chapter 1 chemistry and chemicals student
TRANSCRIPT
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General, Organic, and
Biological ChemistryFourth Edition
Karen Timberlake
Welcome to
Chemistry 121
2013 Pearson Education, Inc.
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General, Organic, and
Biological ChemistryFourth Edition
Karen Timberlake
Chapter 1
Chemistry andMeasurements
2013 Pearson Education, Inc.Lectures
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2013 Pearson Education, Inc. Chapter 1, Section 1 3
What is Chemistry?
Chemistry is the study of matter and its composition,
structure,
properties, and
reactions
Chemsitry occurs all around you, for example,
when you
cook food,
add chlorine to your pool,
digest food, and
drop an antacid tablet in a glass of water.
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2013 Pearson Education, Inc. Chapter 1, Section 1 4
Success in Chemistry 121
Regular attendance, active participation in
problem solving
Ask questions early and often!
Seek extra help as needed show up beforeclass, take advantage to tutoring sessions
Follow the suggestions given in chapter one
of the text book, learn how to use the differentfeatures of your text book
4
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Using your textbook
Before reading, review topics in Looking Ahead.
Review Learning Goals at the beginning of each
section. Solve Concept Checks to help you understand
the key ideas in each chapter.
After reading, work through Sample Problems
and try the associated Study Checks. Work the sets ofQuestions and Problems at the
end of each section.
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2013 Pearson Education, Inc. Chapter 1, Section 1 6
Active Learning
Use Active Learning methods to help you learn chemistry.
Read all assigned materials before you attend lectures.
Note questions you have about the reading to discusswith your instructor
Practice problem solving.
Attend the office hours for help.
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Form a Study Plan
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General, Organic, and
Biological ChemistryFourth Edition
Karen Timberlake
Chapter 1
Chemistry and
Measurements
2013 Pearson Education, Inc.
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Sec. 1.3 Measurement in Science
walking 2.1 km to campus,
carrying a backpack with a mass of 12 kg, and
observing when the outside temperature has reached22 oC.
Notice that all measurements have 2 components
A numerical value
A unit written after the numerical value, to indicate thetype of measurement made.
We use measurements in everyday life, such as
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Units of Measurement:
The Metric and SI Systems
The metric system and SI (Systme International)
are used
for length, volume, mass, temperature, and time,
in most of the world, and everywhere by scientists.
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Units in the Metric System
In the metric and SI systems, one unit is used for each
type of measurement.
Measurement Metric Base Unit SI UnitLength meter (m) meter (m)
Volume liter (L) cubic meter (m3)
Mass gram (g) kilogram (kg)
Temperature Celsius (C) Kelvin (K)
Time second (s) second (s)
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Length Measurement
Length
uses the unit meter
(m) in both the metric
and SI systems. uses centimeters (cm)
for smaller units of
length.
The letter c in front ofthe m is called a
metric prefix and
denotes a specific
power of 10
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Converting Between Different Units
of Length -- Inches, Centimeters, and
Meters
Useful relationships between units of length
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Volume Measurement
Volume
is the space occupied by a
substance.
uses the unit liter (L) in themetric system.
uses the unit cubic meter
(m3
) in the SI system. is measured using a
graduated cylinder in units
ofmilliliters (mL).
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Converting between Quarts,
Liters, and Milliliters
Useful relationships between units of volume
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Mass Measurement
The mass of an object is
a measure of the quantity
of material it contains.
measured in grams (g) forsmall masses.
is measured in kilograms
(kg) in the SI system.
The standard kilogram for
the United States is stored at
the National Institute of
Standards and Technology.
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Converting Between Pounds,
Grams, and Kilograms
Useful relationships between units of mass
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Temperature Measurement
measured on the Celsius
(C) scale in the metric
system,
measured on the Kelvin (K)
scale in the SI system, and
18C or 64F on this
thermometer.
Temperature indicates how hot or cold a substance
is, and is
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Section 1.4 Scientific Notation
Scientific Notation
is used to write very large
or very small numbers.
is used to give the widthof a human hair (0.000
008 m) as
8 x 10-6 m.
for a large number suchas 100 000 hairs is written
as
1 x 105 hairs.
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Writing Numbers in Scientific
Notation
A number in scientific notation contains a coefficient
between 1 and 10 and a power of 10 and a unit.
When converting a number from standard notation to
scientific notation, the decimal point is moved until
there is only be one digit to the left of the decimal point
For numbers larger than 1, the power of 10 is positive.
