Chemistry & Measurement

Get Hand Outs—next 2 projector
Mini Quiz #1
• What are four materials that you will need
for this class?
September 2nd, 2009
It is time to take some notes…
Chemistry & Measurement
• Chemists use tools like
pipettes to accurately
measure liquids.
• Some pipettes can be used to
accurately measure liquids to
tenths, even hundredths of a
• Careful measurement is vital
in scientific investigations.
• In Unit 1 you will learn about
the nature of science and…
• You will also learn how
scientists make and record
Nature of
Certainty &
Units &
Big Goals for Learning
• To describe science and the scientific method.
• To compare qualitative and quantitative
• The express numbers in scientific notation
• To express accuracy, precision and certainty
• To use the rules for significant figures in
• To use metric prefixes and conversion factors
• To work with units of density and other derived
• define chemistry
• identify qualitative and quantitative
• list the main steps in the scientific method
• describe the nature of science
Key Terms
Chemistry & the Nature of Science
• Science is a system of knowledge
about the natural world.
• It is also a way of improving and
increasing that knowledge.
• Latin “scientia” means “to have
• Chemistry is one field of science
along with field of biology,
astronomy, zoology, ecology, etc.
Chemistry & the Nature of Science
• Chemistry is the study of matter and how
it changes.
• Matter is anything that has mass and
• Mass is a measure of how much matter an
object contains.
• Volume is the amount of space and object
takes up.
• Matter is all around you…
• The air you breathe, the juice you had for
breakfast and you, to name a few.
Chemistry & the Nature of Science
• Chemists are scientists who study
matter and its changes.
• They do so with two different types
of observations.
• Qualitatively, they look and the
object; its shape, color, hardness,
viscosity, odor, etc.
• Quantitatively, they take
measurements of the substance to
determine its volume, temperature,
mass, etc.
Chemistry & the Nature of Science
• Besides studying the characteristics
of a substance, chemists want to
know how the substance changes.
• Does it react, or combine with, other
• How is it that hydrogen gas combines
with oxygen gas to make liquid
• This is the beginning of what
chemists do…question their
Rules of the Lab
• Use an indoor voice only to the people in your lab
group. Do not wander from table to table.
• There is no unauthorized work in the lab.
• Use the equipment according to instructions.
• Wear protective clothing such as a lab apron. Always
wear shoes in the lab. Chemical splash goggles are
required when you are working in the lab.
• Avoid loose clothing or dangling jewelry; tie back long
hair when an open flame is in use.
• Always dispose of chemicals in the specified manner.
Do not use the drain indiscriminately.
• Treat the lab with respect.
Mini Quiz #2
1. Name the lab equipment quiz...
2. After the Mini Quiz  Get into lab
groups and select a leader ASAP...the
leader needs to come see Mr. Holt as
soon as he/she is elected.
Into the Lab we Go!
• In your group, you need to elect a leader,
reader, artist, labeler.
• The leader is to make the lab run smoothly,
• know what is going on and keep everyone
on task.
• If anyone in the group is slacking, it is the
leader’s job to get them back on task.
• Ultimately if the team fails, the leader fails.
• Only the leader may speak with Mr. Holt.
Into the Lab we Go!
• The reader’s job is to read the
question to the group.
• They are also supposed to read the
index cards throughout the room to the
• The reader may not speak with Mr.
Holt at any time during the lab 
Into the Lab we Go!
• The artist’s job is to design the blueprint for
the poster board.
• They may ask the group for ideas but they
are not required to.
• The leader may force the artist to work with
the group.
• The artist may not speak with Mr. Holt at
any time during the lab 
• As you travel from station to station, it is
the artist’s job to make sure everyone
understands each index card.
Into the Lab we Go!
• The labeler’s job is to come up with the
“balloons” of descriptions on the poster board.
• They may ask the group for ideas but they are
not required to.
• The leader may force the labeler to work with
the group.
• The labeler may not speak with Mr. Holt at any
time during the lab 
• The labeler must design a name sheet for the
group with a team name, team members and a
• The labeler must carry this around with the
Into the Lab we Go!
