Chemistry I
Matter: Atomic Structure and Bonding
Chemistry Focus: How does the chemical structure of matter
affect its properties?
Chemistry Big Idea: All matter consists of particles that are in constant,
random motion. Matter can undergo both physical and chemical change.
The Guiding Questions
1. What is matter?
2. How can matter change (or not change)?
3. What is the difference between a pure substance and a mixture?
4. How can substances be separated?
What is matter?
Write your ideas below.
How can we explain and show these observations at a molecular level?? Uses of molecular modeling
The Particle Model of Matter
http://preparatorychemistry.com/KMT_flash.htm
1. All matter is made up of __________________________
2. Particles are in ______________________________
3. The motion of the particles is ________________________ to the temperature.
As temperature _________________, the average energy of the particles
_________________.
4. Particles are ___________________________ by electrostatic forces.
Particles have __________________________energy and are in constant motion.
The more energy particles have, the faster they move and the farther apart
they are.
Chemistry I
Matter: Atomic Structure and Bonding
Comparing Solids, Liquids and Gases
Go to the pHet
“States of Matter
http://phet.colorado.edu/en/simulation/states-of-matter-basics
simulation
Basics”
Directions:
1. Experiment with States of Matter Basics and then take notes below including illustrations
that describes “differences and similarities between solids, liquids and gases on a
molecular level”.
Phase of Matter
Shape
Volume
Flow
Compressibility
Example
Solids
Liquids
Gases
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Chemistry I
Matter: Atomic Structure and Bonding
Shape – a definite shape means the substance will keep its shape. An indefinite shape means the
substance will take the shape of the container it is kept in.
Volume – a definite volume means the volume of substance does not change. An indefinite volume means the
substance will expand to fill its container.
Flow – yes or no? If a substance can flow, it can be poured from one container to another.
Compressibility – can the substance be squeezed into a smaller amount of space?
2. Using the simulation, try to change the phase of one of the substances. For example, change
liquid water to solid or gas.
a. Write a summary of your results.
b. See if you can use similar procedures on all the materials. How else can you make a
substance change phase? Are all the conditions the same for all of the materials?
Explain.
Changes of Phase (sometimes called Changes of State)
When a pure substance is heated (or cooled), a change of phase will occur at a specific
temperature. A good example is water, which we know melts at 0oC and boils at 100oC.
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Chemistry I
Matter: Atomic Structure and Bonding
Label the diagram: transpiration, evaporation, condensation, precipitation, percolation, runoff, ocean
water. Circle the words that represent a change of phase.
Changes of phase are described using scientific vocabulary. Complete the diagram below by
labeling the changes between
solid, liquid and gas phases.
Exothermic changes – are
changes where heat energy is
removed from the substance.
Color the arrows indicating
exothermic changes RED.
Endothermic changes – are
changes where heat energy is
absorbed by the substance.
Color the arrows indicating
endothermic changes BLUE.
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Chemistry I
Matter: Atomic Structure and Bonding
For the above changes of state, complete the table:
Macroscopic view
(observatons)
Molecular view
(what is happening at a
molecular level?)
Symbolic view
(how can we use symbols to show this
change?)
H20(l)  H2O (g)
boiling
H20(g)  H2O (l)
H20(g)  H2O (s)
H20(s)  H2O (g)
H20(l)  H2O (s)
H20(s)  H2O (l)
Plasma is often called the “fourth state of matter” and the universe described as a “plasma
universe”.
Research: What is a plasma, and explain why we call our universe “the plasma universe”.
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Chemistry I
Matter: Atomic Structure and Bonding
Heating Curve of Pure Water
a) Indicate the regions of the
graph where water is a solid, a
liquid and a gas.
b) Label the boiling point and
melting point on the y-axis.
c) What do you notice about
the temperature during a change of
phase?
d) Why do you think this is
happening?
Physical Changes and Properties
What is a physical change? List some examples.
What is a physical property? List and explain some examples.
How does this
diagram show a
physical change?
Chemical Changes and Properties
What is a chemical change? List some examples.
What is a chemical property? List and explain some examples.
How does this
diagram show a
chemical change?
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Chemistry I
Matter: Atomic Structure and Bonding
Based on the above diagrams, define each term and give some examples.
Definition
Pure substance
Examples
Mixture
Homogenous mixture
Heterogeneous mixture
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Chemistry I
Matter: Atomic Structure and Bonding
Vocabulary
By the end of this topic, you should be able to define and correctly use the following terms:
Matter
Physical Change
Physical property
Conductivity
Density
Boiling Point
Freezing Point
Melting Point
Condensation
Evaporation
Freezing
Exothermic
Endothermic
Pure substance
Mixture
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Chemistry I
Matter: Atomic Structure and Bonding
Chemistry Focus 2: Atomic Structure and Bonding
What is matter made of? What determines the physical
and chemical properties of water?
All matter is composed of tiny particles called atoms. Atoms combine
chemically to form compounds with distinct physical and chemical properties.
BRAINSTORM – what do you know about . . .
What are atoms made of?
What is unique about the atoms of each kind of element?
Label the diagram and write your ideas below.
Complete the following table:
Electric Charge
Relative Mass
Location
Proton
Neutron
Electron
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Chemistry I
Matter: Atomic Structure and Bonding
Activity – Building Atoms
For this activity you will need to run the “Build an Atom” applet:
http://phet.colorado.edu/en/simulation/build-an-atom
Part 1 – Learning to use the applet
1) The first atom you will construct will be a hydrogen atom. Hydrogen atoms consist of only one proton
and one electron.
a) Start the applet and make sure you select the “Build Atom” tab in the top left of the screen.
b) Click on the
icons next to “Symbol”, “Mass Number” and “Net Charge” to expand the boxes as
shown below.
c) Use the mouse to drag a proton and an electron from the baskets to the atom diagram. When
finished your screen should look like this
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Chemistry I
Matter: Atomic Structure and Bonding
Part 2 – Learn about atomic number and mass number
The notation (symbol) for the hydrogen atom you constructed previously should look
like the diagram below. The elemental symbol for hydrogen is “H”
the red “1” represents the atomic number of the element. This is the number of
protons in the nucleus. The number of protons determines the identity of the element. All
hydrogen atoms have ONE proton.
2) Now we will construct an atom of Helium
a) Drag one more proton and one more electron to your atom. Write the notation for helium
and note any changes in the information provided by the applet.
b) Drag two neutrons to your atom. Draw a diagram of the atom below. Note any changes in
the information provided by the applet.
The notation for the helium atom you constructed should look like this:
c) What is the atomic number of helium? _________
d) What does this number represent?___________
The “4” in the notation represents the mass number for this Helium atom. The mass number is
equal to the total number of protons and neutrons.
e) When you first added the neutrons to the helium atom, you should have noticed a change
in the stability of the atom. Why do you think neutrons are required for the nucleus to be
stable?
f) Add neutrons to the atom you are currently working on. Remove them again. What
number changes? ________________________ What number does not change? _____________________
Does the type of element depend on the number of neutrons present? Explain.
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Chemistry I
Matter: Atomic Structure and Bonding
Part 3 – Learn about ions
3)
First construct an atom of oxygen. Oxygen has an atomic number of 8
a) How many protons will you need? _____________
b) Keep adding neutrons until the atom becomes stable. Then add 8 electrons. The atom is
now neutral. Neutral atoms have balanced electrical charges. This means the number of
positive protons = the number of negative electrons. Write the notation for this atom
below.
c) Notice that the “net charge” window shows that the charges are balanced by indicating a
net charge of zero. A zero is also written above and to the right of the element symbol in
the notation. This zero indicates the net charge of the atom and is not normally written for
neutral atoms (if nothing is written, it is assumed to be zero). However, electrons can be
gained or lost to form ions.
