷ 10 So 0.0014 = 1.4 ÷ 10 ÷ 10÷ 10

Or 0.0014 = 1.4 ÷ 10Or 0.0014 = 1.4 ÷ 1033 since we are since we are dividing by 10 three times.dividing by 10 three times.

1.4 = 1.4 x 101.4 = 1.4 x 10-3-3

--------------

101033


So 0.0014 = 1.4 x 10So 0.0014 = 1.4 x 10-3-3. .

The decimal point moved from left to right.The decimal point moved from left to right.

When you put a small number into scientific notation, When you put a small number into scientific notation, the exponent will be negative.the exponent will be negative.

Remember that these are exponents. Negative Remember that these are exponents. Negative exponents don’t mean negative numbers, they mean exponents don’t mean negative numbers, they mean very small numbers (between 0 and 1).very small numbers (between 0 and 1).


101033 = 1,000 = 1,000

101022 = 100 = 100

101011 = 10 = 10

101000 = 1 (NOT 0!!) = 1 (NOT 0!!)

1010-1-1 = 0.1 = 0.1

1010-2-2 = 0.01 = 0.01

1010-3-3 = 0.001 = 0.001

Go up, multiply by 10

Go down, divide by 10

How do we add or subtract How do we add or subtract using scientific notation?using scientific notation? Make the exponents the same, if necessary, and Make the exponents the same, if necessary, and

then just add.then just add.

5.4 x 105.4 x 1033 + 2.6 x 10 + 2.6 x 1022 = ? = ?

Let’s change the second number so that the Let’s change the second number so that the exponents match up…exponents match up…

5.4 x 105.4 x 1033 + 0.26 x 10 + 0.26 x 1033 = 5.66 x 10 = 5.66 x 1033

How do we add or How do we add or subtract using scientific subtract using scientific

notation?notation? Does that make sense?Does that make sense?

Well 5.4 x 10Well 5.4 x 1033 = 5,400 = 5,400 And 2.6 x 10And 2.6 x 1022 = 260 = 260

So 5,400 + 260 = 5,660. Putting that back in So 5,400 + 260 = 5,660. Putting that back in scientific notations gives us 5.66 x 10scientific notations gives us 5.66 x 1033..

Either way, your calculator will do it for you Either way, your calculator will do it for you without any problems.without any problems. Maybe!! Use Maybe!! Use parentheses with scientific notation on TI-83 parentheses with scientific notation on TI-83 and TI-84 graphing calculators or you will get and TI-84 graphing calculators or you will get the wrong answer.the wrong answer.

Math Alert!

How do we multiply or divide How do we multiply or divide using scientific notation?using scientific notation? Even simplerEven simpler

To multiply, you multiply the numbers and add the To multiply, you multiply the numbers and add the exponents.exponents.

4 x 104 x 107 7 × 2 x 10 × 2 x 10-3-3== 8 x 108 x 1044 (80,000)(80,000)

To divide, you divide the numbers and subtract the To divide, you divide the numbers and subtract the exponents. exponents.

4 x 104 x 107 7 ÷ 2 x 10 ÷ 2 x 10-3-3== 2 x 102 x 1010 10

(20,000,000,000)(20,000,000,000)

×

÷

Sample Problems on Sample Problems on Scientific NotationScientific Notation

A 91.43 A 91.43

B 0.000000000154 B 0.000000000154

C 6,378,000 C 6,378,000

D 0.000008D 0.000008

E 149,600,000,000 E 149,600,000,000

F 8934.8F 8934.8

Objective c…Accuracy, Objective c…Accuracy, Precision and ErrorPrecision and Error

http://www.edupics.com/en-coloring-pictures-pages-photo-dartboard-p9574.jpghttp://www.edupics.com/en-coloring-pictures-pages-photo-dartboard-p9574.jpg

Think of a dartboard. You Think of a dartboard. You are trying to hit the are trying to hit the bullseye.bullseye.

Accuracy is hitting what Accuracy is hitting what you are aiming for.you are aiming for.