• The goal of the lab group is to divide
up tasks, but work as a team.
• Every member of the group must
answer the questions of the handout
and they must be able to answer any
questions Holt may have about the lab
or lab equipment.
• The only time a group member other
than the leader can speak to Mr. Holt
is if he asks you a question.
More Key Terms
Scientific method—
Independent variable—
Dependent variable—
The Scientific Method
• Science is a system of knowledge.
• It is based on observations about the
natural world. But it is more than
• It is also a process of learning about
the natural world.
• Scientists use a process called the
scientific method to answer
questions or solve problems.
• They try to explain why matter
behaves like it does.
The Scientific Method
• The scientific method is a way of
improving and increasing existing
knowledge based on existing facts
and ideas, new observations and
reason or logic.
The Scientific Method
• The process can vary quite a bit but
it often involves the following steps:
• Observe the natural world.
• Ask a question or state a problem
based on observations.
• State a hypothesis based on facts—a
hypothesis is a possible explanation
based on facts and reason. It
predicts what might happen.
The Scientific Method
• Test the hypothesis by designing and
performing experiments.
• The qualitative and quantitative
observations made during
experiments are called data or
• Analyze the results.
• This means organizing the data,
looking for patterns and making sense
of the data.
The Scientific Method
• Share the results and conclusions with
others stating whether the experimental
data supported the hypothesis or not.
• If not, what things might you add or change
in the experiment or hypothesis to bring us
closer to truth.
• Scientists share their findings in published
journals so that scientist all over the world
can read and reproduce their experiments
comparing results and checking for errors.
• In many experiments, certain conditions
or characteristics of matter are
measured or controlled.
• These are variables.
• Variables may change during an
experiment or they may be held constant.
• Volume, temperature, type of substance
and time are all variables.
Mini Quiz #3 (9/8/09)
• Get hand out of HW problems...
• Then for our the piece of
glassware...from this site:
• Copy down my blog site...there will be
info placed here throughout the year.
• Some experiments are designed to see
how one variable changes when another
variable is changed.
• The variable that is changed by the
experimenter is the independent variable.
• The other variable is the dependent
variable—it responds to the independent
Under lamp for
1 hour
Under lamp for
2 hours
Under lamp for
3 hours
After the time goes by the chemist measures the volume of water that
remains after evaporation…
Independent variable = time, dependent variable = volume of water that
evaporates due to the changing time under the heat lamps
Which is Which?
• A chemistry student is trying to determine
what factor will make 2.0g of salt crystals
dissolve the quickest. He tells you that his
teacher gave him a poor grade on his set up.
He tells you his set up and it is your job to
help him fix it. This is what he did...
• He took 2.0g of salt crystals and put them
into 100mL of 30ºC water and let it dissolve.
He recorded the time that it took to dissolve
all the crystals. Then he took 2.0g of salt
crystals and put them into 500mL of 80ºC water
and stirred the solution.
• What would you suggest...write up your plan.
Which is Which?
• Possible set up...
• Get three beakers of 200mL of distilled water—
two beakers at 30ºC and the 3rd at 80ºC.
• Into the first beaker dump 2.0g of salt
crystals in and record the time to dissolve.
This is the control and all the other tests
should be based around this one.
• To the 2nd beaker...add the 2.0g of salt and
stir it with a spoon until all the salt has
dissolved. Record the time.
• Then to the 3rd beaker...add the 2.0g of salt
and do not stir—let the salt dissolve and
record the time.
Which is Which?
• The independent variable is the variable that
the chemist changes. In test #2, what is the
independent variable?
• The dependent variable is the variable that
changes because the chemist change something
from the control. What is the dependent
variable in the 2nd test?
• What is the independent variable in the 3rd
• What is the dependent variable in the 3rd test?
• One way to analyze the results of an
experiment is to make a graph.
• The relationship between the two
variables can be seen on the graph.
• The independent variable is plotted on
the x-axis and the dependent variable on
the y-axis.
