Download Preliminary Unit - Mr. Donohue`s Chemistry

Science Is A Verb Vocabulary
Word
Definition
Analysis
Coefficient
Control
Conversion Factor
The step in the scientific method where data is used to solve a problem.
The number in FRONT of a formula.
The conditions which remain constant during the experiment
A number or ratio (in fraction form) that is used to convert from one unit
type to another. The given units cancel out, leaving the desired target
units.
That which is measured or observed during an experiment.
The variable on the Y-axis that changes as a result of changing the
independent variable.
A relationship where the increase of the independent variable results in
the increase of the dependent variable.
An activity designed to test the specifics of the hypothesis.
A number that expresses a “power”, is written as a superscript.
Extending the graph beyond the data points to predict values beyond that
which was plotted to get desired information.
Information which is provided to you in the form of a number and a unit.
An “if-then-because” statement used to design an experiment to test an
idea.
The variable on the X-axis that the experimenter has control over.
A relationship where the increase of the independent variable results in
the decrease of the dependent variable, or vice versa.
Reading between plotted data points on a graph to get desired
information.
A straight line that best represents the slope of the data being analyzed.
Can be approximated by hand, or done with linear regression methods.
The place to which a measurement was made.
A specific issue that can be resolved through application of the scientific
method.
A series of logical processes designed to solve problems.
The number of digits actually recorded by a measuring device during a
measurement.
The desired result of a mathematical problem, that which you are solving
for.
A symbol which identifies the type of measurement that has been made.
This needs to be placed after every measured number and every
calculated answer.
The value that changes during the experiment
Data
Dependent Variable
Direct Relationship
Experiment
Exponent
Extrapolation
Given
Hypothesis
Independent Variable
Indirect Relationship
Interpolation
Line Of Best Fit
Precision
Problem
Scientific Method
Significant Figures
Target
Unit
Variable
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Regents Chemistry FAQ
MATERIALS NEEDED FOR COURSE
- Notebook (spiral, one-subject will be enough)
- PENCILS, pens
- Pocket folder
- Calculator. Graphing calculators may be banned from the Regents Exam, so have a spare scientific calculator handy.
- Reference Tables (provided)
- One cranial cavity, stuffed full of brains.
Class Guidelines:
Guideline
Consequence For Noncompliance
Be in your seat ready to work when the bell rings. Late without pass: ½ hour teacher detention in Room 231 that
afternoon (2:20 – 2:50)
Cut: Referral to the main office, parent contact
Remain on task for the duration of the period.
Parent contact, detention if assigned work not completed
Respect the right of all students to learn without
Parent contact
distractions or disruptions.
½ hour teacher detention in Room 304 that afternoon (2:20 to
2:40)
Food and drink is prohibited.
If seen, will be confiscated and disposed of.
Hats and portable electronic multimedia and
If seen, will be confiscated and will be turned over to your parents.
communications devices are prohibited (unless
part of a class project presentation).
WHAT TO EXPECT FROM A TYPICAL CLASS PERIOD
When you enter the class, you will be greeted by some form of review, either questioning, a bell-ringer (limited
time to be completed) or a quiz.
At the beginning of each unit, you will receive two packets. The first one contains all of the notes for the unit,
including sample problems, diagrams, the unit’s vocabulary words and a schedule for the unit. The second packet
contains all of the work that you have to do for the unit. As you finish each topic, you will bring the packet to the front
of the room, where it will be checked for correctness. If correct, you will receive point value for the work (usually 10
points) and you may begin the next topic. If incorrect, you will be advised which sections need to be corrected and
assistance in correcting those sections. The entire packet is due, complete, no later than test day. Some
assignments will be due beforehand, but partial credit will be given if they are turned in by test day. This allows you to
work at your own pace, either to stay with the class or work ahead. Assignment correctly completed before being
taught in class will receive +2 bonus points. The video tutorials available through my blog and youtube may be of
assistance for students looking to get ahead.
The material will be presented to you and you will be given examples of problems to solve or phenomena to
explain and apply. Most days, you will be given ample time to complete the assignment in class. Some days,
especially right after a test, you will be asked to complete the first topic, almost always an introductory topic, on your
own for homework. It is highly recommended that you use a PENCIL to complete all assignments.
At the end of the unit you will be given some review, a practice test for example. The day of the test, we will
start by going over the review and then beginning the test.
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IN CLOSING
If asked to refer to a particular reference table, then refer to it. If asked to try solving a problem, then work it
out. Participation is required to successfully complete this course. The grade you get in this class is directly related to
the amount of effort you put into it. Learning isn’t a spectator sport, and if all you do is sit there and watch you won’t get
much out of it. I want you all to do well, and as long as you are working, I can work with you. It is entirely up to you
what kind of grade you want to get. You really do have control over your destiny in this class. Take advantage of that
fact.
Grading Rubric:
Type
Point
Value
Notes
In-Class Worksheets
10-30
You will get an assignment packet at the beginning of every unit. You may work
ahead if you so desire. The packet is due when you take the unit test. No late
packets will be accepted. The packet will be checked on a daily basis to make sure
you are doing your work.
