Analyzing Data

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Transcript Analyzing Data

Analyzing Data
Chapter 2
Units & Measurement – section 1

Chemists use an internationally recognized system of units to communicate
their findings.
SI Units of Measure

All measurements need a number and a ______________.


Example: 5 ft 3 in
or
25ºF
Scientists usually do not use these units. They use a unit of measure called
SI or _____________________________________________.

Base Units – more examples on following slide
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________ - straight line distance between 2 points is the meter (m)
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_________ -quantity of matter in an object or sample is the kilogram
(kg)
The International System of Units
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SI Units of Measure
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Derived Units
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These are units that are made from ________________ of base units.

_____________ -amount of space taken up by an object. l x w x h (m3)
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____________ -ratio of an object’s mass to its volume. D = m/v (kg/m3)
SI Unit of Measure
Metric Prefixes
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0.009 seconds = 9 milliseconds (ms)
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12 km = 12000 meters
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Gigabyte = 1,000,000,000 bytes
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Megapixel = 1,000,000 pixels
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Some common prefixes:
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_______ - 1000
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Hecta- 100
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________ - 10
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(base unit) 1
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_________ - 0.1
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Centi-
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_________ - 0.001
0.01
Nutrition labels often have
some measurements listed in
grams and milligrams
Measuring Temperature

______________ An instrument that measures temperature, or how hot an
object is.
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Fahrenheit scale: water freezes at 32ºF and boils at 212 ºF
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Celsius scale: water freezes at _____ and boils at ______ºC
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ºC = 5 (ºF- 32)
9
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ºF = 9 ºC + 32
5
The SI unit for temperature is the _____________(K)
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0K is the lowest possible temperature that can be reached.
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In ºC, it is -273.15 ºC
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K = ºC + 273
ºC = K – 273
Conversion Factors
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Conversion Factors- Ratio of equivalent measurements that is used to convert
a quantity expressed in one unit to another ____________.
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

Examples:
1 km
or
1000 m
1000 m = 100 Dm = 10 hm = 1 km
1000 m
1 km
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Primary conversion factor:
8848m ( 1km ) = 8.848 km
1000m
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Secondary conversion factor:
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12 km (1000m) (1000mm) = 1.2 x 107 mm or 12,000,000 mm
1km


1m
Tertiary conversion factor:
5 km (1000m) ( 1hr ) = 1.39 m/sec
1 hr 1 km
3600sec
REVIEW Units & Measurement
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What are the SI base units for time, length, mass, and temperature?

How does adding a prefix change a unit?
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How are the derived units different for volume and density?
REVIEW Units & Measurement - Vocab
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Base unit –

Second –

Meter –
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Kilogram –
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Kelvin –
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Derived unit –
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Liter –
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Density -
Scientific Notation – section 2

Scientists use scientific methods to systematically pose and test solutions to
questions and assess the results of the tests.
Scientific Notation
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_________Notation – They way we are use to
seeing numbers.

Example:
Three hundred million = 300,000,000
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__________Notation – A way of expressing a
value as the product of a number between 1
and 10 and a power of 10.
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Example:
300,000,000 = 3.0 x 108


The exponent 8 tells you the decimal point is
really eight places to the right of 3.
Example:
0.00086 = 8.6 x 10-4
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The exponent -4 tells you the decimal point is
really four places to the left of 8
Scientists estimate that there are more
than 200 billion stars in the Milky Way
galaxy.
Scientific Notation

Adding & subtracting
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To add and subtract numbers they MUST have the same ________,
if they do not you need to write in standard notation and then put
back to scientific notation
Example: 8.6 x 10-4 + 6 x 10-4
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& 8.6 x 10-4 + 6 x 10-5
Multiplying & dividing

To multiply, 1st multiple the coefficients then _____the exponents.
Example: 8 x 10-4 X 6 x 10-4
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To divide, 1st divide the coefficients then ________the exponents.
Example: 8 x 10-4 / 6 x 10-5
Math Practice
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
Perform the following calculations. Express your answers in scientific notation.
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(7.6 × 10−4 m) × (1.5 × 107 m)
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0.00053 ÷ 29
2.Calculate how far light travels in 8.64 × 104 seconds. (Hint: The speed of light is about
3.0 × 108 m/s.)1.Perform the following calculations. Express your answers in scientific
notation.
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(7.6 × 10−4 m) × (1.5 × 107 m)
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0.00053 ÷ 29
REVIEW Scientific Notation
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Why use scientific notation to express numbers?
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How is dimensional analysis used for unit conversion?
REVIEW Scientific Notation - Vocab
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scientific notation –
Uncertainty & Representing Data –
section 3 & 4
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Measurements contain uncertainties that affect how a calculated result is
presented.
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Graphs visually depict data, making it easier to see patterns and trends.
Limits of Measurement
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_____________A gauge of how exact a measurement is
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Significant figures- all the digits that are known in a
measurement, plus the
last digit is estimated. 5.25 minutes has 3 significant figures. 5 minutes has 1
significant figure.
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The fewer the significant figures, the less precise the
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The precision of a calculated answer is limited by the least precise measurement
used in the calculation.

