2. Conservation of Mass Video Notes
A. Watch this video and take notes: https://www.youtube.com/watch?v=2S6e11NBwiw
(Use screen shots to help explain parts of the video - minimum 3)
B. Steel Wool Experiment: https://www.youtube.com/watch?v=774TbEUUM-A
Take Notes using screenshots to explain
★ Grey metallic color, thin fibers, rough surface (Original Steel Wool, before being placed in
vinegar)
★ Vinegar is going to take away some of the wax coating the wool, allowing wool to be
exposed to oxygen
★ Balloon is placed over flask, gets pulled inside (chemical reaction)
○ Oxygen reacted to iron
○ Shows law of conservation of mass because the mass stayed relatively the same
before and after the chemical reaction
C. Baking Soda and Vinegar Lab
https://www.youtube.com/watch?v=5o-UjU8l_3M
Describe the results in this experiment
★ Mass of the baking soda balloon and beaker of vinegar was 229.5 g (unmixed)
★ Mass of mixture was 225.9 g (after the reaction)
★ Only lost mass due to human error (air/carbon might have escaped, measurements may be
incorrect, etc…)
D. Watch this reaction: https://www.youtube.com/watch?v=Wwmsy4huZQ0
Questions:
1. What is the Law of Conservation of Mass?
Mass/Matter cannot be created or destroyed in any physical or chemical reaction. It can only
change form.
2. How are all the videos similar?
★ All explain the Law of Conservation of Mass
★ Each give at least 1 example of how it works in a chemical reaction
○ Ex: Video 2, shows chemical reaction of steel wool (dipped in vinegar, exposed to
oxygen), and compares the mass of it before and after the reaction occurred
(masses were very close)
Example:
Explain how this reaction follows the Law of Conservation of Mass
CaCl2 + Na2 S O4 → ___CaSO4 + 2 NaCl
Ca = 1
Cl = 2
Na = 2
SO4 = 1
Explain:
This reaction follows the Law of Conservation of Mass because no mass was gained/lost after
the chemical reaction. Originally, before the reaction occurred, there was one calcium, 2 chlorines,
2 sodiums, and 1 sulfate. After the compounds reacted, the same amount of elements were
formed. All that happened after the chemical reaction was that the reactants formed new
products.
3. Chemistry Test Review
1. What happens to mass when you burn gasoline in an engine?
A. Mass is lost
B. Mass is gained
C. New substances are created
2. In salt water, the SOLUTE is the ______________.
A. Water
B. Salt
C. Glass
3. What happens to matter when it is heated?
A. Molecules slow down and move closer
B. Molecules slow down and move further
C. Molecules move faster and move further apart
4. When iron and sulfur or rocks and sand are MIXED what happens to the properties?
A. stay the same
B. change
5. A _______________ is called a solution made up of metals.
A. Sublimation
B. Condensation
C. Alloy
6. When one element displaces another element in a compound, the reaction is a
_______________ reaction.
A. Synthesis
B. Single Displacement
C. Displacement
7. These 2 ways will speed up the dissolving of a solute:
A. Cool down and grind up the solvent
B. Stir and heat the solution
C. Look at it
8. Chemical reaction in which energy is released in the form of heat is called __________.
A. Endothermic
B. Exothermic
C. Density
9. What happens if you increase the surface area of a solid when dissolving?
A. Dissolves faster
B. Dissolves slower
C. Same
10. The number that comes before a chemical formula (2 H2 0 ) is called the __________
A. Subscript
B. Coefficient
C. Fractions
11. The smallest particles that make up matter (building blocks of matter) is called ________.
A. compound
B. Mixture
C. Atom
12. Iron rusting is an example of _________________.
A. Physical Property
B. Chemical Property
13. Changing directly from a solid to a gas is called ______________.
A. Density
B. Evaporation
C. Sublimation
14. Phase changes (boiling, melting) are called ________________.
A. Physical Changes
B. Chemical Changes
15. What should the coefficient be in the following reaction:
___ Fe + 3 O2 → 2 Fe2O3
A. 2 B. 3 C. 3 D. 4
16. What should the coefficients be in the following reaction:
__Al + ____ HCl → __AlCl3 + ___ H2
A. 2, 2, 2, 2
B. 4, 2, 2, 4
C. 2, 6, 2, 3
17. What should the coefficients be in the following reaction:
__ KClO3 → ___ KCl + __ O2
A. 2, 2, 2, 2
B. 2, 2, 3
C. 4, 4, 6
18. A substance that speeds up a chemical reaction is called a ___________.
A. inhibitor
B. coefficient
C. reactant
D. catalyst
19. When rocks, sand and iron are mixed together, the properties of the final substances are
_______________ to those of the beginning substances.
A. same
B. different
20. Write an essay that explains the difference between a Homogeneous Mixture and a
Heterogeneous Mixture.
21. Explain how to use the Solubility Chart/graph - Use examples
*Review your Solubility assignment
22. Explain the difference between a Single Displacement Reaction and a Double Replacement
Reaction
(Silver nitrate and copper)
23. Explain the phase change chart using a specific example of an ice cube with a mass of 35 g
that completely evaporates.
24. Name compounds with: phosphate, sulfate, carbonate, hydroxide, nitrate, ammonium, chlorate
25. Write the formulas if given the names of compounds.
Atomic Structure
1. Atomic Structure Portfolio
Directions: Construct a flipbook that covers the following categories related to Atomic Structure
and its relationship to the Periodic Table
Reading: h ttps://www.livescience.com/37206-atom-definition.html
*Use this site for notes
Article Notes:
● Atoms → basic units of matter and the defining structure of elements
● Made up of protons, electrons, and neutrons
● Protons and neutrons are heavier than electrons
○ Both are found in the nucleus; center of the atom
● Protons + neutrons have about the same mass
● 1 proton weighs more than 1,800 electrons
● Atoms always have an equal number of protons & electrons
● Adding a proton → new element
● Adding a neutron → isotope or heavier version of atom
● All the mass of the atom is usually found in the nucleus
● Protons: positively charged particles found within the nucleus
● Atomic number of element = number of protons
● Atomic mass - atomic number = number of neutrons
● Atomic number = number of electrons
Examples of Parts of an Atom: (neutral; no charge)
Element Name Atomic Atomic Mass Protons Neutrons Electrons
Number
0 1
Hydrogen 1 1 1 2 2
4 3
Helium 2 4 2 5 4
6 5
Lithium 3 7 3 6 6
7 7
Beryllium 4 9 4 8 8
10 9
Boron 5 11 5 10 10
Carbon 6 12 6
Nitrogen 7 14 7
Oxygen 8 16 8
Fluorine 9 19 9
Neon 10 20 10
1. Cover Page: Atomic Structure and Periodic Table
Atoms are made up of protons,
neutrons, and electrons. The
number of protons, neutrons, and
electrons in an atom depend on
the element from the periodic
table.
