Explain why a knowledge of chemistry is central to many human
endeavors.
List and describe the steps of the scientific method.
Explain the basic safety rules that must be followed when working in the
chem lab.
Identify the metric units of measurement used in chemistry.
Explain what causes uncertainty in measurements.
Compare accuracy and precision.
Explain how to use significant figures and scientific notation.
Calculate percent error.
Define density and explain how it is calculated.
Explain how dimensional analysis and conversion factors are used to
solve problems in chemistry.












Chemistry
Scientific method
Observation
Hypothesis
Experiment
Conclusion
Natural law
Theory
Variable
Experimental control
Metric system
International System of
Units (SI)












Base unit
Mass
Volume
Metric prefix
Precision
Accepted unit
Accuracy
Significant digit
Percent error
Density
Dimensional analysis
Conversion factor

Look at the pic on p. 2
and read the caption
Name some of the basic
chemical substances
that make up your
body.
 Name some other
chemical processes,
besides digestion, that
occur in your body.
 Can you think of an
important chemical
reaction that occurs in
plants and trees?

What is Chemistry?


Chemistry is a broad science that touches
nearly every aspect of human life.
What are some ways chemistry affects the 2
careers mentioned in the section?


Examining a wetlands habitat
Preserving historical artifacts


Chemistry has been called the central science
b/c it overlaps so many sciences
Careers that use chemistry





Hair stylists
Construction
Biologists
What others?
Possible chemistry careers



Police departments (CSI)
Perfume companies
Research chemists


It is involved in many aspects of life
Helps you to understand the world around you

Read the “Connection” box on p. 6



What occupation is using chemistry?
What did they do to clean the art?
Why are some people upset about their actions?
The Scientific Method


A way of answering
questions about the
world we live in
Oscar
Has
Extremely
Colorful
TShirts
Observation
Question
Hypothesis
Experiment
Conclusion
Theory
(Model)
Theory
modified
as
needed
Prediction
Experiment
Natural
Law


Seeing a problem or asking a question that you
cannot answer
Always leads to a question



An educated guess
Usually asked in a “cause-effect” statement
Must be able to test the hypothesis



A test of the
hypothesis
Data will be collected
and analyzed
Must have 1 variable
and at least 1 constant

Variable – the
particular factor
being tested


The result of the analyzed data
May agree or disagree with your hypothesis


Answers the original question as well as any
others formed during the process
Predicts the results of further experiments

Describes how nature behaves but not why

On looseleaf to turn
in, page 13 (1-5)


With your small group, complete the
SpongeBob worksheet
SpongeBob Scientific Method.pdf
Safety in the Lab
Units of Measurement

Measurement: always includes a number and
unit


If someone is 7 feet tall, “7” is the number and “feet”
is the unit
Saying someone is 7 does not tell you enough info
 They could be 7 yrs old, 7 feet tall, 7 inches tall, …


Feet and inches are part of the English system
of measurement
In science, we use the Metric system

All scientists, no matter their country or language,
use the metric system
United States, Liberia, and Burma


SI units used by all scientists around the world
Based on 7 metric units called base units
Length
 Mass
 Time
 Count/Quantity
 Temperature
 Electric Current
 Luminous Intensity

meter (m)
kilogram (kg)
second (s)
mole (mol)
Kelvin (K)
ampere (A)
candela (cd)
Area
Volume
Force
Pressure
Energy
Power
Voltage
Frequency
Electric charge
square meter (m2)
cubic meter (m3)
Newton (N)
Pascal (Pa)
joule ( J )
watt (W)
volt (V)
hertz (Hz)
coulomb (C)


Science is a process, not a collection of rules
The most frequently used units in class that
differ than SI:
Temperature - Celsius (˚C)
 Volume – liter (L)
 Pressure – atmosphere (atm)
millimeters of mercury (mmHg)
 Energy – calorie (cal)


Length




Mass



A dime is 1 mm thick
A quarter is 2.5 cm in diameter
Average height of a man is 1.8 m
A nickel has a mass of 5 g
A 120 lb woman has a mass of about 55 kg
Volume