For numbers less than 1, the power of 10 is negative
0.0075 L = 7.5 x 0.001 = 7.5 x 10-3 L
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Some Powers of Ten
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Scientific Notation and
Calculators
You can enter a number in scientific notation on
many calculators using the EE or EXP key.
Use the (+/) key to change the value of theexponent from positive to negative.
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2013 Pearson Education, Inc. Chapter 1, Section 1 23
Scientific Notation and
Calculators
You can enter a number in scientific notation on
many calculators using the EE or EXP key.
Use the (+/) key to change the value of the
exponent from positive to negative.
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2013 Pearson Education, Inc. Chapter 1, Section 1 24
Scientific Notation and
Calculators
When a calculator display appears in scientific notation,
it is shown as a number between 1 and 10 followed by a
space and the power of 10.
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Scientific Notation and
Calculators
To write this number in correct scientific notation, write
the coefficient and use the power of 10 as an exponent.
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Converting Scientific Notation to a
Standard Number
When a number in scientific notation has a positive
power of 10,
move the decimal point to the right for the same
number of places as the power of 10 and
add placeholder zeros to give the additional decimal
places needed.
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2013 Pearson Education, Inc. Chapter 1, Section 1 27
Converting Scientific Notation to a
Standard Number
When a number in scientific notation has a negative
power of 10,
move the decimal point to the left for the same
number of places as the power of 10 and
add placeholder zeros in front of the coefficient as
needed.
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General, Organic, and
Biological ChemistryFourth Edition
Karen Timberlake
1.5
Measured Numbers andSignificant Figures
Chapter 1
Chemistry andMeasurements
2013 Pearson Education, Inc.Lectures
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2013 Pearson Education, Inc. Chapter 1, Section 5 29
Representing Measured Numbers
Measured numbers are numbers obtained by using
measuring devices, such as
a scale or analytical balance,
a graduated cylinder,
a clock or stopwatch, or
a ruler
Section 1.5 Measured Numbers and
Significant Figures
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Writing down measured numbers
Make sure you write down all numbers in the
measurement and include the measurement unit
The number of digits you record will depend on the
sentsitivity of the measuring device being used
For example, on a metric ruler with lines marking
divisions of 0.1cm, write the length to 0.1 cm and
estimate the value of the final number to 0.01 cm by
visual inspection (you can estimate one decimal
place beyond the smallest increments on the
measuring deviceThe length of the
wood shown to
the left would be
written down as
4.55 cm
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2013 Pearson Education, Inc. Chapter 1, Section 5 31
The Concept of Significant Figures
When making a measurement, the number ofdigits written down include all the digits you are
certain of plus the first estimated digit.
A number is a significant figure if it is a nonzero number. (234 g, 3 SF)
a zero between nonzero numbers.
(50071 g, 5 SF)
a zero at the end of a decimal number.(50.00 m, 4 SF)
the coefficient of a number is written in
scientific notation. (2.0 x 103 m, 2 SF)
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The Atlantic-Pacific Rule For Significant Digits
Imagine your number in the middle of thecountry
Pacific Atlantic
If a decimal point is present, start counting
digits from the Pacif ic(left) side of the
number, The first sig fig is the first nonzero digit, then
any digit after that.
e.g. 0.003100 would have 4 sig figs
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2013 Pearson Education, Inc. Chapter 1, Section 1 33
The Atlantic-Pacific Rule For Significant Digits
Imagine your number in the middle of thecountry
Pacific Atlantic
If the decimal point is absent, start counting
digits from the Atlantic (right) side, starting
with the first non-zero digit. The first sig fig isthe first nonzero digit, then any digit after that
e.g. 31,400 ( 3 sig. figs.)
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2013 Pearson Education, Inc. Chapter 1, Section 5 34
Scientific Notation and Significant
Zeros
When one or more zeros in a large number are
significant, they are shown more clearly by writing the
number in scientific notation.
5,000. kg 5.000 x 103 kg
If zeros are not significant, we use only the nonzero
numbers in the coefficient.
5,000 kg 5 x 103 kg
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2013 Pearson Education, Inc. Chapter 1, Section 5 35
Exact Numbers
Exact numbers are
those numbers obtained by counting items.
those numbers in a definition comparing two units
in the same measuring system. not measured and do not affect the number of
significant figures in a calculated answer.
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General, Organic, and
Biological ChemistryFourth Edition
Karen Timberlake
1.6
Significant Figures inCalculations
Chapter 1
Chemistry andMeasurements
2013 Pearson Education, Inc.Lectures
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2013 Pearson Education, Inc. Chapter 1, Section 6 37
Sec. 1.6 Mathematical Calculations
and Significant Figures
The number of significant
figures in measured
numbers are used to limit
the number of significant
figures in the final answer.