2. History of the Atom
Link: h ttps://www.youtube.com/watch?v=NSAgLvKOPLQ&t=490s
Link2:
a. Dalton
● In 1808, Dalton came up with the first scientific experiments that show that matter is
made of tiny particles
○ One of the first people to conduct experiments testing atomic structure
● Dalton thought that atoms were indivisible (smallest things in the universe; can’t be divided
into smaller components)
b. Thomson - V ideo
● In 1987, Thompson and his co-workers discovered the electron after conducting “The
Cathode Ray Tube Experiment”
● Discovered that electrons were much smaller than atoms (atoms are divisible)
● Pictured atoms like “plum pudding” → created model
○ “Dough” was positively charged, electrons were negatively charged
● Thought positive charge was distributed throughout the atom
c. Rutherford
● Discovered protons in 1919
● Found out that atoms had a nucleus (after conducting the gold foil experiment)
○ All the positive charge in an atom was concentrated in the center, not throughout
the entire atom
○ Atoms seemed to be empty space (other than nucleus and electrons)
d. Bohr
● Reasoned there’s a nucleus in the middle, and electrons weren’t randomly distributed
through the atom
○ Instead, the electrons spin around the nucleus in circular orbits (the circles
around the nucleus are the orbital shells)
3. Structure of the Atom
Video
Video2
a. Nucleus, protons, neutrons, electrons
Basic Atomic Structure:
● All atoms have a dense nucleus made up of protons (positively charged) and neutrons (no
charge/neutral)
● Electrons (negatively charged) are found outside of the nucleus in in orbital shells
● The structure of electrons follows the “octet rule”
○ The first ring/orbital can hold up to 2 electrons
○ The second and third orbitals can hold up to 8 electrons
○ Rule mainly applies for the first few rows of the periodic table
■ Examples: hydrogen, helium, nitrogen, oxygen, fluorine, neon, chlorine, argon
b. Atomic Mass
● The atomic mass is made up of protons and neutrons (electrons don’t make up any of the
mass in an atom)
● Majority of mass is found within the nucleus
● Different elements have different atomic masses
○ Ex: Hydrogen = 1, Lithium = 3
c. Charge
● When an atom gains or loses electrons → develop a charge
○ These charged particles are called ions
● Atom loses electrons → positively charged
○ Called “cations”
● Atom gains electrons → negatively charged
○ Called “anions”
d. Valence Electrons
● Valence - outermost shell
○ Valence electrons - electrons found in the outermost shell of the atom (highest
energy, furthest out)
● A valence electron is an outer-shell electron, and can be part of a chemical bond if the
outer shell isn’t fully closed
○ The formation of a shell is 2 for the first shell, 8 for the second shell, and 8 for
the third shell
● When an atom gets rid of/gains an electron, electrons are either taken away or added to
the valence shell
This is an example of a neutral lithium atom. In order for an atom to be considered neutral, the
number of protons has to be equivalent to the number of electrons (charges cancel out).
This is an example of a negatively charged lithium atom. In
order for an atom to be negatively charged (and be
considered as an “ion”, or a negatively charged ion), the
number of electrons needs to be greater than the number
of protons. Protons can’t be taken away from an atom
because doing so changes the element. Therefore, only
electrons can be added/taken away.
This is an example of a positively charged lithium atom. In order for an atom to be positively
charged (and be considered as a “cation”, or positively charged ion), the number of protons needs
to be greater than the number of electrons. Since protons can’t be taken away from the atom, at
least one electron needs to be taken away in order for lithium to have a +1 charge.
***Use models to explain the difference between:
Sodium Chloride and M agnesium Chloride or S odium sulfide and C alcium Sulfide
As you can see, this sodium atom has only one extra
valence electron. On the other hand, the chlorine atom
is missing one electron to complete its outer shell. The
sodium atom will “give up” its extra electron, giving it to
the chlorine atom. Now, both sodium and chlorine have
full, even shells. Both atoms are connected by an ionic bond, therefore, making sodium chloride.
This magnesium atom has
two extra valence electrons.
As previously mentioned, an atom of chlorine only needs one electron to have complete shells. The
magnesium atom “gives away” one electron to each of the chlorine atoms. Finally, after the
electrons have been transferred, the magnesium and chlorine atoms have complete shells. Lastly,
because there’s now an ionic bond, magnesium chloride is made.
The main difference between the two compounds (sodium chloride and magnesium chloride) is that
magnesium chloride requires two atoms of chlorine, whereas sodium chloride requires only one.
This is because magnesium has two extra electrons to get rid of (an atom of chlorine only
“accepts” one electron), while on the other hand, sodium only has one electron to offer.
4. Isotopes
Link: h ttps://phet.colorado.edu/en/simulation/isotopes-and-atomic-mass
a. Provide Example
Isotope: each of two or more forms of the same element that contain equal numbers of protons
…….…...b ut different numbers of neutrons in their nuclei. They differ in atomic mass but not in
…….….. chemical properties.
Above are the three isotopes of hydrogen. In each isotope, there’s a different number of
neutrons and a slightly different mass.
b. How are they used by Scientists?
Isotopes are used by a variety of scientists throughout the field. Since isotopes are variations of
elements, they have many uses in science. For example, radioactive isotopes are used in medicine.
Some radioactive isotopes can stop/alter the development of cancer. Others can be used as a
“tracer” to determine where a certain medicine is metabolized inside the human body. Overall,
isotopes are important in life sciences, including medicine and biology.
5. Families of the Periodic Table
*Describe the life of Mendeleev and how he created the
Periodic Table.
