applied chemistry scientific measurements in this chapter, will apply the scientific method to...

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APPLIED CHEMISTRY SCIENTIFIC MEASUREMENTS In this chapter, will apply the scientific method to various problems and use experiments to prove hypotheses. You will also learn the basic mathematical skills needed to succeed in chemistry.

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Page 1: APPLIED CHEMISTRY SCIENTIFIC MEASUREMENTS In this chapter, will apply the scientific method to various problems and use experiments to prove hypotheses

APPLIED CHEMISTRY SCIENTIFIC MEASUREMENTS

In this chapter, will apply the scientific method to various problems and use experiments to prove

hypotheses. You will also learn the basic mathematical skills needed to succeed in

chemistry.

Page 2: APPLIED CHEMISTRY SCIENTIFIC MEASUREMENTS In this chapter, will apply the scientific method to various problems and use experiments to prove hypotheses

is also known as the central science

• Chemists are employed in dozens of occupations

• Whatever your career choice is, chances are you will need some

knowledge of chemistry!!!!

Page 3: APPLIED CHEMISTRY SCIENTIFIC MEASUREMENTS In this chapter, will apply the scientific method to various problems and use experiments to prove hypotheses

The Scientific Method

Page 4: APPLIED CHEMISTRY SCIENTIFIC MEASUREMENTS In this chapter, will apply the scientific method to various problems and use experiments to prove hypotheses

Hypothesis: A Testable Prediction

• If…then… statement

• Narrow—tests one, and only one, thing

Example 1: The static on your radio increases right before it thunders during a storm.

Example 2: People who smoke cough more than people who don’t smoke.

Page 5: APPLIED CHEMISTRY SCIENTIFIC MEASUREMENTS In this chapter, will apply the scientific method to various problems and use experiments to prove hypotheses

Hypothesis: A Testable Prediction

• If…then… statement

• Narrow—tests one, and only one, thing

Example 3: You sneeze every time you visit your best friend’s house.

Example 4: On a cold morning, the air pressure in the tires of your car measures 34 psi. After several hours of high-speed driving, the pressure measures 38 psi.

Page 6: APPLIED CHEMISTRY SCIENTIFIC MEASUREMENTS In this chapter, will apply the scientific method to various problems and use experiments to prove hypotheses

EXPERIMENT

Variable: The factor being tested in an experiment

• Independent Variable: The factor that you change/adjust in the experiment

• Dependent Variable: The factor that changes due to changes in the independent variable.

Page 7: APPLIED CHEMISTRY SCIENTIFIC MEASUREMENTS In this chapter, will apply the scientific method to various problems and use experiments to prove hypotheses

EXPERIMENT

Control: Factor that responds in a predictable way to the experiment

– A control is what the rest of the experiment can be compared to

Constant: Factor(s) that do

not change during the

experiment.

Page 8: APPLIED CHEMISTRY SCIENTIFIC MEASUREMENTS In this chapter, will apply the scientific method to various problems and use experiments to prove hypotheses

• Independent Variable:• Dependent Variable:• Control:• Constant:

EXPERIMENT

Pea plant clones are given different amounts of water for a 3 week period. The first plant receives 400 mL a day. The second pea plant receives 200 mL a day. The third pea plant receives 100 mL a day. The fourth pea plant does not receive any extra water, the plant only receives natural ways of receiving water. The height of the pea plants is recorded daily.

Page 9: APPLIED CHEMISTRY SCIENTIFIC MEASUREMENTS In this chapter, will apply the scientific method to various problems and use experiments to prove hypotheses

• Independent Variable:• Dependent Variable:• Control:• Constant:

EXPERIMENT

You want to test which size ball is easiest to juggle. You test a baseball, a softball, a soccer ball and a basketball. You count the seconds you can continuously juggle each type of ball.

You want to determine which classroom is the hottest one in the school.

• Independent Variable:• Dependent Variable:• Control:• Constant:

Page 10: APPLIED CHEMISTRY SCIENTIFIC MEASUREMENTS In this chapter, will apply the scientific method to various problems and use experiments to prove hypotheses

• Data: Recorded Observations

Qualitative: observation made with 5 senses

Example:

Quantitative: measured observation (# & unit)

Example:

Page 11: APPLIED CHEMISTRY SCIENTIFIC MEASUREMENTS In this chapter, will apply the scientific method to various problems and use experiments to prove hypotheses

Data Table: Only includes the 2 variables’ data

Independent VariableDependent Variable

Page 12: APPLIED CHEMISTRY SCIENTIFIC MEASUREMENTS In this chapter, will apply the scientific method to various problems and use experiments to prove hypotheses

Graph: a visual Graph: a visual representation of datarepresentation of data

x-axis: the horizontal axisx-axis: the horizontal axis Independent Variable: The factor in the Independent Variable: The factor in the

experiment that the experimenter experiment that the experimenter changes.changes.

y-axis: the vertical axisy-axis: the vertical axis Dependent Variable: The factor that Dependent Variable: The factor that

changes due to changes in the changes due to changes in the independent variable.independent variable.