Precision is hitting the Precision is hitting the same spot over and over.same spot over and over.Is this accurate,

precise, or both, or neither?


http://comps.fotosearch.com/comp/IGS/IGS170/dartboard-darts_~IS028-013.jpghttp://comps.fotosearch.com/comp/IGS/IGS170/dartboard-darts_~IS028-013.jpg

Think of a dartboard. You are Think of a dartboard. You are trying to hit the bullseye.trying to hit the bullseye.

If you hit the edge of the If you hit the edge of the dartboard, you are not dartboard, you are not accurate.accurate.

If your darts are all over the If your darts are all over the place, you are not precise.place, you are not precise.Both

accurate AND precise!

Objective c…Accuracy, Objective c…Accuracy, Precision and ErrorPrecision and Errorhttp://www.durhamtech.edu/graphics/programs/univtransf/chemlab1lg.jpghttp://www.durhamtech.edu/graphics/programs/univtransf/chemlab1lg.jpg

In Chemistry labs, we will take measurements.In Chemistry labs, we will take measurements.

Accuracy is how close you are to the TRUE value.Accuracy is how close you are to the TRUE value.

Precision is how close all of your measurements are to each other.Precision is how close all of your measurements are to each other.

Take your time. Know what you are doing BEFORE you do it.

Pay attention to detail. No one in this group is not involved.

You’ll get good results.

Everyone working together safely and observing what’s happening.


Can you be accurate (or Can you be accurate (or have accuracy) with only 1 have accuracy) with only 1 measurement?measurement?

Can you be precise (or Can you be precise (or have precision) with only 1 have precision) with only 1 measurement?measurement?

Yes, accuracy is compared to a “true” value.

No, precision is “closeness” to all other measurements


Student A had 3 measurements: 80, 85, 90Student A had 3 measurements: 80, 85, 90Average = 85.0Average = 85.0

Student B had 3 measurements: 84.9, 85.0, Student B had 3 measurements: 84.9, 85.0, 85.1 85.1 Average = 85.0Average = 85.0

Student C had 3 measurements: 82.1, 82.2, Student C had 3 measurements: 82.1, 82.2, 82.382.3 Average = 82.2Average = 82.2

Student D had 3 measurements: 70.2, 82.2, Student D had 3 measurements: 70.2, 82.2, 94.294.2 Average = 82.2Average = 82.2

The accepted value = 84.9. Who is The accepted value = 84.9. Who is accurate? Who is precise?accurate? Who is precise?

Accurate, Not Precise

Not Accurate, Not Precise

Accurate, Precise

Not Accurate, Precise

Objective C…ErrorObjective C…Error

I put the formula for error and % error in your I put the formula for error and % error in your study guide.study guide.

The error is the difference between the The error is the difference between the experimental value and the actual or true value. experimental value and the actual or true value. We take the “absolute value” because there’s no We take the “absolute value” because there’s no such thing as “negative error.”such thing as “negative error.”

Being 5% high is the same as being 5% low. Being 5% high is the same as being 5% low. You You still have 5% error in either case.still have 5% error in either case.


If the actual value is 10, it doesn’t matter if If the actual value is 10, it doesn’t matter if you get 9 or you get 11. You are still off by a you get 9 or you get 11. You are still off by a unit of “1”unit of “1”

% error = Error / True Value x 100% error = Error / True Value x 100

Using our example, % error = 1/10 x 100 or Using our example, % error = 1/10 x 100 or 10%.10%.


We will discuss error primarily in our labs. We will discuss error primarily in our labs. Be Be sure to include a discussion of any errors that sure to include a discussion of any errors that happened in your experiment in your happened in your experiment in your “Analysis of Data” section of your lab report.“Analysis of Data” section of your lab report.

What kind of errors can you have in your What kind of errors can you have in your labs?labs? Two kinds:Two kinds:

RandomRandom SystemicSystemic

Objective C…ErrorObjective C…Errorhttp://www.budapesthotels.com/sitepic/error_button.pnghttp://www.budapesthotels.com/sitepic/error_button.png

http://images.intomobile.com/wp-content/uploads/2009/06/easy-button.jpghttp://images.intomobile.com/wp-content/uploads/2009/06/easy-button.jpg

Random errors are mistakes. You Random errors are mistakes. You can take care to reduce or eliminate can take care to reduce or eliminate random errors. random errors. These usually come These usually come from being unprepared (not reading from being unprepared (not reading the lab prior to doing it), rushing to the lab prior to doing it), rushing to get done, and careless errors (like get done, and careless errors (like forgetting to do a step).forgetting to do a step).