● Born in 1834; came from a large family (lots of siblings)
● Dmitri Mendeleev was the first to create the Periodic Table in
1869
● Said to be inspired by a card game called “Solitaire”
○ In order to organize elements more effectively, wrote
atomic weight and properties of each known element
on a card
● One story states Dmitri came to the realization of the
organization of elements through a dream
○ Visualized elements falling into place of a table
○ Immediately woke up and wrote down what he’d dreamt on paper
○ Shortly after dream → created what was known as the Periodic Table of
Elements
● Was a russian chemist and teacher
● Although scientists already knew of a few elements in the universe, Mendeleev discovered
many more of the unknown
● Arranged chemical elements by atomic mass
*What makes the elements the similar in each family?
Elements in each family are similar because they have the same amount of valence electrons in
their outermost shells. For instance, all alkali metals have one valence electron, making all elements
classified under that group to have similar properties.
*What are some trends in the Periodic Table?
a. Alkali Metals
● Always one extra valence electron (+1 charge)
● Very reactive
○ Most reactive in the periodic table
● All elements found in this group are metals
b. Alkaline Earth Metals
● Always have two extra valence electrons (+2 charge)
○ Can form/be a part of ionic bonds
● Second most reactive group
● When compounds → mixed into solutions, solutions
likely to have a pH higher than 7
c. Halogens
● All have only seven valence electrons; needs one
more electron to have a full outer shell (-1 charge)
● Also very reactive (due to the fact that halogens
only need one more electron)
○ Often found reacting with alkali metals (alkali
elements have one valence electron to give
away; halogens need to receive one)
○ Although quite reactive, reactivity seems to decrease as you go down the
column
d. Noble Gases
● Most elements under this category have full outer shells
○ Considered stable; don’t need to gain or lose electrons
○ Rarely go through chemical bonding (because almost all elements have
complete shells)
As seen in the graph above, a trend is visible between elements regarding each atomic radius.
First and foremost, the atomic radius of an element is the distance from the nucleus to the
orbital of the outermost electron. Usually starting at a peak, the atomic radius starts to decline
as you go left-right of the Periodic Table. For instance, in the first row of the table, starting
from hydrogen (mass = 32), the atomic radius decreases until the next row is reached. A sudden
peak in the data, due to the fact that lithium (mass = 123) starts the next horizontal row
supports the trend. After lithium however, the rest of the elements in the same row have lower
masses. Beryllium has a mass of 90, showing a decline in overall mass. All in all, as shown in the
data, atomic radius decreases in a horizontal row of the Periodic Table.
In addition, the graph displaying the first ionization energy levels of elements shows an opposite
trend than those relating to atomic masses. Generally, first ionization energy is the energy
needed to move a valence electron (highest energy electron in the atom). As the data shows, first
ionization energy increases through a horizontal row of the periodic table. With this in mind,
hydrogen, the first element of the row, starts with a lower first ionization energy of 1312. The
next element, helium, has a much higher number (2372). Starting a new row, Lithium has a low
number (520), whereas the last element present in the same section, neon, has the highest energy
level in the current row (2081). Similarly, sodium, the start of the next section, has a lower
number (496), indicating a trend in the data. Overall, first ionization energy levels of elements
seem to increase, while on the other hand, atomic masses decrease as you go left to right of the
Periodic Table.
6. Choose an article to read from site and summarize:
https://www.livescience.com/37206-atom-definition.html
Article Link: h ttps://www.livescience.com/60377-molecules-cooled-to-50-microkelvin.html
“That’s Cold! Molecules Cooled to a Shade Above Absolute Zero” written by LiveScience
contributor Jesse Emspak goes over a new technique used to cool molecules below absolute zero.
In the experiment, research was conducted on a molecule of calcium monofluoride. In order to
conduct the trial, a group of researchers used a combination of lasers and magnetic fields, with
an ambition to cool the molecule down to a temperature of 50 microkelvin (-273.15℃). Generally,
this experiment was easy for scientists to conduct due to the fact that calcium monofluoride was
used rather than an “artificial” molecule that’s harder to unite such as potassium-rubidium. First
and foremost, lasers were aimed and fired at the molecule. Although one blast cooled the
molecule significantly, greater results could be seeked out by using a magnetic field. Holding the
molecule in place for yet another blast, researchers were able to successfully cool calcium
monofluoride to new limits. As the science shows, a temperature of 50 microkelvin was reached
due to the fact that the molecule’s kinetic energy was lost. Most importantly, with this
knowledge in mind, scientists could discover many new ways to further cool molecules to
unimaginable limits. All in all, this study was significant because scientists found a new way to
instantly change the temperature of natural occurring molecules, aiding in creating uses for the
world’s broad range of molecules.
2. Atomic Structure Mobile/Model
Isotopes
1. Average Atomic Mass Worksheet
1. Rubidium has two common isotopes, 85Rb and 87R b. If the abundance of 85Rb is 72.2% and the
abundance of 87Rb is 27.8%, what is the average atomic mass of rubidium?
85 * 0.722 = 61.37
87 * 0.278 = 24.186
61.37 + 24.186 = 85.556 amu
The average atomic mass of rubidium is about 85.556 amu.
2. Uranium has three common isotopes. If the abundance of 234U is 0.01%, the abundance of 235U is
0.71%, and the abundance of 238U is 99.28%, what is the average atomic mass of uranium?
234 * 0.0001 = 0.0234
235 * 0.0071 = 1.6685
238 * 0.9928 = 236.2864
0.0234 + 1.6685 + 236.2864 = 237.9783 amu
The average atomic mass of uranium is about 237.9783 amu.
3. Titanium has five common isotopes: 4 6T i (8.0%), 47Ti (7.8%), 4 8Ti (73.4%), 49Ti (5.5%), 5 0T i (5.3%). What
is the average atomic mass of titanium?
46 * 0.08 = 3.68
47 * 0.078 = 3.666
48 * 0.734 = 35.232
49 * 0.055 = 2.695
50 * 0.053 = 2.65
3.68 + 3.666 + 35.232 + 2.695 + 2.65 = 47.923 amu
The average atomic mass of titanium is about 47.923 amu.
4. Explain why atoms have different isotopes. In other words, how is it that helium can exist in
three different forms?