Other Stuff to Know
• Experiments cannot prove that a hypothesis is
• However, scientists perform the experiments
many times.
• Each time new results support the hypothesis,
the hypothesis become more likely.
• If the results of many experiments support
the hypothesis, scientists may call this
hypothesis a theory.
• A theory is a well-tested hypothesis that is
widely accepted.
Other Stuff to Know
• An example is the atomic theory of
• It explains matter in terms of atoms and
the tiny particles that make up atoms:
protons, neutrons and electrons.
• Many experiments have supported the
idea that matter is made of these tiny
The Science of Nature
• People of all cultures have been observing and
studying the world for many centuries.
• Because of this, the body of scientific
knowledge continues to grow and change.
• A new discovery may change an existing theory.
• New results may give meaning to old
• New tools may measure or show something for
the first time.
• As the process of science answers one
question, it leads to many new questions.
The Science of Nature
• When scientific knowledge is used in a
practical way to improve lives, the result
is called technology.
• For example, if a chemist comes up with a
drug that slows a human disease, that
development is called technology.
• Scientists generally do not focus on ways
to apply what they learn.
• Instead, engineers apply scientific
knowledge and create technology.
Mini Quiz #4 (09/09/09)
• List and identify all of the qualitative (QL)
and quantitative (QT) observations…
• On the 3rd day of September I was
working in the lab with 5.0g of a white,
crystalline solid. My teacher asked me to
place it in 250mL of a clear liquid with no
odor. I measured and recorded the mass
of the liquid to be 250g. When I placed
the solid in the liquid I noticed that the
solid dissolved. When I placed the beaker
on the scale it now read 255.0 g.
• Write a number in scientific notation
• Convert a number in scientific notation to standard
• Give examples of accurate measurements and
precise measurements
• Know how the quality of a measuring tool affects
• Identify the significant figures in a measured
Key Terms
Scientific notation—
Significant figure—
Scientific Notation
• Scientists often have to measure very large
amounts or very small amounts.
• To make it easier to work with, they write numbers
in scientific notation.
• Scientific notation is a shortcut that uses powers
of 10.
• Powers of 10 are written as 10x, where x is a
number called and exponent.
• The exponent is shown as a superscript, a number
written just above the writing line.
• The exponent tells how many times 10 is multiplied
by itself. (103 = 10 x 10 x 10 = 1000)
Scientific Notation
• There is an easy way to express a number
in scientific notation.
• Just move the decimal point in the given
number to create a number that is
between 1 and 10.
• For example 3,470,000 the decimal is
moved from behind the last zero to be in
between the 3 and the 3 to get 3.47.
Scientific Notation
• Another…0.00000567 the decimal is moved to go in
between the 5 and the 6 to make 5.67.
• Next count the number of places you moved the
decimal point and that is your power of 10…
• Example 1, the decimal was moved 6 places and
example 2, the decimal was moved 6 placed.
• When the number greater than 1, the exponent is
positive, when it is less than 1 the exponent is
negative. So…
• Example 1 = 3.47 x 106
• Example 2 = 5.67 x 10-6
• Write the number 765,000,000,000 in
scientific notation.
• 7.65
• Moved the decimal 11 places
• Number is greater than 1 so…
• 7.65 x 1011
• Try 0.000000349
• 3.49 x 10-7
• Write 3.2 x 10-4 in standard notation
• 0.00032
• Give examples of accurate
measurements & precise measurements
• Know how the quality of a measuring tool
affects certainty
• Identify the significant figures in a
measured value
Key Terms
• Accuracy—
• Precision—
• Significant figure—
Accuracy, Precision and Certainty
• Are some measurements better than
• Do measuring tools affect measurement?
• Does it matter how measurements are
written down?
Accuracy, Precision and Certainty
• In science it is important to make
measurements that are both accurate
and precise.
• Accuracy is how close a measurement is
to the correct or accepted value.
• Precision is how close a measurement is
to other measurements of the same
Accuracy, Precision and Certainty
• Dart board analogy of accuracy and
Accuracy, Precision and Certainty
• Scientists work carefully to obtain accurate and
precise measurements.
