CHAPTER 3
SCIENTIFIC
MEASUREMENT
3.1 OBJECTIVES
 Convert measurements to scientific
notation.
 Distinguish among accuracy, precision, and
error of a measurement.
 Determine the number of significant figures
in a measurement and in a calculated
answer.
3.1- Measurements and Their Uncertainty
Using and Expressing
Measurements
 Measurements are fundamental to the
experimental sciences. For that reason, it is
important to be able to make measurements
and to decide whether a measurement is
correct.
 MEASUREMENT is a quantity that has both a
number and a unit.
 KEYWORD- Measurement
The most important thing to
remember is…….
 Chemists are lazy.
 ….like really really lazy
 I’m not kidding, we are super lazy.
This is why we have Scientific
Notation
 Scientific Notation allows a given number to
be written as the product of two numbers.
 For example:
5,674,000,000,000,000,000,000 would be
written as 5.674 x 1021
 KEYWORD- Scientific Notation
Practice Problems
 CONVERT THE FOLLOWING INTO
SCIENTIFIC NOTATION
 1- 3,400
 2- 0.000023
 3- 101,000
 4- 0.010
 5- 45.01
 6- 1,000,000
 7- 0.00671
 8- 4.50
Practice Problems #2
 CONVERT THE FOLLOWING NUMBERS
INTO STANDARD NOTATION
 1- 2.3 x 104
 2- 1.76 x 10-3
 3- 1.901 x 10-7
 4- 8.65 x 10-1
 5- 9.11 x 103
 6- 5.40 x 101
 7- 1.76 x 100
 8- 7.4 x 10-5
Accuracy, Precision, and Error
Putting it into exact terms…
Accuracy is a measure of how close a
measurement comes to the actual or
true value of whatever is measured.
Precision is a measure of how close a
series of measurements are to one
another.
 KEYWORDS- Accuracy and Precision
How do we use these two
measurements?
To evaluate the accuracy of a
measurement, the measured value
must be compared to the correct
value.
To evaluate precision of a
measurement, you must compare the
values of two or more repeated
measurements.
Determining Error
Lets face it, making exact
measurements in lab is difficult. And
since nobody is perfect, except Mr. P,
you’re going to make mistakes.
The important thing is making sure
you calculate how much you messed
up.
How to calculate error…
Accepted value, which is the correct
value based on reliable references.
Experimental value is the value
measured in the lab.
The difference between the accepted
and experimental values is called
error.
KEYWORDS- Accepted Value,
Experimental Value, Error
And now for the best part!!!!
MATH!!!!
………………..yayyy…
Calculating Error and
Percent Error

Significant Figures in
Measurements
 Measurements must always be reported to
the correct number of significant figures
because calculated answers often depend
on the number of significant figures in the
values used in the calculation.
 Significant Figures are measurements which
include all of the digits that are known, plus
a last digit that is estimated.
 KEYWORDS- Significant Figures
Rules for Sig Figs
These rules will be used for the
remainder of the course. You should
make a copy and keep them on hand
whenever math problems are being
solved. The only time you can not use
them to help you is on a test/quiz.
Rule 1
Every nonzero digit in a reported
measurement is assumed to be
significant.
Ex: 24.7 meters, 0.743 meters, 714
meters
All of these examples have three sig
figs.
Rule 2
Zeros appearing between nonzero
digits are significant.
Ex: 7003 meters, 40.79 meters, 1.503
meters
All of these measurements have 4 sig
figs
Rule 3
 Leftmost zeros appearing in front of nonzero
digits are not significant. They act as
placeholders.
 Ex: 0.0071 meters, 0.42 meters, 0.000099
meters
 All of these examples have 2 sig figs
 To help determine sig fig amounts try writing
the numbers in scientific notation.
Rule 4
Zeros at the end of a number and to
the right of a decimal point are always
significant.
Ex: 43.00 meters, 1.010 meters, and
9.000 meters
All of these measurements have 4 sig
figs
Rule 5
 Zeros at the rightmost end of a
measurement that lie to the left of an
understood decimal point are not significant
if they serve as placeholders to show the
magnitude of the number.
 Ex: 300 meters, 7000 meters, 27,210 meters
 The zeros in these numbers are not
significant
Rule 6
 Two situations involve an unlimited number
of sig figs.
 The first is anytime something is counted, as
in counting the number of people in a
classroom.
 The second is for exactly defined quantities,
such as those found within a system of
measurement.
Significant Figures in Calculations
In general, an answer can only be as
accurate, as the least accurate
measurement.
This is reduced into three general
areas, Sig figs in rounding, addition
and subtraction, and multiplication
and division.
Sig Figs in Rounding
When rounding, first determine the
correct number of significant figures.
Then, counting from the left find the
last significant figure.
Next go ONE more digit to the right, if
it is greater than or equal to 5, round
up, if it is less than 5, drop it.
Rounding Example
4,378.93
What is our answer if we only need 5
sig figs?
386.58
What is our answer if we only need 4
sig figs?
Sig Figs in Addition & Subtraction
The answer to an add/sub
problem should be rounded to
the same number of DECIMAL
places as the measurement with
the least number of decimal
places.
Sig Figs in Multiplication &
Division
In Mult/Div problems you need to
round the answer to the same
number of significant figures as
the measurement with the least
number of sig figs.
3.2 OBJECTIVES
List SI units of measurements
and common SI prefixes
Distinguish between the mass
and weight of an object
Convert between Celsius and
Kelvin temperature scales.
3.2 The International System of Units
Measuring With SI Units
For this class, as well as all science
classes, we use a system of
measurements called the
International System of Units
The International System of
Units (SI) is a revised version of
the metric system
KEYWORDS- The International
System of Units
The Basic Units…
Commonly Used Metric Prefixes
Units And Quantities
Length is measured in a unit
known as the meter
A meter is the basic SI unit of
length
KEYWORD-Meter
Units And Quantities
A liter is used when we are
discussing volume.
A liter is the unit for volume
used SI
KEYWORD-Liter
Units And Quantities
The mass of an object is
measured in comparison to a
standard mass of 1 kilogram
(kg).
A Kilogram is the basic SI unit
of mass.
KEYWORD- Kilogram
Mass vs Weight
Mass is the amount of matter
an object contains.
Weight is a force that
measures the pull on a given
mass by gravity.
KEYWORD-Weight
Units And Quantities
Temperature is a measure of
how hot or cold an object is and
the direction of heat transfer.
The Specifics of Temperature
When it comes to temperature the
SI measurements vary between
Celsius and Kelvin
The Celsius Scale sets the freezing
point of water at 0OC and the boiling
point at 100OC
KEYWORD- The Celsius Scale
The Specifics of Temperature
The Kelvin Scale sets its freezing
point of water at 273.15 K, and the
boiling at 373.15 K.
0K on the Kelvin scale is referred to
as Absolute Zero
KEYWORDS- The Kelvin Scale, &
Absolute Zero
Units of Energy
Energy is the capacity to do work
or to produce heat.
The units for energy are the joule
(j) and the calorie (cal).
KEYWORD- Energy
3.4 Objectives
Calculate the density of a
material from experimental
data.
Describe how density varies
with temperature.
Determining Density

Density and Temperature
The density of a substance
generally DECREASES as its
temperature INCREASES. They
are inversely related.