Page 13: APPLIED CHEMISTRY SCIENTIFIC MEASUREMENTS In this chapter, will apply the scientific method to various problems and use experiments to prove hypotheses

Y-a

xis

x-axis

Page 14: APPLIED CHEMISTRY SCIENTIFIC MEASUREMENTS In this chapter, will apply the scientific method to various problems and use experiments to prove hypotheses

Graph:Graph: a visual representation of data a visual representation of dataSteps to GraphingSteps to Graphing

Numbering: Make sure the numbers Numbering: Make sure the numbers you put on the axes follow patterns.you put on the axes follow patterns. For example: 2, 4, 6, 8, 10 or 5, 10, 15, For example: 2, 4, 6, 8, 10 or 5, 10, 15,

20 or 0.1, 0.2, 0.3, 0.4 etc.20 or 0.1, 0.2, 0.3, 0.4 etc. Labeling: Make sure you label each Labeling: Make sure you label each

axis with a title and a unit and that axis with a title and a unit and that you title your graph.you title your graph.

Page 15: APPLIED CHEMISTRY SCIENTIFIC MEASUREMENTS In this chapter, will apply the scientific method to various problems and use experiments to prove hypotheses

TrendsTrends

Best Fit Line: A straight line that Best Fit Line: A straight line that goes through the center of most goes through the center of most points.points.

Page 16: APPLIED CHEMISTRY SCIENTIFIC MEASUREMENTS In this chapter, will apply the scientific method to various problems and use experiments to prove hypotheses

Trends cont.Trends cont.

Inversely Proportional: As one Inversely Proportional: As one variable increases, the other variable increases, the other variable decreases.variable decreases.

Page 17: APPLIED CHEMISTRY SCIENTIFIC MEASUREMENTS In this chapter, will apply the scientific method to various problems and use experiments to prove hypotheses

Trends in GraphingTrends in Graphing

Directly Proportional: As one Directly Proportional: As one variable increases/decreases the variable increases/decreases the other does the sameother does the same

Page 18: APPLIED CHEMISTRY SCIENTIFIC MEASUREMENTS In this chapter, will apply the scientific method to various problems and use experiments to prove hypotheses

Y-a

xis

x-axis

Example: Create a line graph of the following data: Mass (g)Mass (g) Volume Volume (cm(cm33))

2525 100100

3030 115115

4040 134134

5050 160160

5454 163163

Page 19: APPLIED CHEMISTRY SCIENTIFIC MEASUREMENTS In this chapter, will apply the scientific method to various problems and use experiments to prove hypotheses

Density

20

25

30

3540

45

50

55

60

100 120 140 160

Volume (cm3)

Mas

s (g

)

Page 20: APPLIED CHEMISTRY SCIENTIFIC MEASUREMENTS In this chapter, will apply the scientific method to various problems and use experiments to prove hypotheses

Draw Conclusions

Theory: Explains

• States the “Why”

Law: States a Fact

• States the “What”

Page 21: APPLIED CHEMISTRY SCIENTIFIC MEASUREMENTS In this chapter, will apply the scientific method to various problems and use experiments to prove hypotheses

Uncertainty in Measurements

Why are measurements uncertain? Precision of instrumentation varies Human error

Page 22: APPLIED CHEMISTRY SCIENTIFIC MEASUREMENTS In this chapter, will apply the scientific method to various problems and use experiments to prove hypotheses

Reading Measurements The number of digits you should write

when writing down a measurement depends on the instrumentation you are using.

You should always include a number and a unit when writing down a measurement

When determining a measurement include all the digits you know for certain plus 1 more digit.