• Scientists also need to know how certain their
measurements are.
• After measuring something, scientists record the
measurement as a number.
• In any number that represents a measurement,
there are digits that are certain and one digit that
is uncertain.
• The last digit on the right in the number is an
estimate, or best guess.
• This digit is the uncertain one.
Accuracy, Precision and Certainty
• Imagine stepping a scale and it reads 125
• The 5 (furthest number to the right) is an
uncertain measurement.
• If you used a better quality scale it might read
124.8 pounds.
• In this case the uncertain digit would be the 8.
• The value of 124.8 pounds has greater
certainty than 125 pounds so the better quality
scale is gives the more certain measurement.
• The certainty of measurement depends on the
tool that is used.
Accuracy, Precision and Certainty
• Which ruler will give a more certain
1 cm
1 cm
2 cm
2 cm
3 cm
3 cm
Significant Figures
• It is important that scientists correctly
record the certainty of their
• For any measurement value, scientists
only record all of the certain digits plus
one uncertain, or estimated, digit.
• The uncertain digit is the last one on the
• Together there are the meaningful digits
or significant digits.
Significant Figures
124.8 pounds
3 certain digits
1 uncertain digit
4 significant digits total
Example 1: A scientist records a measurement of
6.2345 meters. All of the digits are significant.
Which digits are uncertain?
• Read: The number is 6.2345 is a
measured value that has 5 significant
• Plan: The significant digits in a measured
value always include one uncertain digit at
the far right.
• Solve: In the number 6.2345m the 6, 2,
3, 4 are certain. The 5 is uncertain.
• Reflect: every measured value contains
one uncertain digit. The rest are certain.
• Practice: A scientist records a
measurement of 57 seconds. Both digits
are significant. Which one is uncertain?
• Answer: The 7.
Significant Figures
• Scientists use the following set of rules for
counting the significant digits in a
• Rule 1—Nonzero digits are significant.
• Rule 2—Final zeros to the right of the decimal
point are significant.
• Rule 3—Zeros between two significant digits
are significant.
• Rule 4—Zeros used for spacing the decimal
point are not significant.
• Rule 5—For numbers in scientific notation, all
of the digits before “x10y” are significant.
Significant Figures
Get out the boards, how many sig figs?…
4.44 x 103
Mini Quiz #5 (9/10/09)
Our First Quest will be on Tuesday!
1. Imagine that you are working on an
experiment to determine how reliable your
scale is. Sounds fun, huh? You place a 1kg
mass on the scale and it reads 995g. Is the
scale accurate, precise, both, neither or are
you unsure and need to carry out further
testing? If unsure, explain why?
2. How many significant figures in the
a) 21.02
b) 21.00
c) 0.020
d) 500
e) 5.00 x 102
• Give the correct number of significant
figures when multiplying and dividing
• Know the difference between a
measurement, a defined number, and a
counting number
• Give the correct number of significant
figures when adding and subtracting
Solving Problems with Significant
• Many chemistry problems involve
• Measured values are often multiplied of
• Significant figures are important when
solving these problems.
Multiplying and Dividing with
Significant Figures
• Suppose you measure a room and find
that it is 22 feet long and 9 feet wide.
• The length value, 22, has 2 significant
• The width value, 9, has 1 significant
• The area of the room is length x width:
• A = 22 feet x 9 feet = 198 square feet
rounded to 200 square feet
Multiplying and Dividing with
Significant Figures
• Why was the number rounded to 1
significant figure?
• When multiplying or dividing
measurements, the answer must have the
same number of significant figures as the
measurement with the fewest significant
• Often the answer from a calculator has
more figures than allowed by this rule so
the value must be rounded.
Multiplying and Dividing with
Significant Figures
2.86ft x 1.824ft =
21mi / 8h =
2.625 mi/h
3 mi/h
98.0in x 1.22in =
119.56 in2
120. in2
1.20 x 102 in2
Multiplying and Dividing with
Significant Figures
• Sometimes a number in a problem is not a
• It might be a defined number.