Atoms have different isotopes because there can be a different amount of neutrons in an atom;
the mass varies. Although the number of protons and electrons can’t necessarily be changed in
order for an atom to be considered an isotope, neutrons, for example, can. Different isotopes are
based off of the number of neutrons found. Helium can exist in three different forms because of
this. The only thing that’s different between each variety is the number of neutrons found in the
atom. Neutrons exist to stabilize the nucleus – without them, the nucleus would consist of
nothing but positively-charged protons in close proximity to one another. Because there are
different ways of stabilizing the protons, there are different isotopes.
2. The element copper has naturally occurring isotopes with mass numbers of 63 and 65. The
relative abundance and atomic masses are 69.2% and 30.8% respectively. Calculate the average
atomic mass of copper.
63 * 0.692 = 43.596
65 * 0.308 = 20.02
43.596 + 20.02 = 63.616 amu
The average atomic mass of copper is about 63.616 amu.
3. Calculate the average atomic mass of sulfur if 95.00% of all sulfur isotopes are Sulfur-32,
0.76% are Sulfur-33 and 4.22% are Sulfur-34.
32 * 0.95 = 30.4
33 * 0.076 = 2.508
34 * 0.0422 = 1.4348
30.4 + 2.508 + 1.4348 = 34.3428 amu
The average atomic mass of sulfur is about 34.3428 amu.
4. The four isotopes of lead are shown below, each with its percent by mass abundance and the
composition of its nucleus. Using the following data, first calculate the approximate atomic mass of
each isotope. Then calculate the average atomic mass of lead.
82p 82p 82p 82p
122n 124n 125n 126n
1.37% 26.26% 20.82% 51.55%
Pb-204 Pb-206 Pb-207 Pb-208
204 * 0.0137 = 2.7948 206 * 0.2626 = 207 * 0.2082 = 208 * 0.5155 =
amu 54.0956 amu 43.0974 amu 107.224 amu
2.7948 + 54.0956 + 43.0974 + 107.224 = 207.2118 amu
The average atomic mass of lead is about 207.2118 amu.
5. There are three isotopes of silicon. They have mass numbers of 28, 29 and 30. The average
atomic mass of silicon is 28.086amu. What does this say about the relative abundances of the
three isotopes?
Silicon-28 is the most abundant of the three isotopes because its weighted average is closest to
the atomic mass, 28.086 amu.
6. Calculate the average atomic mass of bromine. One isotope of bromine has an atomic mass of
78.92amu and a relative abundance of 50.69%. The other major isotope of bromine has an atomic
mass of 80.92amu and a relative abundance of 49.31%.
Isotope #1:
78.92 * 0.5069 = 40.004548
Isotope #2:
80.92 * 0.4931 = 39.901652
40.004548 + 39.901652 = 79.9062 amu
The average atomic mass of bromine is about 79.9062 amu.
2. Activity: How Old Are Fossils?
Directions: Watch videos, take notes and construct the graphs below using your spreadsheet.
Film:
https://www.bing.com/videos/search?q=radiometric+dating&&view=detail&mid=0913F60FB719BC5
91269 0913F60FB719BC591269&&FORM=VDRVRV
Film #2:
https://www.bing.com/videos/search?q=radiometric+dating&&view=detail&mid=33AAFAE1F005C0
E7E25833AAFAE1F005C0E7E258&&FORM=VDRVRV
Take notes:
● Fossils form when organisms are buried in sand and mud
● As layers of deposits build up, sediments are compressed into rock → organisms form
fossils within the rock
● The younger the rock, the higher it is in the rock layers
● The fossils in the rock layer are the same age as the rock itself
● The gradual breakdown of a radioactive substance in rocks is the “clock” that scientists
uses to measure geological time
○ Cenozoic Era
○ Mesozoic Era
○ Paleozoic Era
● Radioactive isotopes decay into different elements as they emit radiation (ex: Uranium
-238 → Lead-206
● “Half-life”: the time it takes for half of a given quantity of a radioactive isotope to decay
into another isotope
● An isotope with a shorter half-life would be better for calculating the age of a younger
rock
● Isotope with a shorter half life → decays more significantly in a shorter time
● “Radiometric Dating”: a method of determining the ages of fossils using radioactive
isotopes
100
50
25
Isotope #1 12.5
6.25
0 3.125
2300 1.06
4600 .5
6900 .25
9200 .125
11,500 0
13,800
16,100 100
18,400 50
20,700 25
23,000 12.5
Isotope #2 6.25
3.125
0 1.06
1500 .5
3000 .25
4500
6000
7500
9000
10,500
12,000
13,500 .125
0
15,000
Graphs:
Write an Essay that explains which fossil is older: (use your graphs)
As shown in the graphs, Fossil A seemed to be older than Fossil B. Representing Fossil A
was the “Fusarus” isotope, with 18% remaining. On the other hand, Fossil B represented the
“Montanosaurus” isotope, with 35% remaining. To begin with, the data shows that when Fusarus
was 18% decayed, it was approximately 6,000 years old. Different from the first isotope, Fossil B,
the Montanosaurus, would be about 2,200 years old considering that it was 35% decayed.
Generally, the graphs show the rate of decay for both fossils. Likewise, as seen in the data, it
takes about 23,000 years for the Fusarus to be fully decayed (0% remaining), whereas it takes
only 15,000 years for Montanosaurus to reach its endpoint (0% remaining). Clearly, this shows
that Fossil A is older, due to the fact that it takes longer for it to decay compared to Fossil B.
Furthermore, after decaying 50%, the Fusarus would be approximately 2,300 years old. In
contrast to the Fusarus, the Montanosaurus would be approximately 1,500 years old after
decaying 50%. Therefore, as seen in the graphs and data tables, the Fusarus is much older than
the Montanosaurus, with an 800-year difference after both fossils have decayed at least 50%.
3. Isotopes Quiz Review
Isotope - Radiometric Dating
Directions: Use the following Isotopes and decay rates to determine the age of the fossils in the
room.
Isotope #1 Isotope #2
Years % Remaining Years (millions) % Remaining
0 100 0 100
2800 50 3.2 50
5600 25 6.4 25
8400 12.5 9.6 12.5
11,200 6.25 12.8 6.25
16 3.125
14,600 3.125 1.56
19.2 0.78
17,400 1.56 22.4 0.39
25.6 0.19
20,200 0.78 28.8 0.095
23,000 0.39 32 0
35.2
25800 0.19
28,600 0.095
31,400 0
Questions:
Isotope #2:
1. How old is each Isotope #1: About 6
fossil if there is About 5000 million years
29% remaining? years old old
Isotope #2:
2. How old is each Isotope #1: About 4
fossil if there is About 4000 million years
46%? years old old
3. How much of About 10% is
Isotope #1 is remaining
remaining if the
fossil is 8000
years old?