A 20 oz can of soda has a volume of 360 mL
A ½ gallon of milk is equal to 2 L
Prefix
Abbreviation
kilo-
k
1 000
hecta-
H
100
deca-
D
10
Base Unit
Meaning

1
deci-
d
0.1
centi-
c
0.01
milli-
m
0.001
King
Henry
Died
by
drinking
chocolate
milk
Base units include meter, liter, second, gram
kilohectodecaBase
units
decicentimilli-
How many millimeters are in a meter? 1 meter =
mm
1 meter = 1000 mm
kilohectodecabase
units
decicentimilli-

Convert a volume of 16 deciliters into liters


Convert 1.45 meters into centimeters


145 cm
Convert a volume of 8 deciliters into liters


1.6 L
0.8 L
Is 5 centimeters longer or shorter than 8
millimeters? Explain.

5 cm is longer than 8 mm b/c 0.05 m is greater than
0.008m
Worksheet
Uncertainty in Measurement

When making a measurement, write down
everything given to you with one uncertain
estimated number



5.1 inches is easy to spot but we still
need 1 uncertain number
My estimation = 5.12 inches
Measurements are uncertain b/c:


Measuring instruments are never completely free of
flaws
Measuring always involves some estimation



Precision: the same result is given over and
over under the same conditions
Accuracy: the result is close to a reliable
standard
Accepted value: the reliable standard
High Precision
High Accuracy
Working with Numbers



Measurements are rarely used just by
themselves.
Usually used in some form of mathematics (+, , x, or ÷)
Produces values of mass, temperature, volume,
etc.

The certain digits and the estimated digit of a
measurement

Example: In the # 31.7, there are 3 sig figs
 The 3 and 1 are certain digits while the 7 is the
uncertain digit

Nonzero #: any number that is not a zero


1, 2, 3, 4, 5, 6, 7, 8, or 9
Zeros

Never count “leading zeros”
 0023  only count the 2 and 3
 0.054  only count the 5 and 4

Always count “captive” or “sandwiched” zeros
 303  count the 3, 0, and 3

“Trailing zeros”: zeros to the right
 Only count if used with a decimal point
 5400  only count the 5 and 4
 5.400  count the 5, 4, 0, and 0

How many sig figs are in 0.057 010 g?

Nonzero numbers:
 0.057 010

Captive zeros
 0.057 010

Trailing zeros when there is a decimal
 0.057 010

Final Answer
 0.057 010
 5 significant figures

How many sig figs in the following numbers?







0.002 6701 m
 5 sig figs
0.002 6701
 6 sig figs
19.0550
 2 sig figs
3500
 4 sig figs
1 809 000
 3 sig figs
95 600
 2 sig figs
520
 3 sig figs
0.0102
19.0550 kg
3500 V
1 809 000 L
95 600 m
520 mL
0.0102 ms

Multiplying and Dividing
The answer will have the same # of sig figs as
the measurement with the smallest # of sig
figs
 Volume = 3.052 m x 2.10 m x 0.75 m

(4 sig figs)
(3 sig figs)
= 4.8069 m3
= 4.8 m3
(2 sig figs)

Adding and Subtracting




The answer will have the same # of decimal places as
the measurement with the smallest # of decimal
places
951.0 g
1407
g
23.911 g
+ 158.18 g
2540.091 g
Since there aren’t any decimals in 1407, our answer
will not have decimals
Final answer = 2540 g

6.15 m x 4.026 m =


1.45 m x 1.355 m x 2.03 m =


3.9884425 m3 = 3.99 m3
0.3287 g + 45.2 g =


24.7599 m2 = 24.8 m2
45.5287 g = 45.5 g
0.258 mL ÷ 0.361 05 mL =

0.71458246 mL = 0.715 mL
Worksheet


In science we work w/ very large and very
small #s
For example:


1 drop of water contains =
1,700,000,000,000,000,000,000 molecules
The mass of 1 proton =
0.000 000 000 000 000 000 000 000 001 672 62 kg

To make it easier for ourselves, we use
scientific notation
1 drop of water contains =
1,700,000,000,000,000,000,000 molecules
 1 drop of water contains = 1.7 x 1021
 The mass of 1 proton =
0.000 000 000 000 000 000 000 000 001 672 62 kg
 The mass of 1 proton = 1.67262 x 10-21