• A defined number is part of a definition
and is not measured.
• For example, suppose you measure
something that is 725cm long and you
want this measurement in meters.
Multiplying and Dividing with
Significant Figures
• You find that 100cm = 1m.
• You divide 725cm by 100 to get 7.25m
• Do you write this as 7m because 100 has
only one significant figure?
• No, the number 100 is part of a
definition and defined numbers do not
limit the significant figures in an answer.
Multiplying and Dividing with
Significant Figures
• In another case, a number in a problem
might be a counting number.’
• Say you have a 28-inch sub sandwich and
you want to split it into 5 equal pieces.
• The number 5 is a counting number, not a
• Counting numbers, like defined numbers,
do not limit the number of significant
figures so, report the answer to 2
significant figures, not 1.
Adding and Subtracting with
Significant Figures
• When adding or subtracting
measurements the amount of significant
figures reported in your answer must be
the same number of decimal places as the
least certain measurement (fewest
decimal places).
• 4.271g + 2g + 10.0g = 16.271g = 16g
• Name common base units
• Identify metric prefixes and know how
they change a base unit
• Use conversion factors
Key Terms
Degree Celsius—
Unit Conversion—
Conversion Factor—
Measurement Units and Unit
• An important part of the scientific method is
sharing results with other scientists.
• Results usually include measured values that
have units.
• A unit is a standard amount used for
• There is usually more than one unit for
measuring something.
• Meters, yards and feet are all used for
measuring length.
• Each of these units represents a different
standard distance.
Base Units
• In 1960, scientists around the world agreed
on one system of measurement called the
International System of Measurement or
• This system uses:
meter (m) for length
gram (g) for mass
Liter (L) volume
Kelvin (K) for temperature (ºC is also used)
second (s) for time (min or hr are also used)
Metric Prefixes
• The base units just viewed are sometimes too
big or too small depending on what is being
• You wouldn’t want to measure the area of a
book in meters or the mass of an elephant in
grams so prefixes are used.
• You must know:
• micro- 0.000001 (1 x 10-6)
• milli- 0.001 (1 x 10-3)
• centi- 0.01 (1 x 10-2)
• deci- 0.1 (1 x 10-1)
• kilo- 1000 (1 x 103)
Unit Conversions (Factor Labeling)
All measurements consist of a number and a unit.
Using the correct unit is important.
Without a unit, a measurement has no meaning.
Using a wrong unit can also cause trouble.
There is a big difference between 8s and 8hr.
Unit conversion is the process of changing a
measurement form one unit to another.
• Some conversion factors are 1 pound = 454g, 1 gal =
3.8L, 1km = 0.62mile, 2.54cm = 1 inch
• Examples of factor labeling (unit conversion)…
How many grams are there in 2.2 tons?
There are 2000lb in 1 ton.
There are 454g in 1 lb.
How fast in m/s is 55mi/h?
There is 1609m in 1 mile.
There are 3600s in 1 h?
Chemistry To Do…
1. Get your mini quiz books.
2. Turn in your Poster on the desk in the back of the
room—you may not work on your Poster now—it is
due now.
3. Sit with a smile and get ready for some mini-quiz fun!
Mini Quiz #6 (9/11/09)
1. How many significant figures are in the
following numbers...
• 20.023cm
• 13.0cm
• 0.0210cm
2. Multiply the 3 measurements above and
record with proper significant figures.
3. Add the 3 measurements above and record
with the proper significant figures.
4. Use factor label to convert 1.10 miles to
mm. (5280ft = 1 mile, 12in = 1ft,
2.54cm = 1in, 10mm = 1cm)
Mini Quiz #6 (9/11/09)
1. How many significant figures are in the
following numbers...
• 20.023
• Five
• 13.0
• Three
• 0.0210
• Three
2. Multiply the 3 measurements above and
record with proper significant figures.