Systemic errors are errors that are Systemic errors are errors that are present in your system. You can’t do present in your system. You can’t do anything about these. anything about these. If your data is If your data is precise, but not accurate this might precise, but not accurate this might indicate that you had systemic error.indicate that you had systemic error.

Easy Button

Error Button

Objective d…Significant Objective d…Significant FiguresFigures

http://www.musicdirect.com/shared/images/products/large/aayremyrtle.http://www.musicdirect.com/shared/images/products/large/aayremyrtle.http://becauseican.co.za/wp-content/uploads/2008/04/ruler_0_10.jpghttp://becauseican.co.za/wp-content/uploads/2008/04/ruler_0_10.jpg

http://mrsdlovesscience.com/meniscusirr.jpghttp://mrsdlovesscience.com/meniscusirr.jpg

Measure the block of Measure the block of wood using the ruler. wood using the ruler. How long is it?How long is it?

How much water is in How much water is in the graduated cylinder?the graduated cylinder? 23.0

mL?? mL


When you take measurements in Chemistry class or When you take measurements in Chemistry class or in lab, you have to worry about how many significant in lab, you have to worry about how many significant figures (usually abbreviated as sig figs) you have.figures (usually abbreviated as sig figs) you have.

What are sig figs?What are sig figs? All the digits you can read and the first one you can All the digits you can read and the first one you can

estimate.estimate.

Between 7.1 and 7.2, so record as 7.15. All 3 digits are significant, because you read the first 2 and estimated the last 1.


http://www.freefoto.com/images/2000/98/2000_98_1---Number-Zero_web.jpghttp://www.freefoto.com/images/2000/98/2000_98_1---Number-Zero_web.jpg

However, if you didn’t measure However, if you didn’t measure it, there are rules for figuring it, there are rules for figuring out how many sig figs out how many sig figs something has.something has.

RULE #1. All non-zero digits RULE #1. All non-zero digits are significant.are significant.

So that means that the only So that means that the only thing you have to determine is thing you have to determine is whether or not the zeros are whether or not the zeros are significant.significant.

Significant?

Maybe or maybe not!


Rules are in the study guide.Rules are in the study guide.2. Zeros between non zero digits are 2. Zeros between non zero digits are

significant. So, significant. So, 2.003 has 4 sig figs2.003 has 4 sig figs..3. Zeros at the end of a number AND to the 3. Zeros at the end of a number AND to the

right of the decimal point are significant. So, right of the decimal point are significant. So, 1.000 has 4 sig figs1.000 has 4 sig figs..

4. Zeros at the beginning of a number are 4. Zeros at the beginning of a number are never significant. So, never significant. So, 0.00034 has 2 sig figs0.00034 has 2 sig figs..

5. Exact measurements or exact quantities 5. Exact measurements or exact quantities have an unlimited amount of sig figs. have an unlimited amount of sig figs. Example 1 hour = 60 min. “1” and “60” both Example 1 hour = 60 min. “1” and “60” both have an unlimited number of sig figs.have an unlimited number of sig figs.


Adding/SubtractingAdding/Subtracting Answer cannot have more sig figs AFTER the decimal point Answer cannot have more sig figs AFTER the decimal point

than the number with the lowest number.than the number with the lowest number. Ex: 2.1 + 2.22 + 2.345 = 6.665Ex: 2.1 + 2.22 + 2.345 = 6.665 Answer can only have 1 digit after the decimalAnswer can only have 1 digit after the decimal Correct answer = 6.7Correct answer = 6.7

Multiplying/DividingMultiplying/Dividing Answer cannot have more sig figs than the number with the Answer cannot have more sig figs than the number with the

lowest number of sig figs.lowest number of sig figs. Ex: 2.22 x 2.345 = 5.2059Ex: 2.22 x 2.345 = 5.2059 2.22 has 3 sig figs and 2.345 has 4 sig figs. Answer can only 2.22 has 3 sig figs and 2.345 has 4 sig figs. Answer can only

have 3 sig figs. have 3 sig figs. Correct answer = 5.21Correct answer = 5.21

±1 sig figs off is usually OK. If answer should have 4 sig figs and you have 3, 4 or 5, I won’t mark it wrong.


http://www.tvguide.com/celebrities/stuart-scott/214001http://www.tvguide.com/celebrities/stuart-scott/214001

But isn’t 50 and 50.0 and 50.00 and even 50.000 the exact same number?