Write 1700 in scientific notation

Write down the full number

1700

Move the decimal until it is right after the first 1-10
number

1700  1700.  1.700

Write down this new number without the zeros

1.7

Place “x 10” after this number

1.7 x 10

Count how many times you had to move the decimal
and place that number after the 10 as an exponent




If you move to the right = negative exponent
If you move to the left = positive exponent
1.7 x 103

37 700


1 024 000


3.901 x 10-9
8960


1.024 x 106
0.000 000 003 901


3.77 x 104
8.96 x 103
0.000 23

2.3 x 10-4

Data will often be
given as a percent


If it is a fraction, just
divide and multiply
by 100
Ex: 900 million
kilograms of plastic
soft drink bottles are
produced each year.
180 million kilograms
of them are recycled.
180 million kilograms = 0.2 x 100% = 20%
900 million kilograms


A measurement can be compared to its
accepted value by finding the percent error
% error can be positive or negative
Positive = measured value is greater than accepted
 Negative = measured value is less than accepted

% error =
measured value – accepted value
accepted value
x 100%



In an experiment dealing with finding the boiling point
of water, you performed 3 experiments and found
water to boil at 98.4˚C, 98.9 ˚C, and 97.5˚C. What is the
average and % error of your data? (Hint: the accepted
value of the boiling point of water is 100˚C)
98.4 + 98.9 + 97.5 = 294.8 / 3 = 98.3
% error = (100 – 98.3) / 100 x 100 = 1.7%
Work the problems on your “Accuracy Precision and
Percent Error” worksheet from a few class periods ago

Density – compares
the mass of an object
to its volume

measured in:
 grams per cubic
centimeters (g/cm3)
 grams per milliliter
(g/mL)
Mass
Density =
Volume


If a sample of aluminum has a mass of 13.5g
and a volume of 5.0 cm3, what is its density?
2.7 g/cm3


Suppose a sample of aluminum is placed in a
25 mL graduated cylinder containing 10.5 mL
of water. The level of the water rises to 13.5
mL. What is the mass of the aluminum
sample? (Use the density you found in the problem before this)
8.1 g


A piece of metal with a mass of 147g is placed
in a 50mL graduated cylinder. The water level
rises from 20mL to 41mL. What is the density
of the metal?
7 g/mL


What is the volume of a sample that has a mass
of 20g and a density of 4g/mL?
5 mL


A metal cube has a mass of 20g and a volume
of 5cm3. Is the cube made of pure aluminum?
Explain. (Hint: Pure Aluminum will have a
density of 2.7g/cm3.)
4 g/cm3


Technique of converting between units
How many feet are in 86 centimeters?


We know 12 inches = 1 foot
We also know 1 inch = 2.54 centimeters
86 cm
1 in
2.54 cm
1 ft
12 in
= 2.82 ft


Use Fig 1-29 on page 38 to help you solve the
following problems
How many cubic centimeters are in 2.3 gal?


How many meters are in 3.5 mi?


103 000 Pa
How many seconds are in 10.5 hours?


5 600 m
How many pascals are in 770 mm Hg?


8 700 cm3
37 800 s
How many days are in 12 583 seconds?

0.14564 days

How to draw a scientific graph

Need independent variable (x – axis)
 the variable being changed

Need dependent variable (y – axis)
 the variable being changed by the independent variable



Label each axis
Do not connect each dot, use a “line of best fit”
Give the graph a title which tells what it is of

A balloon is filled with air and attached to the
bottom of a large container of water. If the
water temperature is changed, by heating or
adding ice, the volume of the air in the balloon
also changes. Data was collected from taking
volume measurements at different
temperatures.


Independent variable: temperature
Dependent variable: volume
Trial
Temperature
(˚C)
Volume
(mL)
1
25
101.3
2
30
103.2
3
35
103.4
112
4
40
105.0
110
5
45
106.7
108
6
50
108.4
106
7
55
110.0
8
60
111.5
104
9
65
112.9
10
70
114.2
Volume (mL)
116
114
102
100
0
20
40
60
80