Example: Density = 34.73g
= 7.857466 g/cm3
4.42cm3
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You must round to 3 significant figures: 7.86 g/cm3
measurement is.
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________Closeness of a measurement to the actual value of what is being
measured.
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Example: A clock running fast will be precise to the nearest second, but it
won’t be accurate, or close to the correct time.
A more precise
time can be
read from the
digital clock
than can be
read from the
analog clock.
The digital clock
is precise to the
nearest second,
while the analog
clock is precise
to the nearest
minute.
Accuracy vs Precision
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Accuracy refers to how close a
measured value is to an accepted
value.
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Precision refers to how close a
series of measurements are to one
another.
Error

_____________is defined as the difference between an experimental value and
an accepted value.
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a: These trial values are the most precise
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b: This average is the most accurate
% Error
The error equation is
error = experimental value – accepted value.
________________ expresses error as a percentage of the accepted value.
Example: You conducted an experiment and concluded that 84 pineapples would
ripen but only 67 did. What was your % error?
Significant Figures
Often, precision is limited by the tools available. Significant figures include all
known digits plus one estimated digit.
Sig Fig Rules
Significant Figures
Rules for significant figures:
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Rule 1: _________________numbers are always significant.
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Rule 2: __________between nonzero numbers are always significant.
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Rule 3: All final zeros to the right of the decimal are significant.
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Rule 4: Placeholder zeros are not significant. To remove placeholder zeros,
rewrite the number in scientific notation.
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Rule 5: Counting numbers and defined constants have an ________number of
significant figures.
Sig Fig Practice
Rounding
Rounding Numbers
Calculators are not aware of significant figures. Answers should not have more significant
figures than the original data with the fewest figures, and should be rounded. Rules for
rounding:
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Rule 1: If the digit to the right of the last significant figure is less than 5, do not change
the last significant figure. 2.532 → 2.53
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Rule 2: If the digit to the right of the last significant figure is greater than 5, round up the
last significant figure. 2.536 → 2.54
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Rule 3: If the digits to the right of the last significant figure are a 5 followed by a nonzero
digit, round up the last significant figure. 2.5351 → 2.54
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Rule 4: If the digits to the right of the last significant figure are a 5 followed by a 0 or no
other number at all, look at the last significant figure. If it is odd, round it up; if it is even,
do not round up. 2.5350 → 2.54
2.5250 → 2.52
Rounding
Rounding Numbers
______________________________________

Round the answer to the same number of decimal places as the original
measurement with the fewest decimal places.
____________________________________
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Round the answer to the same number of significant figures as the original
measurement with the fewest significant figures.
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Organizing Data
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Scientists can organize their data by using data
tables and graphs
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Data table- the simplest way to organize data. The
table shows two variables - a ______________variable
and the ________________variable.
 Line
graph

Line graphs are useful for showing changes that occur in related variables. It shows
the manipulated variable on the x-axis and the responding variable on the y-axis.
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Slope- (steepness) The ratio of a vertical change to the corresponding horizontal
change.
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Slope = Rise
Run
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Rise represents the change in the _______________________
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Run represents the corresponding change in the ____________________
________proportionRelationship in which the
ratio of the two variables is
constant.
________proportionRelationship in which the
product of the two
variables is constant.

______ graphs and ______ or circle graphs can also be used to display
data.
REVIEW Uncertainty & Representing
Data

How do accuracy and precision compare?
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How can the accuracy of data be described using error and percent error?
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What are the rules for significant figures and how can they be used to express uncertainty in
measured and calculated values?
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Why are graphs created?
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How can graphs be interpreted?
REVIEW Uncertainty & Representing
Data - Vocab
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Accuracy –
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Precision –
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Error –
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percent error –
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significant figure –
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Graph -