4. How much of About 8% is
Cabrerianite is remaining
remaining if the
fossil is 11,000
years old?
Isotope #1: Isotope #2:
5. How old is each About 5,500 About 6.5
fossil if there is years old years old
23% remaining of
both isotopes?
% remaining Isotope #1 Isotope #2
Fossil A About 4900 About 5.5 mil
32% remaining years old years old
Fossil B 18% About 7000 About 7.5 mil
remaining years old years old
75% About 1500 About 2 mil years
Fossil C remaining years old old
65% About 2400 About 3 mil years
Fossil D remaining years old old
Fossil E 20% About 6500 About 6.5 mil
remaining years old years old
42% About 4500 About 4 mil years
Fossil F remaining years old old
Average Atomic Mass Practice Problems
1. Calculate the atomic mass of lead. The four lead isotopes have atomic masses and relative
abundances of 203.973 amu (1.4%), 205.974 amu (24.1%), 206.976 amu (22.1%) and 207.977 amu
(52.4%).
How many neutrons would each isotope have in its nucleus?
Isotope #1: 203.973 * 0.014 = 2.855622
Isotope #2: 205.974 * 0.241 = 49.639734
Isotope #3: 206.976 * 0.221 = 45.741696
Isotope #4: 207.977 * 0.524 = 108.979948
2.855622 + 49.639734 + 45.741696 + 108.979948 = 207.217 amu
The average atomic mass of lead is 207.217 amu. Isotope #1 would have 122 neutrons, isotope #2
would have 124 neutrons, isotope #3 would have 125 neutrons, and isotope #4 would have 126
neutrons.
2. Calculate the average atomic mass of sulfur if 95.00% of all sulfur atoms have a mass of 31.972
amu, 0.76% has a mass of 32.971amu and 4.22% have a mass of 33.967amu.
How many neutrons would each isotope have in its nucleus?
Isotope #1: 31.972 * 0.95 = 30.3734
Isotope #2: 32.971 * 0.0076 = 0.2505796
Isotope #3: 33.967 * 0.0422 = 1.4334074
30.3734 + 0.2505796 + 1.4334074 = 32.057387 amu
The average atomic mass of sulfur is 32.057387 amu. Isotope #1 has 16 neutrons, isotope #2 has
17 neutrons, and isotope #3 has 18 neutrons.
4. Isotopes Quiz
I sotope A
Years Percent Isotope
0 100
5730 50
11,460 25
17,190 12.5
22,920 6.25
28,650 3.125
34,380 1.06
40,110 .5
45,840 .25
51,570 .125
57,300 0
Hint: Remember to add gridlines
Graph: (place graph here)
Questions: (Use your graph above to answer the questions below)
1. How old is the following fossil?
Fossil A - 73% of Isotope A remaining
∗5 ,000 years old
2. How old is the following fossil?
Fossil B - 15% of Isotope A remaining
∗15,000 years old
3. What percentage of Isotope A is remaining if the fossil is 1200 years old?
(Use your graph)
∗I f the fossil is 1,200 years old, there will be 94% of Isotope A remaining.
Average Atomic Mass Calculations
1. Naturally occurring chlorine that is put in pools is 75.53 percent 35Cl (mass = 34.969 amu)
and 24.47 percent 37Cl (mass = 36.966 amu). Calculate the average atomic mass of chlorine.
3 5 Cl: 75.53/100= 0.76%
0.76 x 34.97 = 26.58%
→ 2 6.58% + 8.88% = 35.46%
37 Cl: 24.47/100= 0.24%
0.24 x 36.97 = 8 .88%
∗The average atomic mass of chlorine is 35.46 amu.
2. Calculate the atomic mass of silicon. The three silicon isotopes have atomic masses and
relative abundances of 27.9769 amu (92.2297%), 28.9765 amu (4.6832%) and 29.9738 amu
(3.0872%).
Silicon Isotope #1: 9 2.23/100= 0.92%
0.92 x 27.98= 25.74%
Silicon Isotope #2: 4.7/100= 0.04% ------> 25.74 + 1.16 + 0.9 = 2 7.8%
0.04 x 28.98= 1 .16%
Silicon Isotope #3: 3.09/100= 0.03
0.03 x 29.97= 0.9%
∗The atomic mass of silicon is 27.8 amu.
Writing:
Use one of the examples above to discuss how you determine the number of neutrons for each
isotope. You also need to discuss how the %abundance contributed to the Average Atomic Mass
of the element. (HINT: Think of the M&M Lab!)
Out of the three isotopes of Silicon, each one has the same number of protons (14) but a
different number of neutrons. Si-27 has an atomic mass of 27.9769 amu, meaning there are 13
protons in the nucleus of this isotope. Si-28 has an atomic mass of 28.9765 amu, meaning there
are 14 neutrons in the nucleus. Lastly, Si-29 has an atomic mass of 29.9738 amu, meaning there
are 15 neutrons in the nucleus.
Furthermore, in order to calculate the average atomic mass of an element, the isotopes of
the element must be taken into consideration. The atomic mass shown on the Periodic Table of
Elements is representing an average of the atomic masses and abundances of the element’s
isotopes. In this example, Si-27 has an atomic mass of 27.9769 and a relative abundance of
92.2297%. Therefore, 27.9769 X 0.922297 determines the mass percentage of Si-27: 25.8%.
Secondly, Si-28 has an atomic mass of 28.9765 and a relative abundance of 4.6832%, making the
mass percentage 1.36%. Lastly, Si-29 has an atomic mass of 29.9738 and a relative abundance of
3.0872%, making the mass percentage 0.925%. By adding 25.8030109393, 1.357027448, and
0.9253511536, the average atomic mass of Silicon, 28.085 amu, can be determined.
