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Warmup (5 min). Have your packet out!. 1. 10 3 / 10 -4 = 2. (10 19 ) (10 2 ) = 3. Round 5.678 to 3 digits 4. 16 = 3.0 5. (56.8)(6.0) =. All answers will be discussed during lecture, but see if you can do these NOW!. *You will need a calculator today.

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Warmup (5 min)

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Warmup 5 min

Warmup (5 min)

Have your packet out!

1. 103 / 10-4 =

2. (1019) (102) =

3. Round 5.678 to 3 digits

4. 16 =

3.0

5. (56.8)(6.0) =

All answers will be discussed during lecture, but see if you can do these NOW!

*You will need a calculator today.


Introduction to quantitative chemistry significant figures rounding scientific notation

Introduction to Quantitative ChemistrySignificant FiguresRoundingScientific Notation

Take notes on Introduction to Quantitative Chemistry Notes/Problems and ALSO on a separate sheet of paper


Warmup 5 min

Quantitative ObservationsQualitative Observations

Involves measured Involves general

values and numbers observations without

examples? measurement

Ex. It is 36.7⁰C outside today

The river is 31.5 m deep

The cheese costs $4.25 per pound

Ex. It is hot today

The building is tall

I do not weigh a lot


Warmup 5 min

What are significant figures? (‘sig figs’)

“Important numbers”?!?!?!

11.818 sec vs 12.000 sec? Who cares?

In swimming/track, the stopwatch is VERY precise

  • There is a reason for placing zeros in a measured value when they are not important for calculation purposes. Significant does not mean IMPORTANT.

  • The number of sig figs reported in a value implied the degree of precision of the instrument used to make the measurement.


Warmup 5 min

Which digits are significant?

0.00450600


With a partner take 2 minutes to discuss how many significant figures are in each of these values

With a partner, take 2 minutes to discuss how many significant figures are in each of these values:

3

2

1) 1908

2) 0.0025

3) 15.9

5

5

1

4) 0.7040

5) 340.06

6) 140. vs 140.0 vs 140


P acific a tlantic decimal p resent decimal a bsent

Pacific Atlanticdecimal presentdecimal absent

0.00805

100800

4.000100

2000

3

4

7

1

Pick your ocean

Skip zeros, find first 1-9 digit

Count all digits, even the zeros


Warmup 5 min

Round these values to four significant figures:

  • 0.0587920b. 1670.48564 c. 3450824

    a. 0.05879 b. 1670. c. 3451000

    Rules for Rounding:

  • If the digit to be removed is < 5, the preceding digit remains unchanged

    Ex. 25.44 rounds to 25.4

  • If the digit to be removed is ≥ 5, then the preceding digit is increased by 1

    Ex. 25.46 rounds to 25.5


Perform each operation and round answers to the appropriate number of sig figs

16 = b. (56.8)(6.0) =

3.0

c. 590.0 = d. (324.6)(815.991) =

611

Perform each operation and round answers to the appropriate number of sig figs

340

5.3

0.966

264900

Rules1) To see how many sig figs to use in your answer, look at the # sig figs in the values given to you in the problem.2) If the starting values have different numbers of sig figs, use the lower # of sig figs


Warmup 5 min

7.442

- 7.429

0.013

c. 16.82

+ 3.2257

20.0457

20.05

Perform the indicated calculations on the following measured values, giving the final answer with the correct number of significant figures.

  • 2.86

    + 3.4921

    + 1.3

    7.6521

    7.7

Round to the last digit that they have in common. I will sometimes break this rule for one reason or another…… just go with it.


Warmup 5 min

Scientific notation is used to simplify very small or large numbers. It expresses a number as:

  • a number between 1 and 10 and

    2) a power of 10

    Ex. 6780  6.780 x 103

    PART 1: Identifying correct scientific notation

    Which of these numbers are/are not written in correct scientific notation?

    3.57 x 10-8 4.23 x 10-275.3 x 10-10

    2.92 x 109 0.00345 x 104

Gross!


Warmup 5 min

Move the decimal to the right, exponent = negative

0.00032  3.2 x 10-4

PART 2: Changing a value into scientific notation

Move the decimal to the

left, exponent = positive.

32000  3.2 x 104

a. Change 0.00045 to scientific notation

b. Express 1.28 x 10-5 in standard (regular) notation

a. 4.5 x 10-4b. 0.0000128

Put the following values into scientific notation using 3 significant figures:

1) 0.00980 3) 25900.0

2) 10.5 4) 0.043

2.59 x 104

9.80 x 10-3

1.05 x 101

4.30 x 10-2


Warmup 5 min

5 x 10-3

4

0.0015

1 x 106

5.05 x 103

0.00000335

220000

2.5 x 10-4

Take 3 minutes to fill in the missing pieces from this chart


Warmup 5 min

PART 3 Multiplying, dividing numbers in scientific notation

Ex A: (2.5 x 105)(2.0 x10-2)

= 5.0 x 103

Ex B: 6.8 x 107

1.7 x 103

 ****make sure to group values in your calculator using parenthesis!!!!!!!!!!!!!!

= 4.0 x 104 (add a zero bc you need 2 sig figs)

( )


Warmup 5 min

1.78 x 10-11

7.37 x 103

Do the last 5 on your own. I will give answers in 3 minutes.

1. (8.31 x 10-1)(2.14 x10-11) = 2. (3.51 x 10-3)(2.10 x106) =

3. 9.1 x 104 =4. (5.9 x 104) =

11 x 108 (7.2 x 10-3)

5. (5.5 x 104) (1.1 x106) =

(3.2 x 108)

8.2 x 106

8.3 x 10-5

1.9 x 102


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