Calculators do not provide
the appropriate number of
significant figures.
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2013 Pearson Education, Inc. Chapter 1, Section 6 38
Rounding Off
To represent the appropriate number of significant
figures, we use "rules for rounding."
1. If the first digit to be dropped is 4 or less, then it, and
all following digits are simply dropped from thenumber.
2. If the first digit to be dropped is 5or greater, then the
last retained digit of the number is increased by 1.
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Rounding Off
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When multiplying or dividing use
the same number of significant figures (SF) as the
measurement with the fewest significant figures, and
the rounding rules to obtain the correct number ofsignificant figures.
Multiplication and Division
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When multiplying or dividing use
the same number of significant figures (SF) as the
measurement with the fewest significant figures, and
the rounding rules to obtain the correct number ofsignificant figures.
Multiplication and Division
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2013 Pearson Education, Inc. Chapter 1, Section 5 42
Sometimes we add one or more significant zeros to
the calculator display in order to obtain the correct
number of significant figures needed.
Example:
Suppose the calculator display is 4, and you need
3 significant figures.
4 becomes 4.00
1 SF 3 SF
Adding Significant Zeros
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2013 Pearson Education, Inc. Chapter 1, Section 5 43
When adding or subtracting, use
the same number of decimal places as the
measurement with the fewest decimal places and
the rounding rules to adjust the number of digits inthe answer.
one decimal place
two decimal places
calculated answerfinal answer (with one
decimal place)
Addition and Subtraction
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2013 Pearson Education, Inc. Chapter 1, Section 5 44
Sec. 1.7 Metric Prefixes and Equalities
A prefix in front of a unit increases or decreases the size of that
unit.
makes units larger or smaller than the initial unit by one
or more factors of 10. indicates a numerical value.
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Metric and SI Prefixes
Prefixes that increase the size of the unit:
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Metric and SI Prefixes
Prefixes that decrease the size of the unit:
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Daily Values for Selected Nutrients
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An equality
states the same measurement in two different units.
can be written using the relationships between two
metric units.
Example: 1 meter is the same as 100 cm and 1000 mm.
Metric Equalities
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Measuring Length
The metric length of 1 meter is the same length as 10 dm, 100 cm,
and 1000 mm.
Q How many millimeters (mm) are in 1 centimeter (cm)?
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Measuring Volume
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Measuring Mass
Several equalities can be written for mass in
the metric (SI) system.
S 1 8 S l i P bl I Ch it
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Sec. 1.8 Solving Problems In Chemsitry
Using Dimensional Analysis and Conversion
Factors Dimensional Analysis is a problem-solving
method used in science
It depends on your ability to identify the
numerical information given by the problem,
and your ability to identify the numerical
information you are supposed to find when
solving the problem. The link between the known value (given)
and the unkown value (find) is called a
Converion Factor
52
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Equalities
use two different units to describe the same measured
amount.
are written for relationships between units of the metric
system; between U.S. units or between metric and
U.S. units.
Examples:
Equalities
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2013 Pearson Education, Inc. Chapter 1, Section 8 54
Equalities are
written as a fraction.
used as conversion factors.
can be represented with one equality in the numeratorand the second equality in the denominator.
Examples:
Equalities and Conversion Factors
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Common Equalities
E t d M d N b
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Exact and Measured Numbers
in Equalities
Equalities between units of
the same system are definitions with numbers that
are exact.
differentsystems (metric and U.S.) are
measurements with numbers that have significant
figures.
The equality of 2.54 cm = 1 in. is an exception and
considered to be exact.
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Metric Conversion Factors
We can write equalities as conversion factors.
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2013 Pearson Education, Inc. Chapter 1, Section 8 58
MetricUS conversion factors are written as a ratio with
a numerator and denominator.
Example:
Metric-US Conversion Factors
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2013 Pearson Education, Inc. Chapter 1, Section 8 59
Equalities on Food Labels
The contents of packaged foods
in the U.S. are listed in both metric and U.S. units.
indicate the same amount of a substance in two
different units.
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A percent factor
uses a ratio of the parts to the whole in a fraction.
uses the same units for the parts and whole.
uses the value 100 for the whole.
can be written as two factors.
Example:A food contains 18% (by mass) fat.
Percent as a Conversion Factor
G l O i d
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General, Organic, and
Biological ChemistryFourth Edition
Karen Timberlake
1.9
Problem Solving
Chapter 1
Chemistry andMeasurements
2013 Pearson Education, Inc.Lectures
Guide to Problem Solving Using
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There are 4 steps to solving problems with conversion
factors.