Moving on, the abundance of each isotope contributes in determining the average atomic
mass of Silicon, as this percentage represents the quantity of each isotope. Two different types
of M&M’s can be used as an example. In the isotope simulating experiment we conducted in class,
plain M&M’s represented the most common isotope and pretzel M&M’s represented the other
isotope. To calculate the mass of each group of M&M’s, they were weighed using a triple beam
balance. Then, to calculate the average mass of Isotope #1, the total mass, 35.8, was divided by
the number of plain M&M’s, 42, which came out to be 0.85 grams. For Isotope #2, the total mass
was 19.1 and the number of pretzel M&M’s was 8, giving an average mass of 2.39 grams. Next, to
calculate the percent abundance of each isotope, the number of the plain M&M’s were divided by
the total number of the plain and pretzel M&M’s combined, meaning the percent abundance of
Isotope #1 is 84% and the Isotope #2 is 16%. Finally, to calculate the average atomic mass of the
M&M’s, the mass and percent abundances of both isotopes must be added together and then
divided by 100. Thus, the average atomic mass of the M&M’s is 1.0324, which is closer to the
average atomic mass of Isotope #1 or the plain M&M’s. This makes sense as Isotope #1
represents the most common isotope and is the most abundant. Given the facts above, the
isotopes of an element play a major role in determining the average atomic mass of the element.
Motion
1. Telling a Story Using Velocity
Directions: Work in a group to tell a story of a classmate in motion. You must include 3 turns
(change in direction) and 3 different velocities. Your story must also have an amount of time
where the classmate does not move. What did the person do when they stopped? Where were
they going?
Data Table:
Example: Velocity = Distance/Time
V = 12 m/3 sec
V = 4 m/sec.
Description Distance (m) Time (sec.) Velocity (m/s)
Walking: Classroom to locker #902 3.75 m 3 sec V= 3.75/3 = 1.3
Hopping: Locker 902 to Water 7.4 m 5 sec V= 7.4/5 = 1.5
Fountain
Skipping: Water fountain to end of the 5 m 5 sec V= 5/5 = 1
ramp
Jogging (from end of ramp to top of 11 m 3.2 sec V= 11/3.2 = 3.4
ramp) - turn to left (where science
post is located on the wall)
Crawling: from poster to locker 1314 11 m 12 sec V= 14/12 = 1.2
Cartwheeling: From locker 1314 to 6 m 6.5 sec V= 6/6.5 = 0.9
Heart Smart poster in front room 150
Graph: (X-axis is Time;
y axis is Distance)
Story:
It was a normal day at Oz Middle School, and period 7 was just ending, which meant Jillian’s
school day was ending. However, she needed to grab her weapons before going on the dangerous
adventures ahead. She walked cautiously from Scarecrow Lopez’s Science classroom to her locker:
#902. It was an approximate distance of 3.75 meters, and it took the brave warrior 3 seconds (for
evil scientific calculations: Velocity - 1.3 m/sec). Jillian’s next quest was to hydrate at the drinking
well, which was located at the center of Munchkin Village, before braving a long journey to her
classmate’s home. She hopped over her little friends for 5 seconds until she made it to Dorothy’s
house, which was 7.4 m away. Skipping, she then made her way to the start of the Yellow Brick
Road. Unfortunately, the flying monkeys blocked her way to a wanted sign she wanted to observe.
She jogged, dodging the monsters for 11 m in 3.2 seconds. Jillian looked up at the poster to see
her best friend’s name and a reward:
Jillian was absolutely shocked, but
she had to focus on the quest. But it
was not over, as fireballs were being
thrown at her by the Wicked Witch of the West. Jillian ducked under the danger and made
it to Dorothy’s home, locker #1314 (11 meters, 12 seconds). Her final quest was to save Toto from
a ditch and greet the Wizard of Oz: Mr. Runte. Ducking and swiveling, Jillian reached out and
scooped the furry black dog up, and gazed up at the Emerald Castle. She was filled with
happiness to see her leader. After that, everyone lived happily ever after.
THE END
2. Velocity Project
1. Define the following terms and include pictures if possible:
Motion - A movement or Speed - A way of measuring Position - T he locality of an
change in a position or time.
how fast or slow something is object to a certain point of
moving or being done. origin of a coordination
system.
Distance - R efers to how Acceleration - R ate of change Terminal Velocity - Highest
much ground an object has
of velocity of an object with velocity that an object can
respect to time. attain as it
falls
covered during its time of through a fluid.
motion.
Time - M easure of duration Initial Velocity - T he velocity Displacement - R efers to how
and the
intervals of an object before far out of place an object is.
acceleration causes a change.
between them.
Velocity - The rate that the Final Velocity - T he velocity at Key Metric units -
position of an object changes
relative to time. the final point of time. For speed and velocity:
➔ Meters per second
(m/s)
➔ Kilometers per hour
(km/h)
2. What is the difference between Speed and Velocity? Explain using an example in your own
words.
∗ The difference between speed and velocity is that speed measures
the distance an object travels in a certain amount of time, while
velocity measures the rate at which an object changes positions. A
commonly used example to portray the differences is with a race car
track. In short, imagine a race car driver driving 500 miles for 3.14
hours, and starting and finishing at the same point. To find the average
speed, you would use the formula total distance/time. In this case, the
race car driver’s average speed was 159 miles/hour. On the other
hand, for average velocity, one would use the formula displacement/time. Since the driver starts
and finishes at the same position, that means there is no displacement, meaning that the average
velocity would be 0 miles/hour. Given these points, speed is a way of measuring how fast or slow
something is moving or being done, while velocity is the rate that the position of an object
changes relative to time.
3. Pick 2 cities (minimum 500 miles apart) in the United States or world and construct a data table
and graph showing the amount of hours that it would take to travel between the 2 cities with
the following modes of transportation:
San Francisco Bay, Fremont, California → Dubai, United Arab Emirates
Distance: 8,092 miles
A. Usain Bolt ~ 27.8 mph
V = D/T
V = 8,092 mi/27.8 mph
V = 291.1 hrs
B. Model T Ford ~ 45 mph
V = D/T
V = 8,092 mi/45 mph
V = 179.8 hrs
C. Hindenburg ~ 84 mph
V = D/T
V = 8,092 mi/84 mph
V = 96.3 hrs
D. Tesla ~ 155 mph
V = D/T
V = 8,092 mi/155 mph
V = 52.2 hrs
E. Shanghai Maglev (fastest train) ~ 375 mph
V = D/T
V = 8,092 mi/375 mph
V = 21.6 hrs
F. F35 Fighter Jet ~ 1,199 mph
V = D/T
V = 8,092 mi/1,199 mph
V = 6.8 hrs
G. USS Nautilus [just pretend there is only ocean between the cities :)]~ 26 mph
V = D/T
V = 8,092 mi/26 mph
V = 311.2 hrs
Time (Hours) Transportation (@ top speed)
291.1 Usain Bolt
Data Table: 179.8
96.3 Model T Ford
52.2 Hindenburg
21.6
6.8 Tesla
311.2 Shanghai Maglev
F35 Fighter Jet
Graph:
USS Nautilus
5. Determine and graph an 18% increase in Velocity for each vehicle - Show how the Times would
be affected by the increase in speed. Show a double bar graph with the 2 different times for
each vehicle.
