Science = the study of the world around us. Knowledge of
the physical or material world gained through observation
and experimentation.
The Nature of Science
• Scientific law versus theory:
– Scientific law: a summary of an
observed natural event.
– Scientific theory: a well tested,
possible explanation of a natural event.
The Way Science Works…
• Science involves critical thinking, or applying
logic and reason to observations and
conclusions.
• Observation vs. Inference
– Observation: descriptive of what you see,
hear, taste, feel, smell
– Inference: an assumption made as a result
of an observation (not always correct!!)
Variables and Controls
• A variable is anything that can change in an
experiment.
– Independent variable: The variable being changed
or controlled by the scientist.
– Dependent variable: The variable being measured
or observed by the scientist.
• A controlled experiment tests only one variable at a
time.
The Scientific Method:
A series of logical steps to follow in order to
solve problems.
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OBSERVE
FORMULATE A QUESTION
FORM A HYPOTHESIS
DESIGN AND CONDUCT AN EXPERIMENT
MAKE OBSERVATIONS
RECORD AND ANALYZE DATA
DRAW CONCLUSIONS
FORMULATE NEW QUESTIONS and
CONTINUE CYCLE
Making Measurements
• Measurements are made in this class using SI
units.
• LENGTH (m): distance between 2 points
• VOLUME (L): space occupied.
• MASS (kg): the amount of matter in an object.
• WEIGHT (N): the force with which gravity pulls on a
quantity of matter.
Precision vs. Accuracy
• Accuracy: the extent to which a
measurement approaches the true
value. (correct value)
• Precision: the degree of exactness of
a measurement. (consistancy)
– A scale may be precise to the nearest
100th of a gram, or +/- 0.01g
increasing precision
Precision vs. Accuracy
increasing accuracy
Density = mass/volume
• Example 1:
– What is the density of water
if a 5 mL sample of water has
a mass of 5 g?
D=m/v
D = (5 g) / (5 mL)
D = 1 g/m L
M
D
V
Density = mass/volume
• Example 2:
– What is the mass of 10 mL of
a liquid that has a density of
3.76 g/mL?
D=m/v
m = Dv
m = (3.76 g/mL)(10 mL)
m = 37.6 g
M
D
V
Coke vs. Diet Coke
• Which is less dense?
• Coke or Diet Coke?
Calculations
• Calculate the density of each:
– A can of Coke has a volume of 355
mL and a mass of 394 g (assuming
that the weight of the aluminum can
is constant)
– A can of Diet Coke has a volume of
355 mL and a mass of 355.1 g
(assuming that the weight of the
aluminum can is constant)
M
D
V
Calculations
• Calculate the density of each:
– A can of Coke has a volume of 355
mL and a mass of 394 g
D=m/v
D=394g/355mL
D= 1.11 g/mL
– A can of Diet Coke has a volume of
355 mL and a mass of 355.1 g
D=m/v
D=355.1g/355mL
D= 1.00g/mL
M
D
V
WHY is Diet Coke less dense?
• Coke has 39 grams of sugar in it to make it sweet
(355 + 39g = 394 g)
• Diet Coke only needs .1 gram of Nutra Sweet to
make is as sweet as Coke (355 + .1g = 350.1 g)
• There is less mass in the same volume (355 mL)
Compare Densities to water?
• Water has a Density of 1g / mL
• Coke has a Density of
» 1.11 g/mL
• Diet Coke has a Density of
» 1.00 g/mL
• What happens when Coke and Diet Coke are put in
water?
Make a prediction…
• Coke sinks (more dense) & Diet does not sink
Temperature Conversions
• Temperature is a measure of the average
kinetic energy in a system.
• K = Kelvin
• oF = degree Fahrenheit
• oC = degree Celsius
Temperature Conversions
• K = oC + 273
• oF = (1.8 x oC) + 32
• oC = (oF – 32) / 1.8
Percentage Error
• Calculate this value in labs where the
accepted value is given.
accepted value  measured value
% error 
100
accepted value
Organizing Data
Data is organized and presented in tables, charts, and graphs.
Graph - visual representation of data
1) title
2) x and y axis labeled
3) units for both the x and y axis
4) scale is evenly and correctly spaced for data
5) legend when appropriate
Temperature Increase of a Beaker of Water
Temperature (K)
450
400
350
300
250
0
50
100
150
200
250
300
350
Time (sec)
LINE GRAPH: best for displaying
data that change.