Quizzes
10
You will be given a 5-multiple-choice question quiz at the start and end of EVERY
DAY. 2 points each. In the event of absence, these quizzes must be made up.
Labs
100
1200 minutes of hands-on lab activities are required to sit for the Regents exam.
Projects
100
Given at various times throughout the year.
Tests
100
Given at the end of every unit. Consists of a multiple-choice section and a shortanswer/show-your-work math section. Some tests may forego the multiple-choice
section entirely. Some may be take-home tests which will be due two school days
after being given.
Breakdown Of Grade Percentages For Marking Period Average:
Test and Quizzes
40%
Quarterly
20%
Labs
20%
Class + Homework
20%
Extra Credit: If you complete a day’s assignment correctly before it has been taught, you will get +2 on that page.
Extra Help: Available Tuesdays through Thursdays from 2:20 – 3:10 PM in Room 231. Arrangements for staying later
may be made upon request.
Resources Available To You:
Class Blog: Class Packets, Worksheets and summary of class
activities
www.mrdonohueschem.wordpress.com
Video tutorials that cover every single topic! (Links will also be made
available through the blog)
www.youtube.com/markrosengarten
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Regents Chemistry: TROUBLESHOOTING
PROBLEM
I failed a test.
But I did study and I sill failed!
I think I am going to fail the marking period.
I lost my Reference Tables.
I don't know how to use my calculator.
I didn't bring anything to write with.
I lost the textbook.
Someone in the family died/was in the
hospital/etc. so I couldn't do the homework.
I couldn't do the homework.
I don't have the time to come for help.
I think I am going to fail the Regents exam.
SOLUTIONS
You did not study. Studying does not mean reading your notes.
Studying means DOING. Doing your worksheets over again,
rewriting your notes into another notebook, using flash cards for
vocabulary and other problems are all ways of actively studying.
Studying is not a passive task. A sweat should be broken.
Did you seek extra help the day that you didn't understand
something? When did you start studying? Your homework period
each day should be half studying and half homework. Studying is a
cumulative process, not something you spend an hour on the day
before the test.
Did you do all of your homework? Each homework missed can add
up to a point or more off your marking period average.
Xerox a copy from someone else.
Come in and I will show you how.
Borrow something from someone in the class. I run out writing
implements. If you borrow one, please return it.
It will cost you money to replace it.
Bring in a note from your parents to let me know that this is a
legitimate excuse. Bring homework in next day with the note.
Did you seek extra help?
Make the time. There is always time.
Did you buy a red Barron's book for review? Are you taking all of
the old tests and correcting yourself, checking the explanations for
the ones you got wrong? This process should start at the
beginning of May and go right through to the test.
What is Chemistry?
Chemistry is the study of matter, the changes matter undergoes and the energy involved in these changes. It is the
universe and how it works, the interactions between particles and energy changes.
Syllabus: units to be taught throughout the year
Science Is a Verb
The Atom
Matter and Energy
The Periodic Table
Ionic Bonding
Covalent Bonding
Equations and Mole Math
Phases and Phase Changes
Solutions
Kinetics and Equilibrium
Acids and Bases
Electrochemistry
Organic Chemistry
Nuclear Chemistry
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Tips for Studying Chemistry:
The point is that the most important variable here is
YOUR EFFORT! If your effort is zero, then your
grade will be zero.
· I think it is interesting how “A” students tend to get
those grades, regardless of the teacher. They take
responsibility for their own learning rather than
blaming external factors for their lack of success.
Chemistry is different from any other science course
you have taken:
· The material is new and more abstract, More problem
solving, More math.
Therefore, you need to approach Chemistry with a
more serious attitude and:
1) Be consistent in your study efforts.
2) Practice, practice and practice those homework
problems!
I find that the most common reasons for failure are:
1) Too little study time. We recommend that you study a minimum of 15 minutes per night, for a total of 75 minutes
per week. Reading your notes as a method of study is worse than useless…unless you have a photographic memory.
ACTIVE studying is the only method that really works.
2) Lack of student preparation. Major concern: math skills. You need to be comfortable with numbers and basic
algebra.
3) Lack of consistent effort. Cramming won’t work well. Study regularly and consistently.
4) The wrong approach to studying. Rereading the text and taking notes from the text are not the best way to study.
The most important thing you can do for your learning is to do the homework problems and practice tests.
5) Overconfidence in understanding the material. It is fine to start solving problems with the teacher’s guidance, but
you must put in time at home. On the test, you need to be able to do homework problems without the teacher’s help.
Here are some ideas for ensuring your success in Chemistry:
1) Come to after-school help with specific questions about the course material and homework problems.
2) Rewrite your class-notes and rework through the class exercises.
3) In order to understand a concept rather than simply memorize a definition, try either writing an explanation in your
own words or explaining it to someone else.
4) Study groups can be good because many of us learn by talking and discussing. However, beware that this can be a
timewaster if you tend to drift away from chemistry.