An ion is an atom with an electrical charge. Positive ions have fewer electrons than
protons and are called cations. Negative ions have more electrons than protons and are
called anions. Add two more electrons to the oxygen atom, draw a diagram, write the
notation, and note any other changes below.
d) Now remove 3 electrons from the negative ion you made.
Count the protons ___________________
Count the electrons __________________
What is the net charge? ______________
e) Suggest a method for calculating the net charge for any atom or ion
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Chemistry I
Matter: Atomic Structure and Bonding
Part 4 – Learn about electron arrangement
4)
Click reset all, and then expand the information windows like you did when
beginning this activity. Build neutral atoms progressively from hydrogen to oxygen.
Do this by adding a proton to change the element and then an electron to keep the
atom neutral. You will need to add neutrons as you go to keep the atom stable. Watch where
the electrons go as they are added.
a) Electrons occupy orbitals that have different levels of energy. The first energy level is the
closest to the nucleus. What is the maximum number of electrons that can occupy the first
energy level? _____________________
b) Which energy level fills up first? ___________________
Part 5 - Practice
5) Click on the game tab. Choose your level of difficulty 1-4 and see how well you have learned
the material.
Part 6 – Extend your knowledge
6) Answer the following questions. You will need a periodic table.
a) How many protons, neutrons and electrons do these neutral atoms have?
33
16
S
52
24
Cr
127
53
I
40
Ca
67
Cu
protons
neutrons
electrons
b) How many protons, neutrons and electrons do these ions have?
35
17
Cl-1
27
13
Al+3
18
8
O-2
24
Mg+2
64
Cu+2
protons
neutrons
electrons
c) Write the symbol and notation for a neutral atom with
12 protons and 14 neutrons
92 protons and 146
neutrons
36 protons 48 neutrons
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Chemistry I
Matter: Atomic Structure and Bonding
d) Write the symbol and notation for a positive ion with
11 protons, 12 neutrons
and 10 electrons
26 protons, 30 neutrons
and 23 electrons
38 protons, 50 neutrons,
and 36 electrons
e) Write the symbol and notation for a negative ion with
7 protons, 7 neutrons, and
10 electrons
16 protons, 18 neutrons
and 18 electrons
35 protons, 45 neutrons
and 36 electrons
f) The first energy level of electrons is filled by ___________ electrons.
The second energy level can hold __________ electrons; the third can hold ___________ electrons
as well.
Electron arrangements are written by specifying the number of electrons in each energy
level separated by a comma. Carbon for example has an electron arrangement of 2,4
i) Study the diagram and explain the 2,4 electron arrangement.
ii) Which neutral atom would have an electron arrangement of 2,8,3?
iii) What would be the electron arrangement of a Li+ ion?
iv) What would be the electron arrangement of a P-3 ion?
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Chemistry I
Matter: Atomic Structure and Bonding
Elements and the periodic table
Symbols of the Elements – The Gold Dust Kid – An Elemental Tale!
The
kid
mounted his trusty
steed, old (B) ____________________. His shooting
(Fe) ____________________ strapped to his side, he headed out
for
the
bright
(Ne) ____________________ and (Ar) ____________________ lights of Sabattus, aiming to rob the Litchfield stage.
There was sure to be a load of precious (Ag) ____________________ aboard, and
____________________ too. Inhaling
a
probably (Au)
deep breath of
(O) ____________________ he coughed on the (S) ____________________ from the nearby mills. Since the (Hg)
____________________ was climbing, he quenched his thirst with some (H2O) ____________________ tasting the (Cl)
____________________ all big cities seem to have. As he headed north his bones ached with (Ca)
____________________ deposits built up over years of riding the (Zn) ____________________ trail. Overhead a
bird soared as if it had (He) ____________________ beneath its wings and the sun beat down like
burning (P) ____________________.
Soon he spotted the stage, guarded by a sheriff with a (Sn)____________________
badge.
“Halt”, he yelled, “or I’ll fill you full of (Pb) ____________________”. The sheriff drew his gun, but alas he was
too slow. The kid’s gun, blazing like (Mg)
____________________, did the (Cu) _________________ in. Anyone
who drew on the kid should know that their life wasn’t worth a plugged (Ni) ____________________.
____________________blonde riding beside the (Al) ____________________
A (Pt)
framed coach, rode for her life
when the kid pulled out some (N) ____________________ compounds, preparing to blow the safe to
atoms.
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Chemistry I
Matter: Atomic Structure and Bonding
Suddenly, a shout rang out, “Hi Ho (Ag)
white horse raced across the (Si)
____________________”, and a masked man on a
___________________ sands like (Na) __________________
skittering on water. A (H) ____________________ bomb would not have stopped the lawman;
the kid had meet his match. The rest of his life was to be spent behind alloyed bars of steel, a warning to
all who flirt with danger. Your first detention may be the initial step in a (C) ___________________ copy life
of the saga of the (Au) __________________ Dust Kid.
* Watch this little rap number to see what scientists are currently getting up to at CERN.
http://www.youtube.com/watch?v=j50ZssEojtM
Write a comment about something that struck you about the science in the song.
How small is an atom? http://htwins.net/scale2/
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Chemistry I
Matter: Atomic Structure and Bonding
“Heavy Water” , D2O
http://www.youtube.com/watch?v=hUVzb0fzHsk - Heavy Water
http://www.youtube.com/watch?v=fyK6kPi8k78 - Can you drink heavy water?
Activity – Isotopes and Average Atomic Mass
Complete the online tutorial from Absorb Learning – posted on Haiku!
Recall: isotopes are atoms of the SAME element that have different numbers of neutrons.
Isotopes all have the SAME atomic number but have different MASS numbers.
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Chemistry I
Matter: Atomic Structure and Bonding
Worksheet – Isotopes
1. The table below gives some information about some atoms. Complete the
missing information on the table.
Atomic
Number
Mass Number
Ionic Charge
1
5
2
+1
0
21
1
Number of
Protons
1
9
Number of
Neutrons
Number of
Electrons
6
1
5
2
10
1
a. Highlight the rows in the table to indicate those atoms that are isotopes of the
same element. Which element is it?
2. The element Gallium has two stable isotopes, Gallium-69 and Gallium-71. About 60%
of the gallium found in nature is 69Ga.
a. What would be the approximate percentage in nature of 71Ga?
b. Estimate (and explain) the average atomic mass of gallium (check your estimate
on the) periodic table
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Chemistry I
Matter: Atomic Structure and Bonding
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Chemistry I
Matter: Atomic Structure and Bonding
Vocabulary Page:
By the end of this topic, you should be able to define and correctly use the following
terms:
Element
Atom
Proton
Neutron
Electron
Nucleus
Bohr-Rutherford
diagram
Electron arrangement
Valence electrons
Ion
Compound
Molecule
Formula Unit
Chemical symbol
Chemical formula
Diatomic molecule
Reactants
Products
Isotope
Atomic number
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Chemistry I
Matter: Atomic Structure and Bonding
Mass number
Average atomic mass
Average formula
mass
Ionization
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Chemistry I
Matter: Atomic Structure and Bonding
Water Chemistry
What are the properties of materials, and what happens to them during
chemical change?
What evidence do we have of chemical change, and what chemical concepts
help us explain that evidence?