Guide to Problem Solving Using
Conversion Factors
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If a person weighs 164 lb, what is the body mass inkilograms?
Step 1 State the given and needed quantities.Analyze the Problem
Step 2 Write a plan to convert the given unit to the
needed unit.
lb USMetric kilogramsFactor
Steps to Solving the Problem
Given Need
164 lb kilograms
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If a person weighs 164 lb, what is the body mass in
kilograms?
Step 3 State the equalities and conversion
factors.
Step 4 Set up the problem to cancel units and
calculate the answer.
Steps to Solving the Problem
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If a person weighs 164 lb, what is the body mass in
kilograms?
Step 3 State the equalities and conversion
factors.
Step 4 Set up the problem to cancel units and
calculate the answer.
Steps to Solving the Problem
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Often, two or more conversion factors are required to
obtain the unit needed for the answer.
Unit 1 Unit 2 Unit 3
Additional conversion factors are placed in the setup
to cancel each preceding unit.
Using Two or More Factors
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How many minutes are in 1.6 days?
Step 1 State the given and needed quantities.
Analyze the Problem.
Step 2 Write a plan to convert the given unit to the
needed unit.days time time min
factor 1 factor 2
Example: Problem Solving
Given Need
1.6 days minutes
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How many minutes are in 1.6 days?
Step 3 State the equalities and conversion factors.
Step 4 Set up problem to cancel units and
calculate answer.
Example: Problem Solving
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Density
compares the mass of an object to its volume.
is the mass of a substance divided by its volume.
are measured in g/L for gases.
are measured in g/cm3 or g/mL for solids and liquids.
Density expression:
Density
General Organic and
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General, Organic, and
Biological ChemistryFourth Edition
Karen Timberlake
1.10
Density
Chapter 1
Chemistry andMeasurements
2013 Pearson Education, Inc.Lectures
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Density
compares the mass of an object to its volume.
is the mass of a substance divided by its volume.
are measured in g/L for gases.
are measured in g/cm3 or g/mL for solids and liquids.
Density expression:
Density
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Densities of Common Substances
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Density Calculations
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Calculating Density
If a 0.258-g sample of HDL has a volume of 0.215 cm3,
what is the density, in g/cm3, of the HDL sample?
Step 1 State the given and needed quantities.
Analyze the Problem.
Step 2 Write the density expression.
Given Need
0.258 g HDL
0.215 cm3 HDL
density in g/cm3 of HDL
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Calculating Density
If a 0.258-g sample of HDL has a volume of 0.215 cm3
,what is the density, in g/cm3, of the HDL sample?
Step 3 Express mass in grams and volume in
milliliters (mL) or cm3
.
Step 4 Substitute mass and volume into the density
expression and calculate the density.
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Sink or Float
Ice floats in water because the density of ice is less than
the density of water.
Aluminum sinks in water because its density is greater
than the density of water.
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Density can be written as a conversion factor.
Problem Solving using Density
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Density can be used as a conversion factor.
A density of 3.8 g/mL, can be written as an equality,
or written as conversion factors.
Problem Solving using Density
Problem: Density as a Conversion
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Problem: Density as a Conversion
Factor
If the density of milk is 1.04 g/mL, how many grams of
milk are in 0.50 qt of milk?
Step 1 State the given and needed quantities.Analyze the Problem.
Problem: Density as a Conversion
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Problem: Density as a Conversion
Factor
If the density of milk is 1.04 g/mL, how many grams of
milk are in 0.50 qt of milk?
Step 1 State the given and needed quantities.Analyze the Problem.
Problem: Density as a Conversion
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Problem: Density as a Conversion
Factor
If the density of milk is 1.04 g/mL, how many grams of
milk are in 0.50 qt of milk?
Step 2 Write a plan to calculate needed quantity.
volume USMetric density mass
factor factor
Step 3 Write equalities and conversion factors.
Problem: Density as a
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Problem: Density as a
Conversion Factor
If the density of milk is 1.04 g/mL, how many grams of
milk are in 0.50 qt of milk?
Step 4 Set up the problem to calculate the needed
quantity.
S ifi G i
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Specific Gravity (sp gr)
is the relationship between the density of a
substance and the density of water.
is determined by dividing the density of the sample
by the density of water.
is a unitless quantity.
Specific Gravity
S ifi G i
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Specific Gravity is measured by an instrument called
a hydrometer.
Specific Gravity