5) Retake old quizzes, old tests and review sheets.
6) Buy the review book and do the problems in there.
7) Distill your notes into graphic organizers such as attribute webs, flow charts and Venn diagrams.
8) Create a “cheat sheet” in which you will have all of the things you need to know for the test.
9) After doing several problems, create new ones to do by taking existing questions and changing the numbers. When
you get good at that, then try creating brand-new problems of your own.
10) Be prepared to do work in class and pay attention to all details being presented. Ask questions when you need to.
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1) Scientific Method
How can problems be solved in a systematic manner?
Scientific Method
You got a problem? YOU GOT A PROBLEM???? Then solve it, using the Scientific Method! It is a logical sequence
of steps designed specifically to solve problems!
Qualities of a ‘good’ experiment Chart
Doctors use the scientific method to diagnose and heal illnesses or injuries.
Politicians use the scientific method to craft their election campaigns.
Arson investigators use the scientific method to determine the cause of fires and determine their point of origin.
Forensic investigators use the scientific method to determine the nature and perpetrators of crime.
Business executives use the scientific method to analyze profit reports and create new business plans.
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While watching the clip from the show Mythbuster, fill in the following chart for their scientific investigation
(http://www.youtube.com/watch?v=WpTSA_25wGE)
Problem
Hypothesis
Experiment
Data
Analysis
Further
Research
Conclusion
Why did they need to do further testing after their first trial?
What was good about their experiment?
How could their experiment be improved?
Adam says: ‘ [I am astonished] that I am finishing the day calling something plausible that I KNEW wasn’t possible
when I woke up this morning’. Do you think there are things that you ‘KNOW’ that just aren’t true?
Question: If a tree starts as a little seed, where does all that ‘stuff’ come from?
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2) Measurement
What is the correct way to measure in science?
It should go without saying, but it is very important for scientific investigations that everyone uses the same
system and measures in the same way for consistency. Numbers tell us more than you might think. After all,
5g is not the same as 5.0g…
Science uses the Metric System
1) Devised in 1960 by the General Conference of Weights and measures
2) Called Le Systeme International d'Unites (SI)
3) Conversions are all in base 10
4) Prefixes used to determine the magnitude of a particular unit (Kilo means 1000, centi means 1/100 th)
METRIC UNITS (Reference Table D)
Symbol
m
G
Pa
K
Mol
J
S
L
Ppm
M
Name
Meter
Gram
Pascal
Kelvin
Mole
Joule
Second
Liter
Parts per million
Molarity
What It Measures
Distance (length, height, width, from here to there)
Mass (how much matter something contains)
Pressure (force exerted over an area)
Temperature (the average kinetic energy of a system)
Amount of substance (6.02 X 1023 things in a mole)
Heat (stored, or potential, energy of a substance)
Time (from one point in time to another)
Volume (cubic length: 1 liter = 1 dm3, 1 milliliter = 1 cm3)
Concentration (mass of solute/mass of solvent X 1000000)
Concentration (moles of solute/L of solution)
METRIC PREFIXES (Reference Table C)
Factor
103 (thousand)
100 (one)
10-1 (tenth)
10-2 (hundredth)
10-3 (thousandth)
10-6 (millionth)
10-9 (billionth)
10-12 (trillionth)
Prefix
KiloDeciCentiMilliMicroNanoPico-
Symbol
k
d
c
m

n
p
Example (Mass)
1 kg = 2.2 pounds
1 g = 0.0353 ounces
1 dg = 0.0000353 ounces
1 cg = 0.00000353 ounces
1 mg = 0.000000353 ounces
1 g = 0.000000000353 ounces
1 ng = 0.000000000000353 ounces
1 pg = 0.000000000000000353 oz.
Example (Distance)
1 km = 0.621 miles
1 m = 3.28 feet
1 dm = 3.94 inches
1 cm = 0.394 inches
1 mm = 0.0394 inches
1 m = 0.0000394 inches
1 nm = 0.0000000394 inches
1 pm = 0.0000000000394 in.
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Math Rules For Chemistry:
1) N3: _______ _______________ _____________________. All measurements and answers to math
problems must have units written after the numbers.
2) ______ _____________, ______ _______________. You must show all of the following when doing math
problems: the equation you are going to use, the equation rearranged algebraically to solve for the variable
you are looking for, the rearranged equation with numbers and units substituted in for all of the variables
(numerical setup) and the final answer, rounded properly with units after.
UNCERTAINTY IN MEASUREMENT
Measurements are made one place beyond where the measuring device is marked. For example, a ruler marked to
the nearest tenth of a centimeter can be read to the hundredths place by estimating how far between the lines the
measurement falls.