Key Scientific Concepts
You should be able to understand, explain and illustrate these ideas:



Substances can be changed chemically into new substances, but matter is not lost, only
rearranged.
There are patterns in chemical reactions that can help us predict what will happen when
two substances react.
Chemical reactions can be described using chemical equations and symbols.
Atoms can gain, lose or even share electrons in order to achieve a full
outer shell and be more stable. The formation of chemical bonds
provides a way for atoms to do this. When atoms bond together,
compounds are formed.
The Guiding Questions
1. How does the arrangement of electrons determine the formation bonds?
2. How do the bonds or forces between particles determine the physical
properties of a compound?
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Chemistry I
Matter: Atomic Structure and Bonding
The Chemistry of Water – Online Tutorial
http://www.absorblearning.com/chemistry/units/LR1101.html
Username:
student15398
Password: hsscience
Click on the “Contents” tab, then scroll
down until you reach “Water”.
Select the first tutorial “Water”
Use the orange forward arrows  to
navigate through the tutorial.
Answer the questions below as you
move through the tutorial.
Water Molecules:
1. Explain why we call water a COMPOUND:
2. How many Oxygen Atoms and Hydrogen Atoms are in one water MOLECULE?
_____________ O atoms
____________ H atoms
3. The FORMULA for water is H2O. The number 2 is called a SUBSCRIPT. It tells you there are TWO
________ atoms in every one water molecule.
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Chemistry I
Matter: Atomic Structure and Bonding
The Hydrogen atoms and the oxygen atom is CHEMICALLY BONDED together
by COVALENT BONDS.
4. How many electrons are needed to complete the outer shell of Hydrogen? ___________
5. How many electrons are needed to complete the outer shell of oxygen? ______________
6. The “X” symbol on the diagram represents ________________________________________
7. The grey dot symbol on the diagram represents ___________________________________
8. Circle the diagram that shows the COVALENT bond between the oxygen atom and
hydrogen atoms. What is SHARED between the atoms?? __________________________
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Chemistry I
Matter: Atomic Structure and Bonding
Chemical Properties of Water – Polarity
9. Based on the diagram, explain what it means for a molecule to be POLAR:
Water’s POLARITY is helpful for explaining many of the special physical and chemical properties of water.
Watch the video of a salt dissolving in water:
http://chemistry.beloit.edu/Water/moviepages/Comp3salt.htm
10. What do you notice about the movement of salt ions and the movement of water moleucles in the
animation?
11. Use this diagram to show why water is such a good SOLVENT for many ionic compounds.
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Chemistry I
Matter: Atomic Structure and Bonding
Bonds are also BETWEEN water molecules – these are called HYDROGEN BONDS.
12. Look at the diagram below. Between which TWO ATOMS does a hydrogen bond form?
13. Look at the structure of ice above. What do you notice about the distance between the water
molecules in ice? What property of ice is a result of this structure?
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Chemistry I
Matter: Atomic Structure and Bonding
More on Covalent Bonding
Some elements exist as “diatomic molecules”, with atoms
forming a covalent bond between them.
How is the octet rule satisfied in a covalent bond?
The Importance of Dissolved Oxygen in Water Systems:
1. Look at the graph below. How does the amount of dissolved oxygen in water vary with
temperature?
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Chemistry I
Matter: Atomic Structure and Bonding
2. Look at the graphic below. Why is the amount of dissolved oxygen in a water
supply important?
Covalent bonds form
between atoms of nonmetallic elements. The
number of bonds that
an atom can form
depends on the number
of valence electrons.
For example, in Cl2 two chlorine atoms are held together by a single covalent bond.
a single covalent bond =
one shared pair of electrons
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Chemistry I
Matter: Atomic Structure and Bonding
Valence electrons and Lewis Dot Diagrams
To understand bonding you must have a very clear idea about valence electrons
Lewis dot diagrams are used to illustrate the number of valence electrons for an atom:
1. Determine the number of valence electrons.
2. Write the element symbol
3. Place one dot to represent electrons around the four sides of the element symbol. Do not place
two electrons together until each side has one (exception is helium).
Use Lewis Dot Diagrams to show the covalent bonding in:
HCl (hydrochloric acid)
and
CH4 (methane)
Multiple Covalent Bonds
Atoms joined by a covalent bond can share more than one pair of electrons. Consider the
bonding in a molecule of O2.
a double covalent bond = two shared pairs of electrons
Draw the Lewis Dot diagram to show the covalent bonding in CO2
:
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Chemistry I
Matter: Atomic Structure and Bonding
a triple covalent bond = three shared pairs of electrons
Draw the Lewis Dot diagram to show the covalent bonding in N2
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Chemistry I
Matter: Atomic Structure and Bonding
More Practice with Covalent Bonding
Covalent bonding occurs when two or more nonmetals share electrons. In this way, the outer
energy level is full at least part of the time. Atoms can share 1, 2 or even 3 pairs of electrons in order to
satisfy the octet rule. Indicate the covalent bonding by circling the shared pair(s) of electrons. The first two are
done for you.
1.
Hydrogen and Chlorine
HCl
H +
2.
Cl
Hydrogen and Oxygen
H +
H Cl
H 2O
O
3.
Nitrogen and Hydrogen
4.
Chlorine and Chlorine
5.
Oxygen and Oxygen
6.
Carbon and Oxygen
7.
Nitrogen and Nitrogen
8.
Hydrogen and Hydrogen
+ H
H O
H
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Chemistry I
Matter: Atomic Structure and Bonding
Naming Covalent Compounds
Since multiple bonds can occur in covalent compounds, a special naming system is required to
indicate how many atoms of each element are in the compound’s chemical formula. Prefixes are
used to indicate these numbers (the subscripts). These prefixes are listed below and are only used with covalent
compounds (no metals)
Prefixes
Mono = one
Di = two
Tri = three
Tetra = four
Penta = five
Hexa = six
Examples
CO2 is named carbon dioxide (mono dropped on carbon)
H2S is named dihydrogen monosulfide
Carbon tetrachloride would have the formula CCl4
Write the formula or name for these binary covalent compounds
1.
NH3
2.
carbon monoxide
3.
SO2
4.
dinitrogen trioxide
5.
CCl4
6.
hydrogen bromide
7.
N2H4
8.
dihydrogen sulfide
9.
N2O4
10. carbon tetrafluoride
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Chemistry I
Matter: Atomic Structure and Bonding
The atoms in elements and compounds can be rearranged by CHEMICAL
reactions and new substances are formed. This involves BOND BREAKING
and BOND FORMING.
What are three signs that a chemical change is occurring?
Using models to
show chemical change:
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Chemistry I
Matter: Atomic Structure and Bonding
www.explorelearning.com
Student Exploration: Chemical Equations
Class Code: ___________________________
Prior Knowledge – Mini Activity (Do these BEFORE using the Gizmo.)
1. Measure 5 ml of 0.1 M lead (II) chloride solution and mass it. Record the mass:
_____________________________ Measure 5 ml of 0.1 M sodium nitrate solution and mass it. Record the
mass: ________________________.
Put a small 50-ml beaker on the electronic balance and tare it. Combine both solutions in the beaker
and record their combined mass of solution: ________________________. What did you observe in the
reaction?
2. Watch the demonstration of an Alka-Seltzer reacting with water while on an electronic balance.
What do you observe happening?
What happened to the mass during the course of the reaction?
Explain what was happening.
What do these two activities tell you about mass changes during chemical reactions?
