Introduction to Science

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Introduction to Science
Science the study of the world around us.
Knowledge of the physical or material world
gained through observation and experimentation.
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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.

3
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!!)

4
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.

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The Scientific MethodA series of logical steps
to follow in order to solve problems.

• 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

6
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.

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Precision vs. Accuracy

• Accuracy the extent to which a measurement
  approaches the true value.
• Precision the degree of exactness of a
  measurement.
• A scale may be precise to the nearest 100th of a
  gram, or /- 0.01g

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Precision vs. Accuracy
increasing precision
increasing accuracy
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Density mass/volume

• Example 1
• What is the density of water if a 5 mL sample of
  water has a mass of 5 g?

M
D
V
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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

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Coke vs. Diet Coke

• Which is less dense? Meaning which will float in
  water?
• Coke or Diet Coke?

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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)

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WHY is Diet Coke less dense?

• There is less mass in the same volume (355 mL)
• Coke has 39 grams of sugar in it to sweeten it
  (355 39 394 g)
• Diet Coke only needs 0.1 g of Nutra Sweet to make
  is just as sweet as Coke
  (355 0.1 355.2 g)

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Temperature Conversions

• Temperature is a measure of the average kinetic
  energy in a system.
• K Kelvin
• oF degree Fahrenheit
• oC degree Celsius

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Temperature Conversions

• K oC 273
• oF (1.8 x oC) 32
• oC (oF 32) / 1.8

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Percentage Error

• Calculate this value in labs where the accepted
  value is given.

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Organizing DataData is organized and presented
in tables, charts, and graphs.
GRAPHING...

• 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

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LINE GRAPH

• LINE GRAPH best for displaying data that change.
• Independent Variable x-axis
• Dependent variable y-axis

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BAR GRAPHS
BAR GRAPH useful when you want to compare data
for several individual items
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PIE CHARTS
PIE CHART ideal for displaying data that are
parts of a whole.
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• Scientific Notation/Powers of 10
• Significant Figures
• Dimensional Analysis (Factor Label Method)

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MATH IS THE LANGUAGE OF CHEMISTRY!!!
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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
• Ex II 1,007,000,000 sec can be written as
• 1.007 x 109 sec
• Ex III 0.000 000 000 004 76 m can be written as
  
• 4.76 x 10-12 m

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Converting Metric Measurements (PART 4 of Things
to Know and Love)
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-
basic unit
101
1
deci-
Example 3.75 km ? mm
10-1
centi-
10-2
milli-
? 3,750,000 mm
10-3
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Video

• Powers of Ten

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SIGNIFICANT FIGURES

• Scientists indicate the precision of measurements
  by the number of digits they report sig. figs.
• A value of 3.52 g is more precise than a value of
  3.5 g
• All known digits plus one estimated digit
• the equipment used for a measurement will
  determine the number of sig. figs.

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Significant Figures

• Atlantic - Pacific Rule
• Decimal Present Count from the Pacific side
• Decimal Absent Count from the Atlantic side
• Start counting at the first non-zero number and
  count until you reach the end of the number
• Ex. I 3.00700
• Decimal Present Pacific (left) 6 sig. figs.
• Ex. II 300,700
• Decimal Absent Atlantic (right) 4 sig. figs.
  (the last 2 zeros are PLACE HOLDERS)

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REVIEW
Determine how many significant figures are in
each of the following measurements.
5 (the first 3 zeros are PLACE HOLDERS)

1. 0.0034050 L ___________
2. 33.600 m ___________
3. 7500.0 g ___________
4. 47,900 mm ___________
5. 7,000,000,001 miles ___________
6. 8.07 Hz ___________

5
5
3 (the last 2 zeros are PLACE HOLDERS)
10
3
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More practice
Round the following measurements off so that they
each contain 3 significant figures.

1. 366.2 L ___________
2. 9,047,022 mg ___________
3. 12.76 g ___________
4. 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.
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Significant Figures in Calculations

• When multiplying and dividing, limit and round
  to the least number of significant figures in any
  of the factors.
• Example
• 23.0 x 432 x 19 188,784 190,000
• The answer is expressed as 190,000 or 1.9 x 105
  since 19 has only two sig. figs.