Page 23: APPLIED CHEMISTRY SCIENTIFIC MEASUREMENTS In this chapter, will apply the scientific method to various problems and use experiments to prove hypotheses

Significant Figures

All the digits you know for certain in a measurement plus

1 more estimated digit

Page 24: APPLIED CHEMISTRY SCIENTIFIC MEASUREMENTS In this chapter, will apply the scientific method to various problems and use experiments to prove hypotheses

Graduated Cylinder

Put the cylinder flat on the table and read at the bottom of the miniscus (bubble)

Page 25: APPLIED CHEMISTRY SCIENTIFIC MEASUREMENTS In this chapter, will apply the scientific method to various problems and use experiments to prove hypotheses

Ruler

Page 26: APPLIED CHEMISTRY SCIENTIFIC MEASUREMENTS In this chapter, will apply the scientific method to various problems and use experiments to prove hypotheses

Thermometer

Page 27: APPLIED CHEMISTRY SCIENTIFIC MEASUREMENTS In this chapter, will apply the scientific method to various problems and use experiments to prove hypotheses

What is the difference between precision & accuracy?

Page 28: APPLIED CHEMISTRY SCIENTIFIC MEASUREMENTS In this chapter, will apply the scientific method to various problems and use experiments to prove hypotheses

Precision Also called reproducibility or repeatibility Measurements are close to each other (getting

the same measurements each time)

Page 29: APPLIED CHEMISTRY SCIENTIFIC MEASUREMENTS In this chapter, will apply the scientific method to various problems and use experiments to prove hypotheses

Accuracy

Measurements are close to the actual value

Page 30: APPLIED CHEMISTRY SCIENTIFIC MEASUREMENTS In this chapter, will apply the scientific method to various problems and use experiments to prove hypotheses

PERCENT ERROR

Percent Error: |measured value – accepted value| x 100%

accepted value

You measure the classroom temperature to be 23C. The actual classroom temperature is 20 C. What is your percent error?

Page 31: APPLIED CHEMISTRY SCIENTIFIC MEASUREMENTS In this chapter, will apply the scientific method to various problems and use experiments to prove hypotheses

ROUNDING The first digit is always the 1st non-zero digit

in the number. Count the appropriate # of digits, if the

next number is 5 or greater, round the last number up 1. If not, do nothing. Examples:

2.3344(1)1.029 (3)0.00234(2)

Page 32: APPLIED CHEMISTRY SCIENTIFIC MEASUREMENTS In this chapter, will apply the scientific method to various problems and use experiments to prove hypotheses

Scientific Notation

A number is written in 2 parts. The first part is a number between 1 & 10 The second part is a power of ten

Exponent Positive exponents represent numbers

greater than 1 Negative exponents represent numbers

less than 1

Page 33: APPLIED CHEMISTRY SCIENTIFIC MEASUREMENTS In this chapter, will apply the scientific method to various problems and use experiments to prove hypotheses

Scientific Notation

To convert a number to scientific notation: Count how many places the decimal place must be moved to

make the number a number between 1 & 10 (the coefficient) The number of spaces the decimal moved is the value of the

exponent If you moved the decimal to the right, the exponent is

negative If you moved the decimal to the left, the exponent is positive Write: Coefficient x 10exponent

Page 34: APPLIED CHEMISTRY SCIENTIFIC MEASUREMENTS In this chapter, will apply the scientific method to various problems and use experiments to prove hypotheses

Scientific Notation To convert a number from scientific

notation to regular notation: If the exponent is positive, move the decimal

in the coefficient the number of spaces indicated by the exponent to the right

If the exponent is negative, move the decimal in the coefficient the number of spaces indicated by the exponent to the left.

Page 35: APPLIED CHEMISTRY SCIENTIFIC MEASUREMENTS In this chapter, will apply the scientific method to various problems and use experiments to prove hypotheses

Scientific Notation

Example 1: Convert the following numbers to scientific notation.0.000035 = 2,020.00 =

2,100,000 =

Example 2: Express each of the following numbers in regular notation.6.7 x 10-3 = 3 x 105 =

2.100 x 103 =

Page 36: APPLIED CHEMISTRY SCIENTIFIC MEASUREMENTS In this chapter, will apply the scientific method to various problems and use experiments to prove hypotheses

Scientific Notation

(1.2 x 10-3) x (2.2 x 105) =

(6.2 x 10-3) (2.1 x 10-3) =

(1.345 x 105) + (2.23 x 106) =

200 x 3 x 10-3 =

Page 37: APPLIED CHEMISTRY SCIENTIFIC MEASUREMENTS In this chapter, will apply the scientific method to various problems and use experiments to prove hypotheses

What do the countries in red have in common?