Gizmo Warm-up
Burning is an example of a chemical reaction. The law of conservation of matter states that no atoms
are created or destroyed in a chemical reaction. Therefore, a balanced chemical equation will show the
same number of each type of atom on each side of the equation.
To set up an equation in the Chemical Equations Gizmo™, type the chemical formulas into the text
boxes of the Gizmo. First, type in “H2+O2” in the Reactants box and “H2O” in the Products box. This
represents the reaction of hydrogen and oxygen gas to form water.
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Chemistry I
Matter: Atomic Structure and Bonding
1. Check that the Visual display is chosen on each side of the Gizmo, and count the
atoms.
A. How many hydrogen atoms are on the Reactants side? ____ Products side? ____
B. How many oxygen atoms are on the Reactants side? ____ Products side? ____
2. Based on what you see, is this equation currently balanced? _________________________
Activity A:
Get the Gizmo ready:
Interpreting
chemical formulas
 Erase the chemical formulas in each text box.
 Check that the Visual displays are selected.
Introduction: To balance a chemical equation, you first need to be able to count how many atoms of
each element are on each side of the equation. In this activity, you will practice counting the atoms that
are represented in chemical formulas.
Question: How do we read chemical formulas?
1. Observe: Type “H2” into the Reactants box and hit Enter on your keyboard. Note that the
formula is shown as H2 below. The small “2” in H2 is a subscript.
A. What does the “2” in H2 represent? _______________________________________
B. In general, what do you think a subscript in a chemical formula tells you? _________
___________________________________________________________________
C. Try typing in other subscripts next to the H, such as 3, 4, and 5. Is your answer to
question B still true? Explain. ____________________________________________
2. Count: Clear the Reactants box, and type in a more complex chemical formula: “Ca(OH)2.”
Look at the number of atoms shown.
A. How many of each type of atom do you see?
Ca: _____
O: _____
H: _____
B. In general, what happens when a subscript is found outside of parentheses?
___________________________________________________________________
C. Try typing in other subscripts next to the (OH), such as 3, 4, and 5. Is your answer to
question B still true? Explain. ____________________________________________
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Chemistry I
Matter: Atomic Structure and Bonding
3. Practice: For each of the real chemical formulas below, calculate how many of
each element there are. Check your answers for the first three formulas using the
Gizmo.
AgCl3Cu2
Ag: _____Cl: _____Cu: _____
Ba(AsO4)2
Ba: _____As: _____O: _____
(NH4)3PO4
N: _____
Activity B:
Balancing
equations
H: _____
P: _____ O: _____
Get the Gizmo ready:
 Erase the chemical formulas in each text box.
Introduction: In a chemical reaction, the reactants are the substances that enter into the
reaction, and the products are the substances that are made in the reaction. A chemical reaction
is balanced if the numbers of reactant atoms match the numbers of product atoms.
Goal: Learn to balance any chemical equation.
1. Observe: To model how hydrogen and oxygen react to make water, type “H2+O2” into the
Reactants box and “H2O” into the Products box.
As the equation is written, which element is not in balance? ________________________
Explain: _________________________________________________________________
2. Balance: To balance a chemical equation, you are not allowed to change the chemical
formulas of the substances involved in the reaction. You are allowed to change the number
of molecules of each substance by adding coefficients in front of the formulas.
A. To balance the oxygen atoms, add a “2” in front of the “H2O” in the Products box.
How many oxygen atoms are found on each side of the equation now? _________
B. To balance the hydrogen atoms, add a “2” in front of the “H2” in the Reactants box.
How many hydrogen atoms are found on each side of the equation now? _________
C. Is this equation currently balanced? _________ Click Show if balanced to check.
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Chemistry I
Matter: Atomic Structure and Bonding
3. Apply: Now enter a more complex chemical reaction: Ca(OH)2 + HBr  CaBr2 +
H2O. List the numbers of each element in the tables below:
Reactants
Ca
O
H
Products
Br
Ca
O
H
Br
A. Which elements are out of balance? ______________________________________
B. Add coefficients to balance first the bromine (Br) and then the hydrogen (H) atoms.
When the equation is balanced, write the complete formula below:
___________________________________________________________________
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Chemistry I
Matter: Atomic Structure and Bonding
Rates of Reaction – How fast do reactions happen?
www.absorblearning.com/chemistry/contents
The idea of RATES is all around us! For example, the speedometer in your car is telling you how
fast you are going in km/h. The flow of water out of your tap could also be a rate measured in
liters/minute.
1. What do these two rates have in common in terms of measuring them?
The ONLY way to determine the rate of a reaction is _____________________________. The balanced
chemical equation doesn’t tell you anything about the rate!
In real experiments, we find some property of the reacting mixture that changes as the reaction
takes place and we measure that. That's easy in reactions that produce a gas as one of the
products – for example, marble chips (containing calcium carbonate) reacting with hydrochloric
acid:
2. Write and balance the chemical equation here:
When a gas is produced, a relativity easy way to measure the rate of reaction is to collect the
gas. The diagrams below show three different ways of doing this.
38
Chemistry I
Matter: Atomic Structure and Bonding
3. What data would you need to collect from each reaction to determine the RATE
of the reaction?
4. What variables would you need to keep constant?
The change in reactant consumption or product
formation over time can be graphed.
4. What can you say about the slope of the line at
the beginning of the reaction:
the middle of the reaction:
the end of the reaction:
5. How is the slope of the line related to the RATE?
6. Buy WHY does this happen? Collision Theory helps explain our observations on rates. The
two main requirements for a reaction are:
a)
b)
39
Chemistry I
Matter: Atomic Structure and Bonding
7. Explain why, based on collision theory, the rate of a reaction changes as the
reaction progresses?
Go Back to the main tutorial page, and click on the next tutorial: The Effect of Surface
Area
1. Completely label the apparatus below. Watch the animation and sketch the resulting graphs.
2. What is the relationship between increasing surface area and the rate of a reaction? Explain
using Collision Theory.
3. What other ways can you increase the surface area of a reactant?
40
Chemistry I
Matter: Atomic Structure and Bonding
Effect of Concentration and Pressure
Concentration in chemistry is expressed as “moles per liter” or “moles per dm3”
(mol dm-3). A mole is ____________________________.
So a solution with a concentration of 2 mol/L will have ___________________ as many particles as a
solution with a concentration of 1 mol/L.
1. Watch the animation of the experiment below, and record your observations. Which has the
faster rate, and why?
1 mol/L
2 mol/L
2. If you tripled the concentration of the acid, what would happen to the rate?
3. For gases, increasing the pressure of a gas is the same as increasing the
_________________________ of an aqueous solution. Explain using Kinetic Molecular Theory.
41
Chemistry I
Matter: Atomic Structure and Bonding
Effect of Temperature
In the reaction below, sodium thiosulfate and hydrochloric acid reacts and a fine
precipitate of sulfur is formed. The reaction and graph are below:
1. Based on the graph, which reaction is faster and how can you tell?
2. Explain using Collision Theory.
3. Why do you think the same amount of sulfur is produced in each reaction?
42
Chemistry I
Matter: Atomic Structure and Bonding
INDEPENDENT RESEARCH PROJECT (IRP) – Rates of Reaction
A research question can simply take the form “How does X affect the rate of a
chemical reaction?” BOTH variables should be measurable by numbers.
Possible X variables:
1. What question do you plan to investigate? Write your Research Question.
2. What is your independent variable (the factor that that you will change to make one treatment
different from another)?