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Significant Figures in Calculations

• When adding and subtracting, limit and round
  your answer to the least number of decimal places
  in any of the numbers involved in the
  calculation.
• Example
• 123.25 46.0 86.257 255.507 255.5
• The answer is expressed as 255.5 since 46.0 has
  only one decimal place.

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REVIEW
Perform the prescribed operations. Round your
answers to the proper of sig. figs.
11.4 m/s

1. 36.57 m / 3.21 s ___________
2. 41.376g 13.3g 42.9g___________
3. 5.67 m x 13.44 m ___________
4. (5.83 m/ 2.67 s) /2.1 s ___________
5. 9.374 V x 6 ___________

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.
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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

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Example 2 (use EE button!)

• (2.99 x 106) x (2.334 x 10-3)
• 6978.66
• 3 sig figs
• 6980

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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 in different units)

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Given Information NOTETAKERS General Format...
going to
given

X
coming from
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GIVEN INFORMATION

• 1 kildurkin 18 gallons
• 2 farkins 1 kildurkin
• 1 hogshead 63 gallons
• 1 barrel 3.3 bushels
• 1 bushel 8 gallons

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Make a UNIT CONVERSION MAP

• Draw connections between the units in the
  conversion factors
• (as you draw connections, check that conversion
  factor off the list)

Its kind of like a road map
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hogshead
kildurkins
farkins
gallons
barrel
bushel
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Dimensional Analysis
Performing these conversions is a lot like going
on a road trip.
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ROAD TRIP!!!
Lets say you want to travel from Oracle Jct to
Casa Grande...
You must travel through Tucson a two part trip.
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Rule You must stay on the roads REMEMBER SIG
FIGS!!!
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DO NOT GO OFF ROAD! ?
X
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Rule You need a map. Sometimes the map can be
in your head. But, not at first. (show all
work!!)
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Lets calculate

• Convert 14 gallons to kildurkins

46

• Convert 14 barrels to hogshead

47

• Convert 3.00 bushels to farkins

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OKLets talk about making maps and solving
conversion problems. The method we use is called
the Factor-Label method, a.k.a. dimensional
analysis.
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For Example Given 1.0 kildurkin 18
gallons
kildurkins
gallons
This is our map.
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For Example Given 1.0 kildurkin 18
gallons
kildurkins
gallons
How many kildurkins is 14 gallons?
1.0 kildurkins
14 gallons
X
0.78 kildurkins
18 gallons
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Lets expand the map...
Also given 2.0 farkins 1.0 kildurkin
kildurkins
farkins
gallons
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Also given 1.0 hogshead 63 gallons
1.0 barrel 3.3 bushels
hogshead
1.0 bushel 8.0 gallons
kildurkins
farkins
gallons
barrel
bushel
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Now, Lets solve a problem. How many hogsheads are
14 barrels?
Finish Here
hogshead
kildurkins
farkins
3
gallons
2
barrel
bushel
Given Start Here
1
The trip will require 3 transitions
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How many hogsheads are 14 barrels?
hogshead
Given
3
gallons
1.0 hogshead
14 barrels
8.0 gallons
3.3 bushels
X
X
X
63 gallons
1.0 barrel
1.0 bushel
2
5.9 hogsheads
barrel
bushel
1
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Now you try one. How many farkins is
3.00 bushels?
End Here
hogshead
kildurkins
farkins
gallons
Start Here
barrel
bushel
This will require 3 Conversions.
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farkins
bushels
gallons
kildurkins
8.0 gallons
1.0 kildurkin
2.0 farkins
3.00 bushels
X
X
X
1.0 bushel
18 gallons
1.0 kildurkin
2.67 farkins
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Wow! How Cool Is That!
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Handout Fun Factor Label

• Handout
• Piece of lined paper (landscape format)
• Front is web for Distance and back is for Vol.
• Conversion Factors change 10-10 to
  1 x 10-10
• Lets do league ? km ? m ? cm to start
• You finish web, then do 3,6,7,9
• Then do vol. web
• Then finish questions 4, 5, 8, 10
• FINISH FOR HW

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