Page 38: APPLIED CHEMISTRY SCIENTIFIC MEASUREMENTS In this chapter, will apply the scientific method to various problems and use experiments to prove hypotheses

International System of Units (SI Units)

• A revised version of the metric system that was developed in France in 1795 and was adopted by international agreement in 1960

• There are 7 base SI units– All other SI Units are DERIVED from the 7

base units

Page 39: APPLIED CHEMISTRY SCIENTIFIC MEASUREMENTS In this chapter, will apply the scientific method to various problems and use experiments to prove hypotheses

Base Units: The 7 metric units that SI is built upon

Physical Quantity

Unit Name Unit Symbol Measured using…

Mass Kilogram kg Balance

Length Meter m Meterstick/Ruler

Time Second s Stopwatch

Quantity Mole mol varies

Temperature Kelvin K thermometer

Electric Current Ampere A Ammeter

Luminous Intensity

Candela cd Photometer

Page 40: APPLIED CHEMISTRY SCIENTIFIC MEASUREMENTS In this chapter, will apply the scientific method to various problems and use experiments to prove hypotheses

NON-SI UNITS

Physical Quantity Unit Name Unit Symbol

Volume Liter L

Pressure Pascal

Atmosphere

Pa

Atm

Temperature Celsius C

Energy Joule J

Page 41: APPLIED CHEMISTRY SCIENTIFIC MEASUREMENTS In this chapter, will apply the scientific method to various problems and use experiments to prove hypotheses

Derived Units Commonly Used in Chemistry

Physical Quantity

How to Calculate Unit Name Unit Symbol

Volume

Area

Density

To Derive a Unit• Write the mathematical formula for the quantity.• Replace the formula with units and simplify.

Page 42: APPLIED CHEMISTRY SCIENTIFIC MEASUREMENTS In this chapter, will apply the scientific method to various problems and use experiments to prove hypotheses

Temperature

• Measured with: Fahrenheit Scale: An arbitrary scale created by Gabriel Fahrenheit.

F = (C 9/5) + 32

Celsius Scale: Based on the freezing and boiling points of water.

C = (F – 32) 5/9

C = K – 273

Kelvin Scale: The S.I. Scale

•Based on absolute zero.

Absolute Zero: The point at which the motion of particles of matter (their kinetic energy) ceases.

K = C + 273

Page 43: APPLIED CHEMISTRY SCIENTIFIC MEASUREMENTS In this chapter, will apply the scientific method to various problems and use experiments to prove hypotheses

METRIC CONVERSIONS

Page 44: APPLIED CHEMISTRY SCIENTIFIC MEASUREMENTS In this chapter, will apply the scientific method to various problems and use experiments to prove hypotheses

METRIC PREFIXESPREFIX In 1 base unit there

are:Example

mega- (M) 10-6 M-unit 1 m = 10-6 Mm

kilo- (k) 10-3 k-unit 1 L = 10-3 kL

deka- (dk) 0.1 dk-unit 1 g = 0.1 dkg

BASE UNIT

deci- (d) 10 d-unit 1 s = 10 ds

centi- (c) 100 c-unit 1 mol = 100 cmol

milli- (m) 1000 m-unit 1 m = 1000 mm

micro- () 106 -unit 1 L = 106 L

nano- (n) 109 n-unit 1 g = 109 ng

pico- (p) 1012 p-unit 1 s = 1012 ps

Page 45: APPLIED CHEMISTRY SCIENTIFIC MEASUREMENTS In this chapter, will apply the scientific method to various problems and use experiments to prove hypotheses

DIMENSIONAL ANALYSIS

What is dimensional analysis?

What is a unit equality?

What is a conversion factor?

What is a conversion factor equal to?

How do you use conversion factors?

Dimensional analysis is a method used to convert between units

A unit equality are two values that are equal to each other (like 3 ft = 1 yd)

A conversion factor is a ratio of a unit equality (3 ft/1yd)

1 (anything divided by an equal value is 1)

Multiply it to a number to convert between units

Page 46: APPLIED CHEMISTRY SCIENTIFIC MEASUREMENTS In this chapter, will apply the scientific method to various problems and use experiments to prove hypotheses

DIMENSIONAL ANALYSISSteps to Dimensional Analysis1. Start with what you know

(number and unit).2. Times a line.3. Add a conversion factor so that

units cancel and what you are looking for is on top of the ratio.

4. Check your answer. 1 Base Unit Equals

10-6 Mega-10-3 kilo-0.1 deka-10 deci-

100 centi-1000 milli-106 micro-109 nano-1012 pico-