This is known as the devices ______________________
------------------------------------cm 1
2
3
4
5
6
7
8
9
Precision:___________
Device is marked to the ONES place, so read to the __________________ place
Measurement: 6.2 cm  the 2 in the tenths place is ESTIMATED
---------------------------cm .1
.2
.3 .4
.5 .6
.7 .8
.9
Device is marked to the TENTHS place, so read to the ________________________ place
Measurement: 0.48 cm  the 8 in the hundredths place is ESTIMATED
DETERMINING PRECISION FROM THE MEASUREMENT:
1) If the measurement has a decimal point in it, the precision is the place furthest to the right in the
measurement.
In the measurement 23.004 cm, there is a decimal point, so the precision of the measurement is the furthest place to
the right, or the thousandths place.
23.004 cm
In the measurement 0.3320 g, there is a decimal point, so the precision of the measurement is the furthest place to the
right, of the ten thousandths place.
0.3320 g
In the measurement 330. mL, there is a decimal point, so the precision of the measurement is the furthest place to the
right, or the ones place.
330. mL
2) If the measurement does not have a decimal point in it, the precision is the place where either the rightmost
integer is, or where a zero with a line over it is.
The measurement 2300 km has no decimal point in it, so the precision is where the rightmost integer is, or the
hundreds place.
2300 km
_
For the measurement 2300 km, there is no decimal point, so the precision is where the zero with the line over it sits, or
the tens place.
_
2300 km
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Significant Figures
What makes a number ‘significant’? A number is significant if it was directly measured or estimated when taking a
measurement. For example:
12000 km: The precision is to the thousands place, therefore the ‘1’ and
‘2’ were directly measured or estimated when this measurement was
taken and are significant. The three ‘0’s were neither measured nor
estimated and are insignificant. This number has _________ SIG FIGS.
0012000 km: This is the same number as before, except there are two
‘0’s in front of it. These ‘0’s were not measured or estimated and are
insignificant. ZERO’s TO THE LEFT OF THE FIRST ‘NUMBER’ ARE
NOT SIGNIFICANT. This number would have __________ SIG FIGS.
12000. km: This is not the same number because of the decimal place.
The decimal place tells us that the precision was to the ones place, so
the ‘0’s in the ones, tens and hundreds places were actually measured
to be zero. This means that the three ‘0’s in the ones, tens and hundreds
places were actually measured to be zero. This makes them significant.
This number would have ___________ SIG FIGS.
In the examples below, the significant figures are underlined and the
precision is in bold.
In the measurement 23.285 cm, the first integer is the 2 in the tens place. The precision of the measurement is the
thousandths place.
23.285 cm  five significant figures.
In the measurement 8000 sec, the first integer is the 8 in the thousands place. The precision is the thousands place.
8000 sec  one significant figure.
In the measurement 40. L, the first integer is the 4 in the tens place. The precision is the ones place.
40. L  2 sig figs
In the measurement 2300 g, the first integer is the 2 in the thousands place. The precision is the hundreds place.
2300 g  two significant figures.
_
In the measurement 2300 g, the first integer is the 2 in the thousands place. The precision is the tens place.
_
2300  three significant figures.
In the measurement 200.0 L. the first integer is the 2 in the hundreds place. The precision of the measurement is the
tenths place.
200.0 L  four significant figures.
In the measurement 0.713 kg, the first integer is the 7 in the tenths place. The precision is the thousandths place.
0.713 kg  three significant figures.
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3) Rounding
How do you round off the answers to math problems?
Addition and Subtraction
The answer can only be as precise as the __________ ________________ of the measurements to be added or
subtracted. The answer must be rounded to the place of precision of the least precise of the measurements. In the
examples, the place of precision is underlined in the measurements.
WHEN ADDING OR SUBTRACTING NUMBERS, RIGHT THERE IN YOUR FACE
LOOK FOR THE ONE THAT’S __________ _____________ AND ROUND IT TO THAT PLACE!
Round the following
number to the
23.337 to the nearest tenth
Rounded answer
Round the following
number to the
10000 to the nearest tenth
23.3
23.337 to the nearest
hundredth
23.337 to the nearest one
Rounded answer
10000.0
10000 to the nearest one
23.34
10000.
_
10000
_
10000
10000 to the nearest ten
23
23.337 to the nearest ten
10000 to the nearest
hundred
20
PLACE CHART
Hundred
Thousands
thousands
decimal
point
tens
ten
thousandths
hundredths
millionths
345678.098765
Ten
Thousands
hundreds
ones
tenths
thousandths
hundred
thousandths
Examples:
a) 33.5 cm
+
7.88 cm
+ 0.977 cm
= 42.357 cm
tenths
hundredths
thousandths
Since TENTHS goes out the least far, round the answer to the nearest TENTH.
ROUNDED = 42.4 cm
b) 23000 km
+
8.7 km
=
23008.7 km
ROUNDED = 23000 km
thousands
tenths
Since THOUSANDS goes out the least far, round the answer to the nearest THOUSAND.
c) 6700 mL
78.7 mL
=
6621.3 mL
ROUNDED = 6600 mL
hundreds
tenths
Since HUNDREDS goes out the least far, round the answer to the nearest HUNDRED.