– Independent Variable: x-axis
– Dependent variable: y-axis
400
Number of Death's per 100,000
People
Leading Causes of Death in 2000
350
300
300
233
250
200
150
107
98
100
57
50
0
Heart
Disease
Cancer
Diabetes
Accidents
Homicide
BAR GRAPH: useful when you want to compare
data for several individual items
Favorite Television Shows among Teens
1%
4%
20%
Friends
45%
Will and Grace
Frasier
Dawson's Creek
Other
30%
PIE CHART: ideal for displaying data that are
parts of a whole.
•Scientific Notation/Powers of 10
•Significant Figures
•Dimensional Analysis (Factor Label Method)
Scientific Notation
Scientist use special notation to express
very large or very small numbers.
Example I: 300,000,000 m/sec can be written as…
3 x 108 m/sec
Example II: 1,007,000,000 sec can be written as…
1.007 x 109 sec
Example III: 0.000 000 000 004 76 m is written as…
4.76 x 10-12 m
Converting Metric Measurements
kids have dropped over dead converting metrics
To convert, move the decimal
place the number of stairs you
step on in the direction you are
traveling OR use dimensional
analysis.
kilo-
103
hecto-
102
deca-
101
Example:
3.75 km = ? mm
? = 3,750,000 mm
basic
unit
1
deci-
10-1
centi-
10-2
milli-
10-3
Powers of Ten
Ten
SIGNIFICANT FIGURES
• Scientists indicate the precision of
measurements by the number of digits they
report = sig. figs.
– 3.52 g is more precise than a value of 3.5 g
You’ll never need to ask this question again.
“Hey Mr. Logan, what do I round this number to?”
Significant Figures
“Which digits are significant?”
• Non-zero digits are always significant.
• Zero Rules
– leading zeros are never counted as significant
003851 has 4 significant digits
– captive zeros (between digits) are significant
2012 has 4 significant digits
– trailing zeros with a decimal are significant
1900 (no decimal) 2 significant digits
16.300 (decimal) has 5 significant digits
REVIEW
Determine how many significant figures are in
each of the following measurements.
1)
2)
3)
4)
5)
6)
0.0034050 L
33.600 m
7500.0 g
47,900 mm
7,000,000,001 miles
8.07 Hz
5
___________
5
___________
___________
5
3
___________
10
___________
___________
3
(the first 3 zeros are PLACE
HOLDERS)
(the last 2 zeros are PLACE
HOLDERS)
More practice…
Round the following measurements off so that
they each contain 3 significant figures.
7) 366.2 L
8) 9,047,022 mg
9) 12.76 g
10) 999.9 J
___________
366 L
9,050,000
mg
___________
___________
12.8 g
1.00 x 103 J
___________
Notice this one must be in scientific
notation to have 3 sig. figs.
Significant Figures in Calculations
When multiplying and dividing,
round to the least number of significant figures
in any of the factors (numbers) in the problem.
Example:
2.30 x 04.32 x 1.09 =
10.83024 which rounds to…
10.8
The answer is expressed as 10.8 or 1.08 x 101
since the lowest sig. figs. In the problem is 3.
Significant Figures in Calculations
When adding and subtracting, round your
answer to the least number of decimal places in
any of the numbers involved in the calculation.
Example:
123.25 + 46.0 + 86.257 =
255.507 which rounds to…
255.5
The answer is expressed as 255.5 since 46.0 has
only one decimal place. (the lowest in the problem)
REVIEW
Perform the prescribed operations. Round your
answers to the proper # of sig. figs.
11) 36.57 m / 3.21 s =
12) 41.376g + 13.3g + 42.9g=
13) 5.67 m x 13.44 m
14) (5.83 m/ 2.67 s) /2.1 s
15) 9.374 V x 6
___________
11.4 m/s
97.6 g
___________
76.2 m2
___________
___________
1.0 m/s2
60 V
___________
From now on, we will round all our answers
to the correct # of significant figures
EXTRA REVIEW
• Using a calculator for EXPONONETS
(EE, EXP or x10x button)
– Example 1:
(5.02 x 10-3) x (6.3369 x 105)
= 3181.1238
*put in correct sig figs
(3 sig figs)
= 3180 or 3.18 x 103
Example 2 (use EE button!)
• (2.99 x 106) x (2.334 x 10-3) =
= 6978.66
3 sig figs
= 6980
DIMENSIONAL ANALYSIS
• How old are you in seconds?
– Go from number of years to number of seconds.
EX: 15 years old  _____ seconds old.
To do this, you need to use CONVERSION FACTORS
(a ratio of equivalent values used to express the same quantity
but using different units)
General Format...
given X
going to
coming from
=
46 years X 365 days X 24 hours X 60 minutes X 60 seconds
1 year
1 day
1 hour
1 minute
46 X 365 X 24 X 60 X 60
1X1X1X1
= 1450656000 seconds
1
You can do it!