Maybe, outside of chemistry class, but not in here.

Let me explain.

50 ≠ 50?

Wha-hap-happen?


50 means that your measurement is somewhere between 49 and 51.

50.0 means that your measurement is somewhere between 49.9 and 50.1



The more sig figs in your measurement, the more confidence you have that it’s “exactly” 50 mL or g.

Objective e…SI Units Objective e…SI Units AKA The Metric SystemAKA The Metric System

http://www.boston.com/ae/celebrity/more_names/blog/KG.JPGhttp://www.boston.com/ae/celebrity/more_names/blog/KG.JPG

You need to know THESE:You need to know THESE:

Meters for length (m and cm and Meters for length (m and cm and nm)nm)

Kilograms for mass (kg and g)Kilograms for mass (kg and g) Kelvin for temperature (K)Kelvin for temperature (K) cmcm33 or liters for volume (L and or liters for volume (L and

mL)mL) Kilopascals for pressure (KPa and Kilopascals for pressure (KPa and

atm)atm)

1.0 KG?

Objective e…SI Units Objective e…SI Units AKA The Metric SystemAKA The Metric System

You need to knowYou need to know Kilo means 1000 times (1 g = 1 kg)Kilo means 1000 times (1 g = 1 kg) Centi means 1/100Centi means 1/100thth (100 cm = 1 m) (100 cm = 1 m) Milli means 1/1000Milli means 1/1000thth (1,000 mm = 1 (1,000 mm = 1

m)m) Micro means 1/1,000,000Micro means 1/1,000,000thth (1000 (1000 μμg g

= 1 mg or 1,000,000 = 1 mg or 1,000,000 μμg = 1 g)g = 1 g) Nano means 1/1,000,000,000Nano means 1/1,000,000,000thth (1 (1

billion nm = 1 m)billion nm = 1 m) ÅÅ = Angstrom means = Angstrom means

1/10,000,000,0001/10,000,000,000thth (10 billion Å = 1 (10 billion Å = 1 m)m)

μ (mu) = micro

Certified SI Genius

Objective f…DensityObjective f…Densityhttp://www.tungsten-spheres.com/density_model.jpghttp://www.tungsten-spheres.com/density_model.jpg

Density = mass / volumeDensity = mass / volume

Usually has units of g / cmUsually has units of g / cm33

Density of water = 1.000 g / cmDensity of water = 1.000 g / cm33

You should memorize this You should memorize this number!number!

Density is the mass in grams of 1 Density is the mass in grams of 1 cubic centimeter of volume.cubic centimeter of volume.

Densely packed

Objective f…DensityObjective f…Densityhttp://www.stevespanglerscience.com/img/cache/bcb9b8db117ee64376aedaf7af3595ca/http://www.stevespanglerscience.com/img/cache/bcb9b8db117ee64376aedaf7af3595ca/

sevenlayer-2-51908.jpgsevenlayer-2-51908.jpg

Higher density layers on the bottom and lower density layers on the top.

Is oil more or less dense than water?

D = m / V

Objective g…Ice FloatsObjective g…Ice Floatshttp://www.dharma.org/ims/images/pi_ice_on_pond.jpghttp://www.dharma.org/ims/images/pi_ice_on_pond.jpg

Why does ice float?Why does ice float?Why is this a good Why is this a good

thing?thing?Ice is actually kind of Ice is actually kind of

strange. Actually strange. Actually water is a very water is a very unique compound. unique compound.

Most substances are Most substances are more dense as a more dense as a solid than they are solid than they are as a liquid. as a liquid.

Ice is an exception.Ice is an exception.

Objective h…Take your Objective h…Take your Temperature!Temperature!