• = 5.466279cm3
• = 5.47cm3
Mini Quiz #6 (9/11/09)
3. Add the 3 measurements above and
record with the proper significant
• 33.044cm
• 33.0cm
4. Use factor label to convert 1.10 miles
to mm. (5280ft = 1 mile, 12in = 1ft,
2.54cm = 1in, 10mm = 1cm)
Practice Time
• Give 2 examples of derived units
• Calculate the density of an object
• Calculate the mass (or volume) of an
object, given its density and volume
Key Terms
• Derived unit—
• Density (D)—
Derived Units
• Suppose you measure the length and
width of a room in meters.
• You could multiply these two
measurements to find the area of the
• Because length and width are both
measure in meters, the unit for area is
square meters (m2).
Derived Units
• If you measured the room’s height, you
could determine the volume (length x
width x height) in cubic meters (m3).
• Both m2 and m3 are called derived
units—measurements units created by
multiplying or dividing other units.
• Density is a derived unit where mass is
divided by volume. D = m / V
Derived Units
• Calculate the density of a substance
with a mass of 24.3g and a volume of
32.9mL. Use the correct unit and the
correct number of significant figures in
your answer.
• D = 24.3g / 32.9mL =
0.7386018g/mL = 0.739g/mL
Derived Units
• What is the volume of an object with a
density of 1.25g/mL and a mass of 281g?
• D=m/V
• DV = m
• V=m/D
• V = 281g / 1.25g/mL
• V = 224.8mL = 225 mL
• Fun fact: the density of pure water is 1 g/mL.
• Another Fun Fact is that 1mL = 1cm3 (Know
• Mass divided by volume is called _______.
• The amount of space an object takes up is its
• After a hypothesis has been tested many times, it
may become a(n)__________.
• In a measured value, a zero that is used only to
space the decimal point is not ___________.
• A unit of mass is the _______.
• The __________ of a measurement is how close
the measurement is to the true or accepted value.
• The ____________________ is used by scientists
to answer a question or solve a problem.
• Large and small numbers can be written more
easily using ________________.
• Area is an example of a quantity requiring a(n)
• A unit for volume is the __________.
• A(n) _________ is a possible explanation based on
facts and reason.
• The amount of matter in an object is its ________.
• The substance began to dissolve is an example
of a _____________ description.
• The number 3,337 has ____ significant figures.
• The number 0.00529 is written as ___________
in scientific notation.
• A beaker is 152g. A student measures the mass
of this beaker three times and gets these results:
137g, 136g and 137g. The measurements are
(according to accuracy and precision)
• Multiply these measurements: 0.4330cm x
• Convert 75.3cm to mm.
• Convert 0.186kg to mg.
• A substance has a mass of 257g and a volume of
352mL. Find its density in grams per milliliter.
• A substance has a density of 0.876g/mL and a
volume of 25.6mL. Find its mass in grams.
• Give an example of a number that has one zero
that is significant and one zero that is not.
• Show the steps involved in converting 10L into
mL using factor label.
• A substance has a density of 1.52g/mL and a
mass of 220g. What is its volume in milliliters.
What do you know?
In which of the following pairings of
metric system prefix and power of ten
is the pairing incorrect?
kilo- and 10-3
micro- and 10-6
deci- and 10-1
mega- and 106
What do you know?
Which of the following statements
about the “significance” of zeros in
recorded measurements is incorrect?
leading zeros are never significant
confined zeros are always significant
trailing zeros are never significant
trailing zeros may or may not be
What do you know?
The estimated digit in the
measurement 65,430 seconds is
What do you know?
When rounded to three significant
figures, the number 43,267 becomes
What do you know?
The uncertainty associated with the
measurement 0.3030 lies in the
Tenths place (0.1)
Hundredths place (0.01)
Thousandths place (0.001)
Ten-thousandths place (0.0001)
What do you know?
The number 273.00, when expressed in
scientific notation becomes
2.73 x 10-2
2.7300 x 10-2
2.73 x 102
2.7300 x 102
What do you know?