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IF YOU HAVE SOME MEASUREMENTS TO MULTIPLY OR DIVIDE
ROUND TO THE _____________ SIG FIGS, COUNTING FROM THE LEFTWARDS SIDE!
Multiplication and Division
The answer can contain only as many significant figures as the measurement with the least number of significant
figures. The sig figs in the following measurements are in bold type.
Round the following
number to the
23.337 to 4 sig figs
Rounded answer
Round the following
number to the
10000 to 6 sig figs
23.34
Rounded answer
10000.0
23.337 to 3 sig figs
10000 to 5 sig figs
23.337 to 2 sig figs
10000 to 3 sig figs
23.337 to 1 sig figs
10000 to 1 sig fig
a) 67.23 cm
X
9.22 cm
=
619.584 cm2
ROUNDED = 620. cm2
4 sig figs
3 sig figs
Rounding the answer to 3 sig figs, you need to put the decimal point to show that the 0 is a sig fig.
_
b) 200 cm
X
3.333 cm
=
666.6 cm2
ROUNDED = 670 cm2
2 sig figs
4 sig figs
Rounding to 2 sig figs makes the ones place a place-holding 0 so that the first two integers are the sig figs.
c) 30 g
/
3 mL
=
10 g/mL
ROUNDED = 10 g/mL
1 sig fig
1 sig fig
Sometimes, you don’t need to do anything to your answer. One sig fig is all you need!
d) 30. g
/
3.0 mL
=
10 g/mL
2 sig figs
2 sig figs
To show that 10 has 2 sig figs, put a decimal point after the ones place.
ROUNDED = 10. g/mL
e) 30.0 g
/
3.00 mL
=
10 g/mL
3 sig figs
3 sig figs
To show that 10 has 3 sig figs, take the answer out to the tenths place.
ROUNDED = 10.0 g/mL
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4) Atomic Structure
Essential Question: What is everything made up of?
Atoms are the smallest pieces an element can be broken into and still retain the properties of that element. It comes
from the Greek word atomos, meaning “indivisible” (unbreakable).
Atoms are so tiny that they cannot be seen directly. They can be detected through X-ray crystallography or atomic
force microscopes, but only indirectly.
It takes 602 000 000 000 000 000 000 000 atoms of hydrogen to weigh 1 gram (the mass of a small paper clip).
Atoms are made up of the following particles:
A) Nucleons (____________________________________________________________________)
1) Protons: have a mass of 1 atomic mass unit (1.66 X 10-24 grams) and a charge of +1. They are found in
the nucleus of the atom, and the number of protons in the atom is the atomic number, which identifies what element
the atom is. Oxygen (O) has an atomic number of 8, which means there are 8 protons in the nucleus. Since protons
are the only particle in the nucleus to have a charge, the charge of the nucleus is + (# of protons). Since oxygen has 8
protons in the nucleus, oxygen has a nuclear charge of +8.
2) Neutrons: have a mass of 1 atomic mass unit, and no charge. They are found in the nucleus of the atom,
and the number of neutrons added to the number of protons gives you the mass number of the atom. The number of
neutrons does not affect the identity of the element. Oxygen’s most common form has a mass number of 16. Since
there are 8 protons in the nucleus of oxygen, this means there must also be 8 neutrons to give a combined mass of 16.
The number of protons and neutrons does NOT have to be equal. In addition, atoms of any given element can
have differing numbers of neutrons. Atoms of the same element with different numbers of neutrons in their nuclei are
called ISOTOPES of one another. The most common isotope is the one who’s mass equals the average atomic mass
given on the periodic table rounded to the nearest whole number. Since O has a given average mass of 15.9994, the
most common isotope of O is O-16, or Oxygen with a mass number of 16.
B) Particles Outside The Nucleus
3) Electrons: have a mass of 1/1836 amu (9.11×10−28 grams) and a charge of -1. They are found orbiting the
nucleus in energy levels. Atoms gain, lose or share electrons when they form chemical bonds. The number of
electrons in the atom equals the number of protons. Atoms are neutrally charged, so the + charged protons and the –
charged electrons must be equal in number to give a neutral charge. Oxygen has 8 protons in its nucleus, so there
must be 8 electrons zipping around outside the nucleus in energy levels. In this unit, the only thing you need to worry
about is how to find out how many electrons an atom has, and what the charge and mass of an electron are. Later in
the course, you will see just how important electrons are to all of chemistry. They are the part of the atom responsible
for all chemical bonding. If it weren’t for electrons, there would be no compounds.
Particles at a glance
Protons
Neutrons
Electrons
determines the atomic
_____________/__________,
nuclear charge and contributes
to atomic mass
contributes to atomic
________, number of neutrons
varies depending on the
_____________
Number of electrons
equals number of
____________ for a
neutral atom. React with
other atoms during
reactions.
Significance
Mass (amu)
Charge
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Reading the Periodic Table
1) How many protons does an atom of iron (Fe) have? With an atomic number
of 26, the atom has 26 protons.
2) What is the nuclear charge of an atom of Fe? Since Fe has 26 protons, the
nuclear charge is +26.