3. What is your dependent variable (what you will be measuring)?
On the x-axis is your independent variable. These are the numbers that you decide in advance, to
create your various manipulations.
43
Chemistry I
Matter: Atomic Structure and Bonding
5. What FIVE manipulations do you plan? This is the range of your independent
variable (Each level of your independent variable is a manipulation or treatment. You
should plan to change only the independent variable from one treatment to the next,
keeping all other conditions constant.)
You should do three trials or replicates will you have for each treatment. (15 data points total!)
6. What factors will you keep constant or fixed for all treatments? (The constants in an experiment
are all the factors that do not change.) These are also called the “controlled variables”.
8. What equipment will you need? You must submit a complete list to your teacher BEFORE the
experiment day!
9. What will you measure, and how will you display your data? Sketch an empty data table here, with
the appropriate headings as well as a diagram of your set-up.
44
Chemistry I
Chemical Reactions and Bonding
Other types of Chemical Bonding Ionic Bonding
BRAINSTORM– Guiding Question 1
How does the arrangement of
electrons determine the formation of ions and
ionic bonds? Write your ideas below.
45
Chemistry I
Chemical Reactions and Bonding
When ionic compounds form, it is electrostatic forces between oppositely charged ions that
hold the compound together. These forces are the ionic bonds.
+
-
ATTRACTIVE
FORCE HOLDS
IONS elements an ionic bond is formed.
When metallic elements react with non-metallic
Metal atoms have a tendency to lose valence electrons and form positive ions.
Non-metals have a tendency to gain valence electrons and form negative ions.
Consider these Rutherford-Bohr diagrams showing the electron arrangements of Mg and Cl
atoms (the details about protons and neutrons have been omitted – remember, bonding is all
about electrons).
46
Chemistry I
Chemical Reactions and Bonding
Now draw Rutherford – Bohr diagrams of the ions that form. Write the electron arrangement for each ion
(in 2,8,8,2 format)
What do you notice about the outer electron shells for the ions you have drawn?
Octet “rule” : when ions form, atoms tend to gain or lose electrons so that the outer valence shell is full
(usually 8 electrons). They do this because the ions formed are at a lower energy state and are more
stable.
When ionic compounds form, the positive and negative ions combine in ratios so that the
overall electrical charge is neutral. This means the amount of positive charge equals (and
cancels out) the negative charge.
Look again at the ions that you drew previously.
Note that
47
Chemistry I
Chemical Reactions and Bonding
o
o
the ions are oppositely charged, and are attracted to each other. THIS IS THE
IONIC BOND!
the overall electrical charge (the sum of the ion charges) is NOT ZERO, this
combination is not neutral
The actual chemical formula for the ionic compound that forms between magnesium and
chlorine is MgCl2. Does this make sense?
The idea of balancing electrical charge is the concept behind writing the chemical formula of
any ionic compound.
Writing chemical formulas for ionic compounds
What is the chemical formula of the compound that forms between calcium and bromine (called calcium
bromide)?
Steps
1. determine the ionic charge of each element (use the Periodic table)
2. cross over the charges (don’t include the positive and negative signs) and simplify if necessary
Practice: Write the chemical formula for the ionic compound magnesium oxide
Need extra review? Check out the GCSE Bitesize link on the class Haiku
Formation of Ions
48
Chemistry I
Chemical Reactions and Bonding
Metals tend to _______________ electrons to form __________________ ions called
________________.
Non-metals tend to ______________ electrons to form ________________ ions called
________________.
State the Octet Rule:
49
Chemistry I
Chemical Reactions and Bonding
Recall that Ionic bonding occurs when a metal transfers one or more electrons to a nonmetal.
The transfer of electrons can be shown using electron dot diagrams. Show the transfer of
electrons in the following combinations. Use the criss-cross rule to check your work by writing
the chemical formula. The first two are done for you:
1.
2.
Na+1Cl-1
Na + Cl
or
x
x
Na +
Cl
[Na]+[[
x
Cl
NaCl
]-
Ca + Cl in this example, Ca loses 2 e- so 2 Cl atoms are required
Cl
3.
Mg + O
4.
Al + N
5.
Li + O
x
x Ca
x
+
Cl
[
x
Cl
]
-
[Ca]+2
[
[
x
Cl
]
-
Ca+2Cl-1
or
CaCl2
Naming Simple Ionic Compounds
We know how to write the chemical formula of a simple ionic compound from its name. We
must also know how to state the name of compound from its formula.
What would be the name of the ionic compound
MgCl2?
50
Chemistry I
Chemical Reactions and Bonding
Calculating Formula Mass
Chemical Reactions Gizmo revisted…
Introduction: Chemists are often interested in obtaining a certain amount of product from a
chemical reaction. But how is this done? To calculate the proportions of reactants needed to
form a desired product, it is necessary to understand a unit of quantity called the mole.
Using data from your periodic table, calculate the formula mass of MgCl2
Calculate the formula mass of H2O
Calculate the formula mass of Pb3N4
Calculate the formula mass of C6H12O6
51
Chemistry I
Chemical Reactions and Bonding
More on Ions!
Some metallic elements can form ions with two or more different charges!
Recall
Metallic elements in group I form +1 ions
Metallic elements in group II form +2 ions
Metallic elements in group III form +3 ions
Iron can form either +2 or +3 ions. Write the two possible formulas for iron oxide below
The naming system used by chemists uses ROMAN NUMERALS to
show the charge on metal ions when more than one possibility could
occur.
Group I, Group II and Group III metals, plus
some others (like Zn and Ag) can only have
one possible ionic charge. Roman numerals are not used in these cases.
Practice: Try writing the names of these
compounds
Practice: Try writing the chemical formulas
of these compounds
BeCl2
sodium sulfide
CuBr2
copper (I)oxide
SnO2
Pb3P2
nickel (III) chloride
iron (III) nitride
52
Structure and Properties of Ionic Compounds
Ionic compounds are crystalline solids. Positive and negative ions arrange themselves in regular geometric patterns.
Most ionic compounds are soluble in water. When added to water, they dissolve to make a solution.
When ions are dissolved in water, they are free to move.
This means the solution will conduct electricity.
Watch the animation of salt dissolving in water.
53
Worksheet: Polyatomic Ions
Polyatomic ions are groups of non-metallic atoms held together by covalent bonds but having an overall positive or negative charge. Polyatomic ions can
form ionic bonds with other ions. Some common polyatomic ions and their names are:
NH4+1
CO3-2
ammonium
carbonate
OH-1
SO4-2
hydroxide
sulfate
NO3-1
PO4-3
nitrate
phosphate
Combine each of the positive ions in the rows below with each negative ion at the top of each column. Write the chemical formula and the name for each
compound.
Cl-1
OH-1
NO3-1
CO3-2
SO4-2
PO4-3
NH4+
Ca+2
Al+3
54
Pb+4

Vocabulary Pages
By the end of this topic, you should be able to define and correctly use the following terms:
Element
Atom
Proton
Neutron
Electron
Nucleus
Bohr-Rutherford
diagram
Electron arrangement
Valence electrons
55
Ion
Compound
Molecule
Formula Unit
Chemical symbol
Chemical formula
Diatomic molecule
Reactants
Products
Isotope
Atomic number
Mass number
Average atomic mass
Average formula
mass
Ionization
56
Activity: Ions in Solution and Precipitation Reactions
Most ionic compounds (salts) in the chemistry lab appear as solid crystals. When these compounds are used in chemical reactions, they are usually
dissolved in water.