The calculator answer obtained by
multiplying the measurements 53.534
and 5.00 is 267.67. This answer
is correct as written
should be rounded to 267.7
should be rounded to 268
should be rounded to 270
What do you know?
The calculator answer obtained by
adding the measurements 8.1, 2.19 and
3.123 is 13.413. This answer
a) is correct as written
b) should be rounded to two significant
c) should be rounded to 13.41
d) should be rounded to 13.4
What do you know?
What is the volume, in milliliters, of
50.0g of a liquid if its density is 1.20
32.1 mL
41.7 mL
60.0 mL
75.0 mL
What do you know?
Which of the following statements
concerning the three major temperature
scales is incorrect?
a) Kelvin scale temperatures can never have
negative values.
b) A Celsius degree and a Kelvin are equal in size.
c) The addition of 273 to a Fahrenheit scale
reading will convert it to a Kelvin scale reading.
d) The freezing point of water has a lower
numerical value on the Celsius scale than on the
Fahrenheit scale.
For Today in Chemistry…
• Today is review for our first quest which is
• You do not need your mini quiz books.
• Please get in the following arrangement now…
Only the
can see the
Only the
captain can
speak, unless
Mr. Holt
After each problem, rotate 1 seat in a clockwise fashion…Captain to Solver, Solver
to Writer, Writer to Helper and Helper to Captain.
Practice for Quest
1. A piece of turquoise is a blue-green solid, has a
density of 2.65g/cm3, a mass of 2.5g, and a
length of 2.6cm. Which of these observations
are quantitative and which are qualitative?
2. A marathon runner covers a distance of
40.0km. What is that distance in meters? In
miles? 1 mile = 1609m. 1000m = 1km
Practice for Quest
3. When you heat popcorn, it pops because it
loses water explosively. Assume a kernel of
corn, with a mass of 0.125g, has a mass of only
0.106g after popping. What percent of its mass
did the kernel lose on popping?
4. Popcorn is sold by the pound in the U.S.
Using 0.125g as the average mass of a popcorn
kernel, how many kernels are in a pound of
popcorn? (1 lb = 453.6g)
Practice for Quest
5. A particular paint has a density of 0.914g/cm3.
You need to cover a wall that is 7.6m long and
2.74m high with a paint layer 0.133mm thick.
(a) What volume of paint (in L) is required? (b)
Oh yeah, what is the mass (in g) of the paint
Practice for Quest
6. You and your lab partner are
asked to determine the density
of an aluminum bar. The mass
is known accurately (to four
significant figures). You use a
simple metric ruler to measure
its dimensions, and after
calculating the volume, you
determine the density given in
the table (Method A). Your
partner uses a precision
micrometer to measure the
dimensions and then calculates
the density (Method B).
Method A
Method B
If the accepted value of density
is 2.702 g/cm3, what is the
average accuracy of Method A
and B?
Which method is the most
Practice for Quest
7. What is the sum AND the product 10.26cm and
8. What is the result of the following calculation?
x  (0.0546)(16.0000)
Practice for Quest
9. A mineral oil has a density of 0.875 g/cm3.
Suppose you spread 0.75g of this oil over the
surface of water in a large dish with a diameter
of 21.6cm. How thick is the oil layer? Express
the thickness in centimeters. Always use the
correct significant figures. The area of a circle
is, of course, A = πr2.
Practice for Quest
10. Liquid nitrogen boils at 77K. What is this
temperature in Celsius degrees, when
K = ºC + 273?
11. The density of air at 0ºC is 1.293 x 10-3 g/cm3.
What is the density of air at this temperature in
grams per liter?
12. The density of mercury at 0ºC is 13.595 g/mL,
at 10ºC it is 13.570 g/mL and at 20ºC it is
13.546 g/mL. Estimate the density of mercury
at 30ºC.
Practice for Quest
13. The volume of a cube is 512 cm3. What is the volume
of this cube in cubic meters?
100 cm = 1m
14. Also know
• the difference between matter, mass & volume
• all the glassware ( for review)
• the steps to the scientific method
• control, independent and dependent variables
• scientific notation