H. Usain Bolt ~ 27.8 mph × 18% = 33 mph
V = D/T
V = 8,092 mi/33 mph
V = 245.2 hrs
I. Model T Ford ~ 45 mph × 18% = 53.1 mph
V = D/T
V = 8,092 mi/53.1 mph
V = 152.4 hrs
J. Hindenburg ~ 84 mph × 18% = 99.1 mph
V = D/T
V = 8,092 mi/99.1 mph
V = 81.7 hrs
K. Tesla ~ 155 mph × 18% = 182.9 mph
V = D/T
V = 8,092 mi/182.9 mph
V = 44.2 hrs
L. Shanghai Maglev ~ 375 mph × 18% = 442.5 mph
V = D/T
V = 8,092 mi/442.5 mph
V = 18.3 hrs
M. F35 Fighter Jet ~ 1,199 mph × 18% = 1414.8 mph
V = D/T
V = 8,092 mi/1414.8 mph
V = 5.7 hrs
N. USS Nautilus ~ 26 mph × 18% = 30.7 mph
V = D/T
V = 8,092 mi/30.7 mph
V = 263.6 hrs
Graph:
6. Use a math calculation to show how long it would take the F35 Fighter Jet to get to…
A. Sun ~ Distance: 93,000,000 miles
V = D/T
V = 9.3 × 10^7 miles / 1,199 mph
V = 7.75646372 × 10^4 hours
∗ It would take the F35 Fighter Jet, going at its top speed of 1,199 mph, 7.75646372 × 10^4 hours
to reach the Sun from Earth.
B. Saturn ~ Distance: 746,000,000 miles
V = D/T
V = 7.46 × 10^8 miles / 1,199 mph
V = 6.221851543 × 10^5 hours
∗ It would take the F35 Fighter Jet, going at its top speed of 1,199 mph, 6.221851543 × 10^5
hours to reach Saturn from Earth.
C. Neptune ~ Distance: 2,700,000,000 miles
V = D/T
V = 2.7 × 10^9 miles / 1,199 mph
V = 2.251876564 × 10^6 hours
∗ It would take the F35 Fighter Jet, going at its top speed of 1,199 mph, 2.251876564 × 10^6
hours to reach Neptune from Earth.
3. Velocity Worksheet
1. What is the average speed of a cheetah that sprints 100 m in 4 s? How about if it
sprints 50 m in 2 s?
V = D/T
V = 100 m/4 s
V = 25 m/s
V = D/T
V = 50 m/2 s
V = 25 m/s
The average speed of a cheetah that sprints 100 meters in 4 seconds is 25m/s. If the
cheetah
sprints 50 meters in 2 seconds, it has a velocity of 25m/s.
2. If a car moves with an average speed of 60 km/hr for an hour, it will travel a distance of
60 km. How far will it travel if it continues this average rate for 4 hrs?
D = T * V
D = 4 hrs * 60 km/hr
D = 240 km/hr
The car will travel 240 km/hr if it continues at this average rate.
3. A runner makes one lap around a 200 m track in a time of 25.0 s. What was the runner's
average speed? Answer: 8.0 m/s
V = D/T
V = 200 m/25 s
V = 8 m/s
The runner’s average speed was 8 m/s.
4. Light and radio waves travel through a vacuum in a straight line at a speed of very nearly
3.00 × 108 m/s. How far is light year (the d istance light travels in a year)? Answer: 9.50
× 101 5 m.
D = T * V
D = 365 days * 3.00 × 108 m/s
D = 31557600 seconds * 3.00 × 108 m/s
D = 3.15 * 107 s econds * 3.00 × 108 m/s
D = 9.5 * 101 5 m
The distance light travels in a year is 9.5 * 1015 m.
5. A motorist travels 406 km during a 7.0 hr period. What was the average speed in km/hr
and m/s? Answers: 58 km/hr, 16 m/s.
V = D/T
V = 406 km/7 hrs
V = 58 km/hr
V = D/T
V = 406000 km/25200 s
V = 16 m/s
The average speed is 58km/hr, or 16 m/s.
6. A bullet is shot from a rifle with a speed of 720 m/s. What time is required for the bullet
to strike a target 3240 m away? Answer: 4.5 s.
T = D/M
T = 3240m/720m/s
T = 4.5s
4.5 seconds are required for the bullet to strike a target 3240 meters away.
7. Light from the sun reaches the earth in 8.3 minutes. The speed of light is 3.0 × 108 m/s.
In kilometers, how far is the earth from the sun? Answer: 1.5 × 108 km.
D = T * V
D = 4.98 * 102 s * (3 * 108 m/s)
D = (14.94 * 1010 m)/103
D = (1.494 * 1011 m)/103
D = (1.5 * 1011) /103
D = 1.5 * 108 km
The earth is 1.5 * 108 km from the sun.
8. *An auto travels at a rate of 25 km/hr for 4 minutes, then at 50 km/hr for 8 minutes, and
finally at 20 km/hr for 2 minutes. Find the total distance covered in km and the average
speed for the complete trip in m/s. Answers: 9 km, 10.7 m/s.
D = T * V
D = 0.07 hrs * 25 km/hr
D = 1.75 km
D = T * V
D = 0.13 hrs * 50 km/hr
D = 6.5 km
D = T * V
D = 0.03 hrs * 20 km/hr
D = 0.6 km
Total Distance = 8.85 → 9 km
Total Time = 0.23 hrs
Average Speed = Total Distance/Total Time
Average Speed = 8.85 km/0.23 hrs
Average Speed = 8850 km/0.23 hrs
Average Speed = 8850 km/828 s
Average Speed = 10.7 m/s
The total distance is 9 km and the average speed is 10.7 m/s.