The above diagram shows what happens when NaCl (s) is dissolved in water to form Na+ and Cl- ions. The (s) indicates the NaCl is in the solid state. When
added to water, the sodium chloride solution is indicated as NaCl (aq). The (aq) stands for “aqueous” meaning “dissolved in water”.
To recap
NaCl (s)
solute
added to
+
water
solvent
to make
=
NaCl(aq)
a solution
In this activity you will be given a number of ionic compounds that have been dissolved in water to form aqueous solutions. When mixed together, the ions
will remain dissolved in water unless a product forms that is insoluble (does not dissolve). The insoluble product is called a precipitate.
57
What to do with the results
When a solid product is formed, this type of reaction is called a double replacement reaction. A
word equation for a double replacement reaction appears below.
silver nitrate + sodium chloride  silver chloride + sodium nitrate
Write the chemical equation for this reaction by replacing the chemical names with the chemical
formula.
There are two products in this reaction. ONE is the solid that is formed but the other remains
dissolved because the second product is soluble in water. YOU can figure out which one is the
solid by looking at the solutions you used in the activity (they are all soluble or they wouldn’t
have been solutions for you to use). Add (aq) aqueous symbols and the (s) solid symbol to
complete the reaction you wrote above.
Use your powers of deduction to figure out the chemical formula of the solid product for each
reaction where a precipitate was formed. Use Google or another source to check if you are
correct (the compounds you identify are insoluble in water).
Review –
When an ionic salt is dissolved in water, it forms a _________________. In this mixture, the solvent is
the ___________________ the solute is the ____________________. An example of the salt dissolving in
water and breaking into ions can be seen in the chemical equation below:
KCl (s)  K+(aq) + Cl-(aq)
How can you tell that the salt has been dissolved in water?
How can you tell that the salt is ionic?
58
A Big Review: Formula Writing and Naming
Write the chemical formula or name for each of the following
1.
CaCl2
2.
sodium oxide
3.
(NH4)2O
4.
calcium nitrate
5.
Na3PO4
6.
dinitrogen trioxide
7.
CuCl2
8.
copper I sulfate
9.
Fe(OH)3
10. aluminum fluoride
Comparing Physical Properties
Physical
Property
Ionic
Crystal
Melting and boiling points
Very high temperatures
Strong attractions between ions
Solubility in water
Most ionic compounds are
soluble in water.
Conduct electricity
Yes when dissolved in water or
melted
Hardness
Very brittle
Structure
Solids with geometrical
arrangement of ions
Covalent
Molecular
Lab Activity – Ionic or Covalent?
In this activity you will be identifying and comparing properties of ionic and covalent compounds
in order to classify 4 unknown substances. The “big” question “how does the bonding involved in
a compound influence the physical properties that can be observed?”
Background Information
Please read the following definitions:
1) Solubility
When we talk about the mixing of two or more substances together in solution we must
consider solubility. Solubility is a measure of how much one substance (the solute) will
dissolve into another (the solvent). Not all substances will dissolve in all solvents.
Understanding solubility properties will provide a basis for understanding the golden rule of
solubility...Like dissolves like!
59
2) Ionic Bond
An ionic bond is an electrical attraction between two oppositely charged atoms.
3) Covalent Bond
Covalent bonds are formed as a result of the sharing of one or more pairs of bonding
electrons.
4) Conductivity
This is a measure of a materials ability to conduct an electric current. Conductivity has SI
units of siemens per meter (S·m-1). Any substance composed of electrically charged
particles (like ions) that are free to move are good conductors of electricity.
Procedure:
Testing melting point
Approximate melting points of substances can be determined rather easily. Watch the
demonstration and pay attention to safety!
Substances with low melting points, less than 100 C, will melt readily when warmed gently in a
small test tube. A small sample the size of a pea will work well.
If the sample melts between 100 C and 300 C, it will take more than gentle warming, but will
melt before the test tube imparts a yellow-orange color to the flame.
Above 300 C, there will be increasing yellow-orange color of the flame up to about 500 C. After
that point, around 550 C, the Pyrex tube will begin to soften.
In this experiment, we will not attempt to measure any melting points above 500 C. Do not
continue heating once the strong yellow-orange color appears!
1.
Test Sample A and Sample B.
2.
Add a small sample of one of your compounds to a dry test tube. Using the proper
technique for heating substances in a test tube, heat your sample gently over a bunsen
burner. If the substance melts, do not continue heating!
3.
Estimate the melting temperature (either <100 C, between 300 C and 500 C, or >500 C)
and record in your data table.
4.
Repeat with your second sample in a new dry test tube.
Testing solubility and conductivity
1.
Using a new sample of each substance, add a small amount of solid to a new dry test tube.
60
2.
Add enough distilled water to fill the test tube halfway. Do not use tap water! Using a
stopper, invert the contents of the test tube repeatedly.
3.
Record whether the solid dissolves in water in your data table.
4.
Use a conductivity tester to test for conductivity.
Volatility
Carefully smell each compound. If you can detect an odor, assume that the compound has a high
volatility. Record as high or low volatility.
Finishing the experiment
1.
Clean up your test tubes and lab stations.
Data Table:
Melting Point
Range
(degrees
Celsius)
Solubility in
Water
(soluble or
insoluble)
Conductivity
(conductive or
non-conductive)
Volatility
(high or low
volatility)
Type of
Bonding in
the Sample
Sample A
Sample B
Sample C
Sample D
Conclusion:
Classify each substance as ionic or covalent and provide an explanation for your
reasoning.
61
"Alchemist's Gold" - Metallic Bonds and Brass
Theory
Prior to the times of Lavoissier, in the 1700’s, chemists who were known as alchemists - spent most of their time
looking for a way to turn matter into gold. Alchemists
spent years developing techniques and trickery that made
their audiences believe that they had the ability of turning
lead (and other substances called "base metals") into
gold. One such trick involved filling a bored-out metal
stirring rod with gold dust. The tip of the rod was then
sealed with wax in order to contain the dust and to keep it
from being seen by others. To prove himself as a master
alchemist the charlatan would stir a heated, empty crucible with this rod and (as the wax melted)
the vessel would slowly fill with molten gold. Although alchemists were measured by the
“success” of their trickery, their less-than-systematic research played an important contribution to
laying the foundation for chemists like Lavoissier and others to build on. It was the alchemists
that discovered and developed the various techniques of chemical purification such as fractional
distillation and sublimation.
When our penny is heated in a solution of sodium hydroxide in the presence of zinc powder,
atoms of zinc which have turned into ions in solution, migrate towards the penny and deposit a
coating of zinc onto the copper. This process is known as wet-chemical plating, as opposed to
electrochemical plating. The coating of zinc gives the penny an appearance of silver. If the
“silver” penny is heated gently the zinc on the surface mixes with the outer layers of copper atoms
of the penny, producing an alloy which looks like gold. In making this alloy, the atoms must
actually exchange places to mix - this is accomplished by adding heat to cause the natural
vibrational motion of the copper and zinc atoms to turn in to fluid motion. The atoms then flow
into each others' "territory."
Materials:
Copper pennies (1981 or before preferred;
metal tongs
Canadian is fine)
hot plate
6 M NaOH. (approx. 100 mL) and zinc
Bunsen burner
(powder or granular, 5 g)
soft cloth
400 mL ceramic evaporating dish
iron wool
250 mL beaker (2)
dilute HCl solution
glass stirring rod
* Sodium hydroxide solutions are corrosive, and skin burns are possible. Heat the NaOH carefully,
to prevent spattering.