3) How many atomic mass units (amu) do the protons in an atom of Fe weigh?
Since each proton has a mass of 1 amu, the mass of 26 protons is 26 amu.
4) How many electrons does Fe have around its nucleus? The number of
electrons in the atom must equal the number of protons. Since Fe contains 26
protons, it must also contain 26 electrons. If you look at the electron configuration
2-8-14-2 and add up all of those electrons, you will see it adds up to 26 electrons.
5) What is the most common isotope of Fe? Take the average atomic mass of all the isotopes of Fe (55.847) and
round it to the nearest whole number (56). That is the mass number of the most common isotope of iron, Fe-56.
6) How many neutrons are in the nucleus of the most common isotope of Fe? To find the number of neutrons,
take the mass number (which is the number of particles in the nucleus, protons and neutrons combined) and subtract
out the atomic number (the number of protons). There are 56 particles in the nucleus of the most common isotope
(Fe-56), of which 26 are protons (from the atomic number of 26). 56 – 26 = 30 neutrons in the nucleus.
A Bit-O-Practice
Element
Atomic
Number
Atomic
Mass
# protons
#
neutrons
Nuclear
Charge
#electrons
Number of
nucleons
H
C
O
Cl
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5) Isotopes
What is an isotope? ‘Iso’ means ________ ____________, such as in the word ‘isobar’ from earth
science, which was a line of the same pressure (bar = pressure). The thing that is the same for
isotopes is the type of _______________. Not every atom of the same element is identical to
another, their masses can be different. The mass of an atom comes from the mass of the
______________ and _________________. If two atoms are the same element, then they must
have the same number of _________________. For their masses to be different, they must have a
different number of __________________.
Example:
C-12
vs.
C-14
Both are isotopes of carbon. C-12 has a mass of 12 amu and C-14 has a mass of 14 amu. Since
they are both carbon, they both have 6 protons. C-12 has a total mass of 12 amu, 6 of which came
from the 6 protons, so it must have 6 neutrons. C-14 has a mass of 14 amu, 6 amu from the
protons and the rest from 8 neutrons.
Fill in the chart for what is the same between C-12 and C-14
Same
Different
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Distinguishing between different isotopes
It is often required to be specific about what isotope of an element you are referring too and there
are two ways to accomplish this
1) Subscript + Superscript + Symbol:
One way to express an isotope is to include the atomic number (_______________), the atomic
mass (______________________) accompanied with the elements symbol.
2) Symbol – Mass:
H-1
Because all atoms of the same element have the same atomic __________________, it is often
left out and it can simply be written as the elements symbol - mass
Practice: Complete the chart below
Symbol
Atomic #
Mass #
p
n
92
26
e-
143
56
26
34
44
36
S-32
82
207
80
30
34
30
35
44
36
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6) Weighted Average Mass (WAM):
With all of these different isotopes, how do you determine the average mass for an
element?
You are taking a class where you have been doing great, except for a single assignment which you
did not do. Your grading breakdown looks like this
Percent
Grade
Abundance
100
90%
0
10%
You are told to determine your average. For your first attempt at this you simply average the 2
different grades you have:
(100 + 0) / 2 = __________
Realizing that if 90 percent of your grades were 100% right, there is no way that this could be your
overall average. You figure out that you must account for the __________________ of each grade
in your calculations. The way you do this is by multiplying each grade by its percent abundance so
that it reflects all of your good grades. Your second try is more accurate and looks like:
(100 x .90) + (0 x .10) = _____________
Since 90% of your grades were 100, you multiplied 100 by 90%, which is .90 in decimal format.
You did the same for your 0, added the two together and got an overall average of 90%. This is
called your ________________ __________________. You do the same when calculating the
average atomic mass, which is referred to as the Weighted-Average Atomic Mass, or __________
for short. The generic formula for determining the WAM is:
WAM = (massisotope 1 X %/100) + (massisotope 2 X %/100) + (massisotope 3 X %/100) + …
There is one set of parenthesis for each isotope which exists. If there are 2 isotopes, then there will
be 2 sets of parenthesis. If there are 4 isotopes, then there will be 4 sets of parenthesis…etc.
*NOTE: For simplicity, lets round our WAM’s to the thousandths place unless otherwise instructed.
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Examples
There are 4 naturally occurring isotopes of Iron. Complete the missing information in the chart
below;
Mass of
Isotope
(amu)
Notation 1
Symbol – mass #
54
56
57
58
Notation 2
# protons
(atomic #)
# neutrons
(mass # - atomic #)
# electrons
(atomic #)
%
Abundance
in Nature
26
54-26 = 28
26
5.845%
91.754%
2.119%
0.282%
Mass #
Symbol
54Fe
Fe-56
57Fe
Fe-58
Calculate the WAM for iron below
Work (multiplying)
Work (adding)
Unrounded Answer
Rounded w/units
55.90993
LETS TRY ANOTHER ONE!
Nitrogen has 2 naturally occurring isotopes: N-14 (99.33% ) and N-15 (0.67%). What is the WAM
for Nitrogen?