We don’t use Fahrenheit in this We don’t use Fahrenheit in this course.course.

We use Celcius (°C)We use Celcius (°C)

We also use Kelvin.We also use Kelvin. K = °C + 273K = °C + 273 0 K is called “absolute zero.” 0 K is called “absolute zero.”

Absolute zero is the temperature Absolute zero is the temperature at which all molecular motion at which all molecular motion stops.stops.

View outside my little cuz’s high school Chem class in Miami. Probably a balmy 35°C (308K)

Objective h…Take your Objective h…Take your Temperature!Temperature!

http://www.avogadro.co.uk/miscellany/t-and-p/thermometers.gifhttp://www.avogadro.co.uk/miscellany/t-and-p/thermometers.gif

Kelvin temperature was defined Kelvin temperature was defined to be a measure of the kinetic to be a measure of the kinetic energy of the sample of matter.energy of the sample of matter.

A sample of matter at 300K has A sample of matter at 300K has twice as much kinetic energy as twice as much kinetic energy as a sample of matter at 150K. a sample of matter at 150K. Temperature is directly Temperature is directly proportional to kinetic energy.proportional to kinetic energy.

You must remember how to You must remember how to convert from °C to K and vice convert from °C to K and vice versa. It WILL be on the test.versa. It WILL be on the test.

The MoleThe Molehttp://www.naturephoto-cz.com/photos/others/european-mole-22725.jpghttp://www.naturephoto-cz.com/photos/others/european-mole-22725.jpg

http://www.waukeganschools.org/cspchem/stories/storyReader$12http://www.waukeganschools.org/cspchem/stories/storyReader$12

No, not this guy.No, not this guy.

A mole is a “counting unit.”A mole is a “counting unit.”

For example, a dozen is 12 of anything.For example, a dozen is 12 of anything.

A “mole” is 6.02 x 10A “mole” is 6.02 x 102323 of anything. of anything.

1 mole of carbon has 6.02 x 101 mole of carbon has 6.02 x 102323 carbon carbon atoms (or particles) and has a mass of atoms (or particles) and has a mass of 12.0 g (hint, hint: look on the periodic 12.0 g (hint, hint: look on the periodic table and find the mass of C in the top table and find the mass of C in the top left corner).left corner).

The MoleThe MoleSection 7.1, pg 170-181Section 7.1, pg 170-181

we will do Section 2 and 3 in Chapter 7 later.we will do Section 2 and 3 in Chapter 7 later.http://i.ehow.com/images/GlobalPhoto/Articles/2100705/PaperSkyscraperwrittenbyDr.Mom-main_Full.jpghttp://i.ehow.com/images/GlobalPhoto/Articles/2100705/PaperSkyscraperwrittenbyDr.Mom-main_Full.jpg

Suppose I ask you to count this Suppose I ask you to count this stack of paper. I need to know how stack of paper. I need to know how many sheets there are for a class many sheets there are for a class project.project.

You come back in about a minute You come back in about a minute and tell me, “hey, Mr. Schwartz, and tell me, “hey, Mr. Schwartz, there are 1245 pieces of paper there are 1245 pieces of paper there.there.

I don’t believe you could’ve I don’t believe you could’ve counted them that fast, but you counted them that fast, but you assure me the total is correct ± a assure me the total is correct ± a couple of pages either way.couple of pages either way.

How did she do it?

The MoleThe Mole

When I asked for an explanation, the student When I asked for an explanation, the student said, it’s simple.said, it’s simple.

I weighed 1 piece of paper. I recorded that I weighed 1 piece of paper. I recorded that weight and then weighed the entire stack.weight and then weighed the entire stack.

I divided the total weight by the weight of 1 I divided the total weight by the weight of 1 sheet and that gave me 1245.sheet and that gave me 1245.

That’s essentially what we do to count atoms.That’s essentially what we do to count atoms.

The MoleThe Mole

We can’t see atoms. We can’t possibly count We can’t see atoms. We can’t possibly count them, because they are too small.them, because they are too small.

But we know how much 6.02 x 10But we know how much 6.02 x 102323 of them of them should weigh.should weigh.