* Zinc solutions are irritating to the skin and cause itchy rashes.
* HCl solutions (hydrochloric acid) are corrosive and especially irritating to the eyes and mucous
membranes
62
Procedure
1.
2.
3.
4.
Pour NaOH solution into a ceramic evaporating dish. Add 5 g zinc powder to the
solution and heat slowly. (This solution may be pre-mixed.)
While the zinc solution is heating, dip a penny in dilute HCl, rinse in tap water, and scrub
shiny with iron wool. Repeat until you have a shiny clean penny with a consistent surface.
Place the penny into the zinc/sodium hydroxide mixture. Stir the contents of the dish
while continuing to heat, until the penny develops a silver appearance. Remove the
penny with metallic tongs and dip it in cool water a few times to wash off any adhering
solution. The penny may be dried and polished with a soft cloth.
Use tongs to pass one of the silver pennies back and forth through the flame of a Bunsen
burner. As the penny is heated it will develop the appearance of gold.
Questions
1. What is an alloy?
2. What two metals compose the alloy brass?
3. Why do you think heat is needed to cause the zinc coating to diffuse into the copper?
4. Look in your textbook or other resource for a description of “metallic bonding”. Where are the
electrons in a metallic bond? What two metals are bonded in your brass penny?
63
Chemistry I: Measurement Skills and Uncertainty
Science is a quantitative subject. This means taking measurements and dealing with numbers.


All measurements consist of two parts: the magnitude of the measurement (the number)
and the unit of the measurement.
Measurements are never exact. In other words, measurements always contain a degree
of uncertainty.
Measuring length using: ________________________________________
Measure volume using: ________________________________________
Measure temperature using: ____________________________________
Measure position/velocity using: ________________________________
Measure mass using: __________________________________________
Making measurements
How long is the pencil?
2
3
4
5
cm
When making measurements in science, the last digit of the measurement is estimated. This
digit is called the uncertain digit (because it is an estimate).
When taking a measurement:
 read the scale to the smallest graduation (the limit of measurement)
 estimate the last digit by reading between the last two marks on the scale!
This produces a more precise measurement but with a degree of uncertainty. A good rule of
thumb is that the uncertainty in a measurement is equal to half of the smallest graduation
on the measurement scale.
Practice
Indicate the lengths of the objects shown in these pictures. Include uncertainty and units in your
measurements.
Diameter of penny
Length of pencil
64
Now use your own ruler to …
a) Measure the height of this diagram of Fluffy the Chemistry Cow
E=mc2
?
Significant Figures (Digits)


Significant figures in a measurement include all the digits that are known for “certain”
plus one more “uncertain” digit
More precise instruments mean your measurements will have more significant figures
(and smaller uncertainties)
How many significant figures are in a measurement?
In any given measurement, all non-zero digits (1 to 9) are always counted as significant. There are
special rules for zeros when counting significant figures.
Rule
Zeros between non-zero digits are significant.
Zeros following a non-zero digit and after a
decimal are significant.
Zeros before the first non-zero digit are not
significant. A single zero used as a place
marker before the decimal is NOT significant.
Zeros at the end of a number that does not
have a decimal are not significant.
Examples
40.5 has 3 S.F.
2001 has 4 S.F.
5.230 has 4 S.F.
1.00 has 3 S.F.
0.000450 has 3 S.F.
0.5 has 1 S.F.
100 has 1 S.F.
4010 has 3 S.F.
65
Practice Worksheet – Significant Figures
How many significant figures are there in each measurement?
a) 727.2 m
b) 601 g
c) 46.0 mL
d) 0.044 g
e) 320 cm
f) 0.00401 L
g) 1060 s
h) 123456 mg
i)12.500 g
j)340.010 mL
k) 0.02 m
l)0.5 kg
m)
n) 8.00  108 m
o) 6.80 C
p) 7.67  101 C
1.113  103 kg
2. After a calculation, you may need to round off the result to a certain number of significant
figures. Round off these results to the number of significant figures listed. The first one is
done for you.
a.
654.64587 m to 6 SF = 654.646 m
d. 100 cm to 3 SF
b. 654.64587 m to 3 SF
e.
c.
7000 cm to 2 SF
654.64587 m to 1 SF
This produces a more precise measurement but with a degree of uncertainty. The
degree of uncertainty is at a minimum equal to half of the smallest
graduation on the measurement scale.
Estimating Uncertainty
In all science labs this year, you will never make a measurement without
including an uncertainty. How you choose that uncertainty will depend on what
the measurement tool was and how it was used. The uncertainty included will have
to be reasonable. This will take practice and judgement.
66
Chemistry I
In Search of Solutions: Water
Chemistry Topic 1 Matter: Atomic Structure and Bonding
Practice – Estimating Uncertainty
Make measurements for each of the situations shown in the diagrams. Include uncertainty
with each measurement.
Example 1. Measure the volume in each of the three
pipettes shown.
From left to right:
Pipette 1 : 5.74  0.05 mL
Pipette 2 : 3.0  0.3 mL
Pipette 3 : 0.34  0.02 mL
All are acceptable measurements. Try these!
Beaker 1
Beaker 2
Cylinder 1
Measure the following:
Pay attention to precision and uncertainty!
Measurement
Equipment used to measure
and uncertainty
Volume of water a test tube can hold:
______________
Mass of five paper clips: _______________
Temperature of a beaker of water:
______________________
67
Chemistry I
In Search of Solutions: Water
Chemistry Topic 1 Matter: Atomic Structure and Bonding
Distance between pillars in the quad:
____________________
Length of a piece of A4 paper:
_________________________
Volume of my coffee cup:
__________________________
Cylinder 2
Cylinder 3
Cylinder 5
Cylinder 6
Cylinder 4
68
Chemistry I
In Search of Solutions: Water
Chemistry Topic 1 Matter: Atomic Structure and Bonding
Example 2. What is the diameter of this penny?
Answer: 1.92  0.05 cm
This is not a realistic measurement because the nice
lines shown in the picture do not exist in the lab. If I
made this measurement for real, the result would
probably be more like 1.9  0.1 cm.
More practice! Make measurements using the diagrams shown below.
Temperature 1
Length 1 (scale in cm)
Voltage 1
Length 2
Mass 1
Length 3 (scale in cm)
69
Chemistry I
In Search of Solutions: Water
Chemistry Topic 1 Matter: Atomic Structure and Bonding
Length 4 (scale in cm)
3.0


Length 5 (scale in cm)
Precision and Accuracy
Good science involves measuring a physical quantity a number of times.
We often use the terms precision and accuracy interchangeably when
they mean very different things. Remember this when writing lab
reports.
Accuracy is an indication of how close a measurement is to the accepted
value.
Precision is an indication of the agreement among a number of
measurements made in the same way.
Practice Exercise 3.0
Consider the following table of results for 4 students who are trying to
measure “g”, the acceleration of a falling object due to gravity.
Trial
1
2
3
Mean
Bob
Joe
Sue
Kate
7.83
11.61
8.85
9.43
9.53
9.38
8.87
9.26
8.70
8.75
8.77
8.74
9.72
9.86
9.70
9.76
The accepted value for “g” is 9.81 ms-2.
Compare the accuracy and precision of each student.
70
Chemistry I
In Search of Solutions: Water
Chemistry Topic 1 Matter: Atomic Structure and Bonding
Whose results are meaningful, and whose results are questionable?
Solutions and Concentration: What’s the Concentration of Iced Tea?