Work (multiplying)
Work (adding)
Unrounded Answer
Rounded w/units
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NOTES ABOUT WAM:
- The rounded atomic mass is the ____________ abundant isotope for that element.
Take a look at the averages in the examples that you did on the previous page. What would
happen if you were to round the WAM’s to the ones place? You would get the most abundant
Isotope for that element!
- The atomic masses are based on C-12 = 12.000 amu
Protons and neutrons do not weigh exactly 1 amu. Neutrons weigh a tiny fraction _____________
than protons do. An atomic mass unit is actually an average mass, found by taking the mass of a
C-12 nucleus and dividing it by 12.
Here are their relative masses
Neutron
Proton
Electron
=1
= 0.99862349
= 0.00054386734
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Student Name:___________________________________ Grades: _____, _____, _____, _____, _____, _____
1) Scientific Method Homework
1) You arrive home on a lovely Tuesday afternoon and grab your CD player to catch up on some tunes. You
slide the headphones on to enjoy the delicious music, but when you press PLAY, nothing happens! You
decide to play the scientific method game to figure out what’s wrong.
1) Match the statements below on the right with the parts of the scientific method listed on the left by
connecting them with drawn lines:
2) List two other possible hypotheses for why the CD player is not working.
a)________________________________________________________________________________
b)________________________________________________________________________________
3) For one of your hypotheses above, explain how you could work through the scientific method to test the
hypothesis:
Chosen Hypothesis:____________________________________________________________________________
Design Experiment to Test Hypothesis:
______________________________________________________________________________________________
______________________________________________________________________________________________
______________________________________________________________________________________________
Expected results if hypothesis is true:________________________________________________________________
______________________________________________________________________________________________
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2) Measurement, Precision and Sig Fig Homework
1) Measure the length of a paper clip on each ruler pictured below. The measurements will not be the same
for each one, due to a difference in precision. Use the same paper clip for all three measurements and record
your readings:
2) For the following measuring devices, record the reading, the precision (place) the measurement was made
to and the number of significant figures in the measurement.
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3) Circle the place where the precision is and underline the significant figures in the measurements below.
Write the number of significant figures in the measurement to the right of each measurement.
Measurement
# Of Sig Figs
Measurement
# Of Sig Figs
Measurement
2 0 0 0 cm
0 . 6 0 0 cm
1 1 . 3 cm
_
2 0 0 0 cm
0 . 0 5 0 9 cm
1 1 . 3 0 cm
_
2 0 0 0 cm
0 . 4 4 0 0 3 cm
3 cm
2 0 0 0. cm
0 . 0 0 0 0 5 6 cm
3 . 0 cm
2 0 0 0 . 0 cm
0 . 0 0 0 9 9 0 cm
3 . 0 0 7 cm
3 0. cm
2 0 0 . 0 0 6 cm
_
3 0 0 0 cm
3 2 . 0 cm
3 0 . 0 2 0 cm
9 0 cm
3 3 . 5 cm
9 7 . 2 8 5 cm
3 3 3 0 2 cm
3 9 0 . 0 7 cm
0 . 0 0 9 5 3 cm
6 8 . 0 0 cm
# Of Sig Figs
4) Write the following numbers, precise to the noted precision or number of significant figures:
Number
Precise to the
nearest…
Answer
Number
Precise to the
nearest…
Forty-two
Tenth
42.0
3 sig figs
Three thousand
2 sig figs
Three hundred
twenty
Seventeen
0.3
3 sig figs
Hundred
Six
Thousandth
Sixteen
thousand
0.4
Answer
4 sig figs
Thousandth
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3) Rounding Homework
Be sure to consider the number of significant figures or precision in each of the following problems.
For this exercise, consider all numbers to be measurements. Include the units in your answers.
Write the UNROUNDED answer first, then the ROUNDED answer, drawing a box around your
rounded answer.
