LABORATORY SAFETY

Keep all books, backpacks, coats, etc. off of the lab benchesNo eating or drinking in the lab roomWear goggles, a lab coat, gloves, and covered shoes when working with chemicalsKnow the location of the following safety equipment:

Fire Extinguisher – to the left of the white board in the front of the lab roomEye Wash – to the right of the white board in the front of the lab roomSafety Shower – to the right of the white board in the front of the lab room

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Wash chemicals off of your skin with large amounts of waterClean all spills and breaks immediatelyNever use flames around flammable liquids (such as acetone)Always pour Acid Into WaterWaft to determine odors of chemicalsHeat test tubes on a slant, and not at the very bottomDispose of hazardous chemicals in waste bottles

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LABORATORY EQUIPMENT

Know the equipment on pages 6 and 7 of your Activity 1Know the following glassware accuracies:

volumetric flaskpipet, buretgraduated cylinderbeaker, Erlenmeyer flask

For accurate work : use pipets or buretsFor approximate work : use graduated cylindersFor storing liquids : use beakers or Erlenmeyer flasks

most accurate

least accurate

1A-3

CHAPTER 1 – CHEMISTRY: AN INTRODUCTION

CHEMISTRY – The study of materials and the changes they undergo

1A-4

M 10n

number of places decimal point is moved

number between 1 and 10

SCIENTIFIC NOTATION – The expression of a number as the product of a number between 1 and 10 and the appropriate power of 10

1A-5

CHAPTER 2 – MEASURMENTS AND CALCULATIONS

3.65 × 102 4.387 × 103 5.833 × 101

365 4,387 58.33

7.91 × 10-2 3.20 × 10-3 1.62 × 100

0.0791 0.00320 1.62

1A-6

UNITSScience uses the International System of units (SI) based on the metric system

Length Meter (m)Mass Gram (g)Volume Liter (L)

( = 39.37 inches)( = 0.035274 ounces)( = 1.060 quarts)

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METRIC PREFIXESPrefix Symbol Base Unit Multiplying Factormega M 106

kilo k 103

BASE UNIT 100

deci d 10-1

centi c 10-2

milli m 10-3

micro μ 10-6

nano n 10-9

1 m = m

1 m = m 1 m = m

John McClane

1A-8

Yippe-kai-ay,BUMF

1 liter = 1 dm3

1 mL = 1 cm3

= 1 cc

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MAKING MEASUREMENTS

best estimate is 6.7 cm

The “6” is known accurately because the closest divisions are “ones”The “0.7” is estimated because there are no divisions for “tenths”When making a measurement, record every digit known accurately, and then one digit that is estimated

Closest divisions: 1 cm each

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SIGNIFICANT FIGURES – The digits recorded in a measurement(all the certain digits plus one uncertain digit)

best estimate is 6.7 cm

6.7 cm has 2 significant figures

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best estimate is 6.75 cm

The “6” and “0.7” are known accurately because the closest divisions are “tenths”The “0.05” is estimated because there are no divisions for “hundredths”

Closest divisions: 0.1 cm each

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best estimate is 6.75 cm

6.75 cm has 3 significant figures

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closest divisions:estimated place:reading:significant figures:

1 mL eachtenths place83.5 mL3

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closest divisions:estimated place:reading:significant figures:

0.1 mL eachhundredths place2.65 mL3

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closest divisions:estimate the: reading:significant figures:

1 mL eachtenths place54.0 mL3

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TOLERANCE – The accepted error when making multiple measurements with a measuring deviceManufacturers give the tolerance for many types of graduated measuring devicesThe reading on a graduated measuring device should be to the same decimal place as the tolerance

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given tolerances:readings:significant figures:

0.03 mL10.00 mL4

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Significant figures are determined only for measurements, not for

(1) Counted numbers(28 students enrolled)

(2) Defined numbers(1 km = 103 m)(I hr = 60 min)

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RULES FOR COUNTING SIGNIFICANT FIGURES

(1) All nonzero digits are significant596 24.75 3,941 .8763 4 4 3

(2) Zeros that start a number are not significant0.021 0.0035 0.0908 0.467

2 2 3 3

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(3) Zeros that end a number without a decimal point are not significant300 2,700 16.0 40.00

1 2 3 4

401 2 3 4

40. 40.0 40.00

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uncertain in

“ones” place

uncertain in

“tens” place

uncertain in

“tenths” place

uncertain in

“hundredths” place

40 ± 10 40. ± 1 40.0 ± 0.1 40.00 ± 0.01

A non-significant zero can be made significant with a bar over it

1 2 3 4

_300

_300 300.0

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300

300 ± 10 300 ± 1 300 ± 0.1300 ± 100

12.3 12.370 0.00524 0.00103 5 3 2

600 23.00 3,019 43,1001 4 4 3

1,600. 0.00313 19.027 0.072044 3 5 4

1A-23

When writing a measurement in scientific notation, only significant figures are shown _

680 680 680.0

6.8 × 102 6.80 × 102 6.800 × 102

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2 3 4

1) ADDING AND SUBTRACTING MEASUREMENTS

The answer’s last digit will be in the same place as the last digit in the least accurate measurement

20.63 mL+ 6.6 mL

_______________

Accurate to the hundredthsAccurate to the tenths

27.23 mL

27.2 mL

Must round to the tenthsIf the last digit removed is 0 to 4, do not round up← Correct answer

36

OPERATIONS WITH MEASUREMENTS

3

1A-25

1.84 g+ 0.576 g

_______________

Accurate to the hundredthsAccurate to the thousandths

2.416 g

2.42 g

Must round to the hundredthsIf the last digit removed is 5 to 9, round up← Correct answer

4 6

1.84 g + 0.576 g

6

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12.57 cm13 cm

9 cm0.07 cm

+ 3.5 cm _______________

Accurate to the onesAccurate to the hundredthsAccurate to the tenths

Must round to the ones← Correct answer

9 7

9 cm + 0.07 cm + 3.5 cm

5

1A-27

32.3 m2

- 15.61 m2

_______________

Accurate to the tenthsAccurate to the hundredths

16.69 m2

16.7 m2

Must round to the tenths← Correct answer

3 1

32.3 m2 - 15.61 m2

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= 867.224 m2

= 867 m2 ← Correct answer

2) MULTIPLYING AND DIVIDING MEASUREMENTS

The number of sig fig’s in the answer will equal the number of sig fig’s in the measurement with the least number of sig fig’s

17.2 m x 50.42 m

Sig Fig’s: 3 4 Answer will have 3 sig fig’s

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= 0.0018075 cm3

= 0.002 cm3 ← Correct answer

2.41 cm x 0.003 cm x 0.25 cm

Sig Fig’s: 1 2 Answer will have 1 sig fig3

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(2.1 103 kW)(3.65 102 h)

Sig Fig’s: 2 3 Answer will have 2 sig fig’s

= 7.665 105 kWh

= 7.7 105 kWh ← Correct answer

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150. m 0.070 s

Sig Fig’s: 3 2 Answer will have 2 sig fig’s

= 2,142.857143 m/s

= 2,100 m/s ← Correct answer

1A-32