Adapted From Amy Rosen, Manhattan International High School
Introduction:
The CONCENTRATION of a solution tells you HOW MUCH of a substance is dissolved in a certain amount of
solvent. The solvent for an aqueous solution is __________________________.
Concentration can be shown in a variety of ways:
As a percentage….in a 5% (read ‘five percent’) salt solution…there are 5 parts for every 100 parts…or 5 grams
for every 100 grams…or 5 ml for every 100 ml…
As mass per volume…in a 10 g/L (read ‘ten grams per liter’) solution
As Molarity…a 1 M (read ‘one Molar) solution…it’s equal to the molecular mass of the compound per liter of
solution. In Chemistry, Molarity is the most common way of expressing concentration BUT in Grade 9, the
mathematics of a mole and molarity are better left for next year!
Purpose: To Make three solutions of iced-tea with different concentrations and taste them to decide which is the
‘best’ concentration for your taste! To mathematically compare solution concentration.
You will prepare 100.0 ml of each of the following Iced Tea solutions:
A) 100 g/L
B) 50 g/L
C) 10 g/L
71
Chemistry I
In Search of Solutions: Water
Chemistry Topic 1 Matter: Atomic Structure and Bonding
Materials:
Iced Tea Powder
Drinking Water
plastic spoons
electronic Balance
Plastic cups
Ruler
Procedure:
1.
Calculate how much solid drink crystals you will need to make 100 ml of each solution. Show all of your
calculations below.
Mass of drink crystals needed for 100 ml of a 100 g/L solution:
Mass of drink crystals needed for 100 ml of a 50 g/L solution:
2. Using a graduated cylinder, measure 100.0 ml of water, and pour it into a plastic cup, then draw a line to show
the level of the water in the other cups. (Usually we would use more accurate measuring techniques, but we
can’t drink out of lab equipment.)
3. Make your solutions of iced tea! Mass out the iced tea crystals first, then add enough water to the line to make
a 100.0 ml solution.
4. Observe and taste the solutions you have made. You can have one “designated taster” or you can pour a little
into separate cups for each group member to taste. Record how each solution looked, smelled, and tasted.
5. Making a Solution by DILUTION:
Now make a 10 g/L solution by using either the 100g/L or the 50 g/L solution! You will make this ONLY BY
DILUTING the solution! How will you do this? (hint: calculate how many times more concentrated a 100g/L
solution is than compared to a 10g/L solution…Describe what you will do below, then make it and taste it!
6. Compare the solutions, and decide which one is closest to the ‘perfect taste’ concentration? If you have extra
time, you can try to make one more solution with the exactly perfect concentration based upon your
observations.
Observations:
Concentrations
10 g/L
Observations
50 g/L
100 g/L
Questions:
1. Which concentration that you tested was your ‘ideal’ concentration of iced tea?
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Chemistry I
In Search of Solutions: Water
Chemistry Topic 1 Matter: Atomic Structure and Bonding
2. The ‘threshold’ of sweetness people can taste has actually been measured and is about 62 g/L. How did yours
compare? 
3. It would have been mathematically easier for you to make 1 L solutions (you would have just had to mass the
100 g, for example). Explain why we didn’t do this and only made 100 ml of solutions instead.
4. How many times more concentrated was the 100g/L solution than the 10 g/L solution?
5. How many times more concentrated was the 100g/L solution than the 50 g/L solution?
6. How many times more concentrated was the 50g/L solution than the 10 g/L solution?
7. How many times less concentrated was the 10g/L solution than the 100 g/L solution?
Separation of Leaf Pigments by Paper Chromatography
The pigments involved in photosynthesis can be separated and identified by paper chromatography. Various
pigments have different solubilities in the solvent with the result that as the solvent (ethanol) ascends the
absorptive paper it carries the pigments with it at different rates. In this way they become separated from one
another and can be identified by their different colors and positions.
Procedure
1. Obtain a strip of chromatography paper of sufficient length to reach almost to the bottom of a large test
tube and of such width that the edges do not touch the sides of the tube.
2. Rule a pale pencil line across one end of the strip approximately 30 mm from the bottom end.
3. Place the paper into the test tube; mark the test tube at the level of the pencil line.
4. Remove the paper and fill the tube with developer to the level of the mark you made. Place a stopper
onto the test tube.
5. Place your leaf onto the paper strip and roll a coin, 15-20 times, with force, to create a dark green line of
pigments about 15 mm above the pencil line.
6. Place the paper into the test tube and replace the stopper.
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Chemistry I
In Search of Solutions: Water
Chemistry Topic 1 Matter: Atomic Structure and Bonding
7.
8.
9.
Watch the setup as the developer rises on the paper strip.
When the developer reaches about 10 mm from the top of the strip, open the apparatus, remove the
strip, and *MARK* the line showing the highest point reached by the developer.
Your chromatogram is now complete and you can proceed to identify the pigments. If you are LUCKY
you should be able to detect the five pigments listed in the table below. They can be identified by their
colors and Rf values.
Name
Carotene
Phaeophytin
Xanthophyll
Chlorophyll a
Chlorophyll b
Color
Yellow
Yellow-Grey
Yellow-Brown
Blue-Green
Green
Rf
0.95
0.83
0.71
0.65
0.45
Analysis
Calculate the Rf of your pigments using this formula:
Rf = Distance pigment moves (mm) / Distance developer moves (mm)
Calculate your Rf and % Error and place into this table:
Name
Color
Rf
My Rf
My % error
Carotene
Yellow
0.95
Phaeophytin
Yellow-Grey
0.83
Xanthophyll
Yellow-Brown
0.71
Chlorophyll a
Blue-Green
0.65
Chlorophyll b
Green
0.45
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Chemistry I
In Search of Solutions: Water
Chemistry Topic 1 Matter: Atomic Structure and Bonding
Filtration and Water Treatment
Phosphates in living organisms
All living organisms require phosphate to make two of the most important organic
macro-molecules: deoxyribonucleic acid (DNA) and adenosine triphosphate (ATP)
The importance of phosphates make them an essential nutrient. Animals easily meet their
phosphate needs by eating other living things. Plants, on the other hand, must absorb
phosphate from the ground and often have difficulty getting enough. To make up this
deficiency, most fertilizers, whether for house plants or commercial crops, include phosphate.
When humans add extra phosphorous to water, they create a condition called eutrophication
that can wipe out aquatic ecosystems.
Eutrophication is characterized by a rapid growth in the plant population (an algal bloom).
With more living plants comes more dead plants needing decomposition. The bacteria that
decompose the dead plants use oxygen, and eventually burn up so much that not enough
remains to support fish, insects, mussels, and other animals, leading to a massive die-off.
The presence of phosphates in virtually every detergent, including household cleaners
and laundry soap, used to contribute significantly to eutrophication
Phosphates can be removed by water treatment plants by reacting waste water with
aluminum ions:
Al 3+ (aq) + PO4 3- (aq)  AlPO4 (s)
What is the significance of the change of state in the above equation? How can we use this
information to remove the phosphates from water?
Your Turn: Add a source of aluminum ions to a sample of waste water that contains
phosphates. (how much of each should you add? What would be reasonable?)
Filter the precipitate…..what does the term ‘precipitate’ mean? Make your observations.
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Chemistry I
In Search of Solutions: Water
Chemistry Topic 1 Matter: Atomic Structure and Bonding
How can the technique of filtration be used to separate pollutants in water? Will filtration
work for all pollutants? Which ones would it work best for?
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