9. *If you traveled one mile at a speed of 100 miles per hour and another mile at a speed of
1 mile per hour, your average speed would not be (100 mph + 1 mph)/2 or 50.5 mph. What
would be your average speed? (Hint: What is the total distance and total time?) Answer:
1.98 mph.
T = D/V
T = 1 mi/100 mph
T = 0.01 hrs
T = D/V
T = 1 mi/1 mph
T = 1 hr
Total Distance = 2 miles
Total Time = 1.01 hrs
Average Speed = Total Distance/Total Time
Average Speed = 2 mi/1.01 hrs
Average Speed = 1.98 mph
Your average speed would be 1.98 mph.
10. *What is your average speed in each of these cases?
a. You run 100 m at a speed of 5.0 m/s and then you walk 100 m at a speed of 1.0
m/s.
T = D/V
T = 100 m/5 m/s
T = 20 s
T = D/V
T = 100 m/1 m/s
T = 100 s
Total Distance = 200 m
Total Time = 120 s
Average Speed = Total Distance/Total Time
Average Speed = 200 m/120 s
Average Speed = 1.7 m/s
Your average speed would be 1.7 m/s.
b. You run for 100 s at a speed of 5.0 m/s and then you walk for 100 s at a speed
of 1.0 m/s. Answers: 1.7 m/s, 3.0 m/s.
D = T * V
D = 100 s * 5 m/s
D = 500 m
D = T * V
D = 100 s * 1 m/s
D = 100 m
Total Distance = 600 m
Total Time = 200 s
Average Speed = Total Distance/Total Time
Average Speed = 600 m/200 s
Average Speed = 3 m/s
Your average speed would be 3 m/s.
11. *A race car driver must average 200 km/hr for four laps to qualify for a race. Because
of engine trouble, the car averages only 170 km/hr over the first two laps. What average
speed must be maintained for the last two laps?
x = Average Speed
170 + 170 + x + x = 800
340 + 2x = 800
2x = 460
x = 230 km/hr
An average speed of 230 km/hr must be maintained for the last two laps in order for the
driver to
qualify for a race.
12. *A car traveling 90 km/hr is 100 m behind a truck traveling 50 km/hr. How long will it
take the car to reach the truck?
T = D/V
T = 0.1 km/40km/hr
T = 0.0025 hrs → 0.15 minutes → 9 seconds
It will take 9 seconds for the car to reach the truck.
13. The peregrine falcon is the world's fastest known bird and has been clocked diving
downward toward its prey at constant vertical velocity of 97.2 m/s. If the falcon dives
straight down from a height of 100. m, how much time does this give a rabbit below to
consider his next move as the falcon begins his descent?
T = D/M
T = 100 m/97.2 m/s
T = 1 s
This gives the rabbit below only about 1 second to consider his next move.
More Speed and Velocity Problems
14. Hans stands at the rim of the Grand Canyon and yodels down to the bottom. He hears his
yodel back from the canyon floor 5.20 s later. Assume that the speed of sound in air is
340.0 m/s. How deep is the canyon?
D = T * V
D = 5.2 s * 340.0 m/s
D = 1768 m
The canyon is about 1768 meters deep.
15. The horse racing record for a 1.50 mi. track is shared by two horses: Fiddle Isle, who ran
the race in 143 s on March 21, 1970, and John Henry, who ran the same distance in an
equal time on March 16, 1980. What were the horses' average speeds in:
a. mi/s?
V = D/T
V = 1.5 mi/143 s
V = 16.9 mi/s
V = D/T
V = 1.5 mi/143 s
V = 16.9 mi/s
Total Distance = 3 miles
Total Time = 286 seconds
Average Speed = Total Distance/Total Time
Average Speed = 3 mi/286 s
Average Speed = 16.9 mi/s
The horses’ average speeds were 16.9 mi/s.
b. mi/hr?
Total Distance = 3 miles
Total Time = 286 seconds → 0.08 hrs
Average Speed = Total Distance/Total Time
Average Speed = 3 mi/0.08 hrs
Average Speed = 37.5 mi/hr
The horses’ average speeds were 37.5 mi/hr
16. For a long time it was the dream of many runners to break the "4-minute mile." Now
quite a few runners have achieved what once seemed an impossible goal. On July 2, 1988,
Steve Cram of Great Britain ran a mile in 3.81 min. During this amazing run, what was
Steve Cram's average speed in:
a. mi/min?
Total Distance = 1 mile
Total Time = 3.81 minutes
Average Speed = Total Distance/Total Time
Average Speed = 1 mi//3.81 min
Average Speed = 0.3 mi/min
Steve Cram’s average speed was 0.3 mi/min.
b. mi/hr?
Total Distance = 1 mile
Total Time - 3.81 minutes → 0.06 hrs
Average Speed = Total Distance/Total Time
Average Speed = 1 mi/0.06 hrs
Average Speed = 16.7 mi/hr
Steve Cram’s average speed was 16.7 mi/hr.
17. It is now 10:29 a.m., but when the bell rings at 10:30 a.m. Suzette will be late for French class for
the third time this week. She must get from one side of the school to the other by hurrying
down three different hallways. She runs down the first hallway, a distance of 35.0 m, at a speed
of 3.50 m/s. The second hallway is filled with students, and she covers its 48.0 m length at an
average speed of 1.20 m/s. The final hallway is empty, and Suzette sprints its 60.0 m length at a
speed of 5.00 m/s.
a. Does Suzette make it to class on time or does she get detention for being late again?
T = D/M
T = 35 m/3.5 m/s
T = 10 seconds
T = D/M
T = 48 m/ 1.2 m/s
T = 40 seconds
T = D/M
T = 60 m/ 5 m/s
T = 12 seconds
Total Time = 10 + 40 + 12 = 62 seconds = 1 minute and 2 seconds
Suzette does not make it to class on time; it takes her 1 minute and 2 seconds to get to
class.
b. Draw a distance vs. time graph of the situation. (Assume constant speeds for each
hallway.)
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(FINAL) Taruni Singanamala (Class of 2022) - Blue Science Portfolio (1)
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