1) ADDITION
Problem
Unrounded Answer
Rounded Answer,
with units
Unrounded Answer
Rounded Answer,
with units
4.732 cm + 16.8 cm + 0.781 cm =
32.0 MW + 0.0059 MW =
0.00372 g + 0.2187 g + 0.44 g =
0.0202 km + 0.0303 km + 0.044 km =
345 mmol + 0.788 mmol =
93.667 cg + 81.1 cg =
2) SUBTRACTION
Problem
22.95 mg – 6.4 mg =
33.728 cL – 1.323 cL =
32.32 J – 0.0049 J =
378.98 kg – 16 kg =
1.00345 km – 0.0023 km =
960 cg – 0.00323 cg =
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3) MULTIPLICATION
Problem
Unrounded Answer
Rounded Answer,
with units
Unrounded Answer
Rounded Answer,
with units
37.66 KW X 2.2 h =
14.922 cm X 2.0 cm =
98.11 kg X 200 m =
381 m X 0.21 m =
143 $/L X 341 L =
200. $/kg X 30 kg =
4) DIVISION
Problem
4792 g / 24 cm3 =
7139 g / 1426 cm3 =
3.00 cal / 300 g =
19.82 g / 24.2 km =
64.77 g / 9.11 mol =
144.0 g / 10 L
F) OK, here is a practical problem in which you will combine all of your skills. The equation you will use is
D = m/v (density = mass / volume). Remember to show a proper numerical setup (with units) and solve,
making sure your final answer is properly rounded for the type of math you did:
1) A ring, supposedly made of pure silver (Ag) has a mass of 20.445 grams. When its volume is taken by water
displacement, it is found to have a volume of 1.95 mL. Calculate the density of the ring:
2) Based on the actual density of silver (Ag) found on Reference Table S, could this ring actually be made out of
silver? Briefly explain your answer:
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Science Is A Verb Review Sheet
1) Measure the length of the line below:
2) Complete the following chart:
Measurement
Precision
# Sig Figs
2000 cm
2100 cm
2000. cm
30.0 g
32.00 mL
320 g
460. mm
371.040 kg
Measurement
Precision
# Sig Figs
0.030
0.001
0.1020
0.00032
0.1230
9.0
9.00
4210
3) Solve and round off the following math problems:
Problem
Unrounded Answer
Rounded Answer
34.21 cm + 1.9 cm =
420 kg + 0.23 kg =
3.345 mL – 2.8 mL =
22.56 g / 9.14 mol =
72.35 cm X 2.88 cm =
2.34 g / 8.9 mL =
23.2 mm X 10 mm =
23.2 mm X 10. mm
REVIEW SHEET ANSWERS
Measurement
2000 cm
2000 cm
2000. cm
30.0 g
32.00 mL
320 g
460. mm
371.040 kg
Problem
Precision
thousand
Thousand
One
Tenth
Hundredth
Ten
One
thousandth
# Sig Figs
1
1
4
3
4
2
3
6
Measurement
Precision
0.030
0.001
0.1020
0.00032
0.1230
9.0
9.00
4210
Thousandth
Thousandth
Ten thou’th
Hund tho’th
Ten thou’th
Tenth
Hundredth
Ten
Unrounded Answer
34.21 cm + 1.9 cm =
36.11
420 kg + 0.23 kg =
420.23
3.345 mL – 2.8 mL =
0.545
22.56 g / 9.14 mol =
2.468271335
72.35 cm X 2.88 cm =
208.368
2.34 g / 8.9 mL =
0.262921348
23.2 mm X 10 mm =
232
23.2 mm X 10. mm
232
4) Atomic Structure (The Nucleus) Day 1
# Sig Figs
2
1
4
2
4
2
3
3
Rounded Answer
36.1 cm
420 kg
0.5 mL
2.47 g/mol
208 cm2
0.26 g/mL
200 mm2
230 mm2
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A) Multiple-Choice Questions: place your answers in the space to the left of each question.
_____1) One atomic mass unit is defined as weighing
a) 1/16 the mass of O-16
b) 1/12 the mass of C-12
c) 1/32 the mass of S-32
d) 1/10 the mass of B-10
Where do you find this information on the Periodic Table?
_____2) How many electrons does it take to weigh the same as a proton?
a) 1
b) 100
c) 957
d) 1836
_____3) Carbon-12 contains 6 protons, 6 neutrons and 6 electrons. Which subatomic particle, if changed,
would change the identity of the element?
a) proton
b) neutron
c) electron
d) all of the above
_____4) A nucleus of Mg-25 contains how many neutrons?
a) 12
b) 13
c) 25
d) 37
Explain how you reached this determination.
_____5) What is the nuclear charge of a nucleus of P-32?
a) +15
b) +17
c) +32
d) +47
Explain how you reached your conclusion.
_____6) How many electrons orbit a nucleus of N-13?
a) 6
b) 7
c) 13
d) 19
Explain why this is.
B) Complete the following table:
Isotope
39
19K
42
20Ca
56
26Fe
232
92U
# Protons
# Neutrons
# Electrons
Nuclear Charge
4) Atomic Structure (The Nucleus) Day 2
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_____A) Which of the following represents isotopes of the same element?
a) 818O and 818O
b) 816O and 818O
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c) 8 O and 9 F
d) 919F and 1019Ne
Explain why the two symbols represent isotopes of the same element:
Explain why ONE of the other choices are NOT isotopes of the same element.
B) Find the most common isotope for each of the following elements:
Element
Atomic Mass (from Periodic Table)
Most Common Isotope
Ca
Br
Zn
Hg
40.08
Ca-40
D) Weight-Average Mass Problems (show all work, round your answer to the thousandths place):
1) A meteor crashes to Earth, is collected and analyzed. To everyone’s surprise, a new element is discovered
with an atomic number of 120. Calculate the weight-average atomic mass for this new element, Ubn
(Unbinnulium). Show all work below.
2) Honors/Bonus. The average atomic mass for thallium, Tl, is 204.41. There are 2 isotopes; Tl-203 and Tl-205.
What is the percent abundance of each isotope?
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