Significant Figures 1. Have your notebook out. 2. Bring your Variables Worksheet up to be stamped

Significant Figures

1. Have your notebook out.

2. Bring your Variables Worksheet up to be stamped.

Homework Sig Figs Worksheet 1, due

Tonight, you will only be able to do problems #1-2. Leave problem #3 alone; you’ll be able to do it after tomorrow’s lesson.

Variables Worksheet Group corrections

Significant Figures Notebooks out! Title this section of your

notes “Significant Figures.”

Before you can begin collecting your data, you need to know the mathematical standards you’ll be held to…

Significant Figures The big ideas:

Scientists need to know how strong their measurements are. We use “significant figures” to show that strength.

The more significant figures a number has, the stronger the measurement it was.

Using better measurement tools gives you numbers with more sig figs.

There are rules for figuring out how many sig figs there are.

Significant Figures Say you want to measure this guy from

eartip to eartip.

QuickTime™ and a decompressor

are needed to see this picture.

Significant Figures Say you want to measure this guy from

eartip to eartip.



Significant Figures When you take a measurement, you

can estimate one extra digit beyond the ones on the instrument, but no more than one.

The better ruler gave us a more precise measurement.

Significant Figures The Rules! When you figure out sig

figs, always follow these rules in this order. Let’s practice on this number: 020,670.90

1. All digits NOT zero are always significant figures.

Significant Figures 020,670.90

2. Final zeroes after a decimal point are significant.

3. A zero between two significant numbers is significant.

4. All the zeroes that are left are NOT significant.

Sig Figs Practice How many sig figs?

0.00416


0.00416Rule 1: Underline all non-zeroes.Rule 2: Underline all zeroes trailing at the end after a decimal point.Rule 3: Underline all zeroes in between other underlined numbers.Rule 4: Cross out anything that’s left.


0.00416Rule 1: Underline all non-zeroes.Rule 2: Underline all zeroes trailing at the end after a decimal point.Rule 3: Underline all zeroes in between other underlined numbers.Rule 4: Cross out anything that’s left.

THREE SIG FIGS.


0.00416 =

5.18 =

200 =

200.0 =

Sig Figs Practice Mini-competition: A sticker to the pair that

gets the most right answers! You may use your notes.

3.0800 0.000054 91,106 76,000,000,000,000 0.00305 0.0080

Sig Figs Practice Come up with 10 significant figures problems,

at least five must include rounding. You must know the answers to them.

Write the problems on a fresh sheet of paper, and an answer key on another piece of paper. When you’re done, give your “sig fig quiz” to another group to solve. Check their answers when they’re done.

MORE fun with sig figs! (Sticker chance) How many sig figs are

in each of these numbers? 40.08 32.9000 928,301.1 500,000,000,000,000,000

Homework Sig Figs worksheet, due Friday for B

and Monday for F.

MORE fun with Sig Figs! What if somebody measured the area of an

aye-aye ear like this?



MORE fun with Sig Figs! A chain is no stronger than its weakest link.

One bad measurement makes your whole result bad.

When you add, subtract, multiply, or divide, you can never get more sig figs than the WORST of the numbers that you used.



MORE fun with Sig Figs! How many sig figs can each of these

answers have?

20 x 673


answers have?

20 x 673 = The answer must have 1 sig fig, since that is the worst of the numbers we started with.


answers have?

20 x 673 = 1 sig fig 0.041 x 248,200


answers have?

20 x 673 = 0.041 x 248,200 = 3.0800 / 0.003 =

Rounding Sig Figs What if the problem’s answer has too

many sig figs or places past the decimal? You must round it.

Take 20 x 673. We said that the answer must have just one sig fig. Here’s how to get there.

Rounding Sig Figs 1. Do the operation normally first.

What is 20 x 673?


20 x 673 = 13,460 . 2. Count off the number of sig figs that

you need, starting from the leftmost significant digit.


20 x 673 = 13,460 . 2. Count off the number of sig figs that

you need, starting from the leftmost significant digit.

3. The last digit that you count to must be rounded, the rest that you counted past will stay the same.

Rounding Sig Figs 20 x 673 = 13,460, which becomes

10,000

Try these problems: 8.9 x 10.8 . First, what normal answer do

you get?

Rounding Sig Figs 8.95 x 10.81 = 96.7495 Next, how many sig

figs do we have to get this number down to?

Starting with the leftmost significant digit (the 9) count off the sig figs you want, going towards the right. The number you land on is the number to round.

Rounding off 96.7495, we get…

Rounding Sig Figs How about adding and subtracting?

4.87 + 927.3

Sig Figs Practice

Try these problems: 30 / 81 90.4 - 0.08 27,483 + 94,780 2.33 x 6.085 x 2.2

Sig Figs Practice Like before, design a “quiz” for another

team. 8 questions.

Two questions, present a single number and ask how many sig figs it has.

Six questions, use multiplication, addition, etc.

Precision and Accuracy Pick up the handout.

Homework Twisted Rulers Analysis, go as far as

you can until you hit another (with class) question

Sig Figs What’s the point of caring about sig

figs?

Precision Precision = How exact your

measurement is.

Significant figures measure precision. The more significant figures you have, the more precise your measurement.

Is this the same thing as being right?

Precision & Accuracy Accuracy = How correct your measurement

is.

Different from precision, and not measured by sig figs!

What do I mean by that? Twisted Rulers lab will hopefully illustrate the idea!

Twisted Rulers Lab Groups of two tables. Share rulers amongst groups, use them in any

order, just be SURE you record data for the right letter!

Two volume stations. Instructions are at the stations. Learn to read

instructions out loud to the group before attempting the operation!

Graded for: correct sig figs (estimating past digits on rulers, multiplication). Feel free to check with me on your sig fig work.

Accuracy Accuracy = How correct your

measurement is.

Sig figs can’t tell you this. Instead, a procedure called percent error can.

Precision & Accuracy The equation for percent error (write it):

(Observed Value) - (Expected Value)

_______________________________ x 100

(Expected Value)

Documents

Significant Figures 1. Have your notebook out. 2. Bring your Variables Worksheet up to be stamped