Let’s say we have 2.12 g of carbon. How Let’s say we have 2.12 g of carbon. How many carbon atoms is that. We know that 1 many carbon atoms is that. We know that 1 mole of carbon has a mass of 12.0 g and 1 mole of carbon has a mass of 12.0 g and 1 mole of C contains 6.02 x 10mole of C contains 6.02 x 102323 atoms. atoms.

2.12 g C = 1.06 x 102.12 g C = 1.06 x 102323 atoms atoms

2.12g C 1 mole 6.02 x 102.12g C 1 mole 6.02 x 102323 atoms atoms

12 g C 1 mole12 g C 1 mole

Real simple: multiply everything on top. Divid everything on bottom. Cancel out units where you can.




Notice that g of C cancels out and mole cancels out, Notice that g of C cancels out and mole cancels out, leaving us with the units of ATOMS for our answer.leaving us with the units of ATOMS for our answer.




We really can’t “count” 1.06 x 10We really can’t “count” 1.06 x 102323 atoms. They are atoms. They are too small. But by doing it this way, we can too small. But by doing it this way, we can calculate how many we have.calculate how many we have.

Mass of an ElementMass of an Element“gram atomic mass” or just atomic mass“gram atomic mass” or just atomic mass

To find the mass of an element, you look it up To find the mass of an element, you look it up on the Periodic Table.on the Periodic Table.

For simpicity, let’s round all the elments to 1 For simpicity, let’s round all the elments to 1 decimal point.decimal point.

What is the mass of sodium? Iron? Krypton? What is the mass of sodium? Iron? Krypton? Tungsten? Uranium? Tungsten? Uranium?

Mass of a CompoundMass of a Compound“gram formula mass” (for ionic compounds) or “gram molecular “gram formula mass” (for ionic compounds) or “gram molecular mass” (for molecular compounds) or just a generic “Molar Mass.”mass” (for molecular compounds) or just a generic “Molar Mass.”

There are no compounds on the Periodic Table.There are no compounds on the Periodic Table.

So you take the mass of each element, So you take the mass of each element, multiply that times the subscript for that multiply that times the subscript for that element and then add everything together to element and then add everything together to get the mass of the compound.get the mass of the compound.

Ex: mass of COEx: mass of CO22 = 12 + 16 x 2 = 12 + 32 = 44 = 12 + 16 x 2 = 12 + 32 = 44

What is the mass of water (HWhat is the mass of water (H22O)? Rust (FeO)? Rust (Fe22OO33)? )? Table Sugar (sucrose = CTable Sugar (sucrose = C1212HH2222OO1111)? Salt (NaCl)?)? Salt (NaCl)?

Power Point AssignmentPower Point Assignment

If your last name ends in A-LIf your last name ends in A-L Pg 181, 12-14 (a and b only)Pg 181, 12-14 (a and b only) Pg 198, 46 (b and d), 48, 50 (b, d and f)Pg 198, 46 (b and d), 48, 50 (b, d and f)

If your last name ends in M-ZIf your last name ends in M-Z Pg 181, 12-14 (b and c for 12; c and d for 13 and Pg 181, 12-14 (b and c for 12; c and d for 13 and

14)14) Pg 198, 46 (a and c), 48, 50 (a, c and e)Pg 198, 46 (a and c), 48, 50 (a, c and e)

Both groups be prepared for a one-question Both groups be prepared for a one-question quiz on Chapter 7 material in this powerpoint.quiz on Chapter 7 material in this powerpoint.

The EndThe End

What is next?What is next?

Well, Chapter 5, 28, 13, and 14.Well, Chapter 5, 28, 13, and 14.

If you are in advanced Chemistry, we are going to do all of If you are in advanced Chemistry, we are going to do all of those in Unit 2 (5&28) and 3 (13&14)those in Unit 2 (5&28) and 3 (13&14)

If you are in Chemistry, it’s mostly going to be Chapter 5, with If you are in Chemistry, it’s mostly going to be Chapter 5, with a little bit of all the others thrown in. We are going to skip a little bit of all the others thrown in. We are going to skip quite a lot in 28, 13 and 14, however.quite a lot in 28, 13 and 14, however.

chapter 3 & a li’l bit about “moles” chapter 3 & a li’l bit about “moles” plus...

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