Download 2 - Partnership for Effective Science Teaching and Learning

Matter
PESTL Content Course
Brett D. Moulding – Instructor
November 8, 2008
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Matter = An Overview
Atomic Theory
Conservation of Mass
Chemical Equations
What is a “Mole”
Chemical and Physical Change
Putting it all Together
We will be learning chemistry today
1. Chemistry is not easy – remember some important
things as we work to understand chemistry.
a) Learning is about making sense of things and
connecting it to what we already know of the
natural world.
b) Big ideas should have examples tied to them.
c) We are in this together, we will build upon our
collective experiences and develop new
understanding.
d) Learning is half the fun of living!
A good teacher must be able to put himself in the place
of those who find learning hard.—Eliphas Levi
Matter an Overview
1. Classic Definition – Matter has mass and takes up
space.
a) So what is the difference between mass and
weight?
b) Is matter everything?
c) What affects matter?
i. Energy (e.g., heat, light)
ii. Pressure
iii. Interaction with other matter
d) Matter Cycles
Atomic Theory
Five main points of Dalton's Atomic Theory
1. Elements are made of tiny particles called atoms.
2. All atoms of a given element are identical.
3. The atoms of a given element are different from those of any
other element; the atoms of different elements can be
distinguished from one another by their respective relative
weights.
4. Atoms of one element can combine with atoms of other
elements to form chemical compounds; a given compound
always has the same relative number of isotopes.
5. Atoms cannot be created, divided into smaller particles, nor
destroyed in the chemical process; a chemical reaction simply
changes the way atoms are grouped together.
Making Sense of Matter
MATTER
Substances
ELEMENTS
COMPOUNDS
Mixtures
Solutions
Suspensions &
Mixtures
Atoms
Molecules
Elements and Compounds
Atoms
Atoms
Atoms and/or Molecules
Protons
Protons
Protons
Protons
Neutrons
Neutrons
Neutrons
Neutrons
Electrons
Electrons
Electrons
Electrons
Atomic Theory
Particles
• Matter is made up of particles
• Identity of atoms - Elements
• Conservation of Atoms
• Interaction of Atoms
Space between particles
Periodic Table of the Elements
• Elements
• Atomic Number
• Identity
• Patterns
Periodic Table of the Elements
How to use the Periodic Table
 Elements are described on the periodic table.
 The number of protons in an atom defines the
element.
 For example, carbon atoms have six protons,
hydrogen atoms have one, and oxygen atoms
have eight. The number of protons in an atom
is referred to as the atomic number of that
element. The number of protons in an atom
also determines the chemical behavior of the
element.
http://periodic.lanl.gov/default.htm
Periodic Table of the Elements online
Atomic Symbol
The international atomic symbol is one or two letters chosen to
represent an element (“C" for carbon, “Fe” for iron). Sometimes the
symbol represents the Latin name of the element.
Fe = iron = Ferrous, Sn = tin = Stannous
Atomic Mass
The atomic mass is the average mass of an element in atomic mass
units ("amu").
This is equal to the mass of 6.02 X 1023 particles of the element.
This is referred to as a mole of the element.
Interesting sidebar
Isotopes can have a weight either more or less than the
average. The average number of neutrons for an element can be
found by subtracting the number of protons (atomic number) from
the atomic mass.
Atomic Symbol
6
C
Atomic Number
12.01
Mass Number
Conservation of Matter
1. “In an ordinary chemical reaction matter is
neither created nor destroyed.
2. Conservation of mass and identity of elements
3. Experiments
a) Rusting Nail
b) Cream and Vinegar
Chemical Equations
1. Chemical equations represent a chemical
reaction.
2. The equation indicates the chemical change.
3. The equation indicates the mass is conserved
when balanced.
4. The equation may include energy changes.
Equations
Atoms and/or Molecules
=
Atoms and/or Molecules
H2
Ag+
O2
Cl-
=
=
H2 O
AgCl
CO2
H2 O
=
C6H12O6
O2
How molecules are symbolized
Cl2
2Cl2
• Molecules may also have brackets to indicate numbers of
atoms e.g., Ca(OH)2
H
O Ca O
• Notice that the OH is a group
• The 2 refers to both H and O
• How many of each atom are in the following?
a) NaOH
b) Ca(OH)2
c) 3Ca(OH)2 Na = 1, O = 1, H = 1
Ca = 1, O = 2, H = 2
Ca = 3, O = 6, H = 6
H
Balancing Equations: MgO
• The law of conservation of mass states that matter can
neither be created nor destroyed.
• So we are just moving the furniture in a chemical
reaction
• The number of a particular atom is the same on both
sides of the chemical equation
Example: Magnesium + Oxygen
Mg + O2  MgO
Mg + O O  Mg O
However, this is not balanced
Left:
Mg = 1, O = 2
Right:
Mg = 1, O = 1
Balance equations by “inspection”
From
Mg
2Mg
Mg
Mg2
4Mg
+ O2
+ O2
+ ½O2
+ O2
+ 2O2
 MgO
 2MgO
 MgO
 2 MgO
 4 MgO
is correct
is incorrect
is incorrect
is incorrect
Hints: start with elements that occur in one compound on each side. Treat
polyatomic ions that repeat as if they were a single entity.
a) P4 +5 O2  P4O10
b) 2 Li + 2 H2O  H2 + 2LiOH
c) 2 Bi(NO3)3 + 3 K2S  Bi2S3 + 6 KNO3
Here are some more to balance:
a)
KNO3  KNO2 +
b)
Pb(NO3)2 
c)
P4 +
d)
MgO + H3PO4  Mg3(PO4)2 +
e)
Br2 + KI 
f)
Ca(OH)2 + HNO3  Ca(NO3)2 +
I2 
O2
PbO + NO2 +
O2
PI3
H 2O
I2 + KBr
H 2O
Balanced
a)
b)
c)
d)
e)
f)
2KNO3  2KNO2 + O2
2Pb(NO3)2  2PbO + 4NO2 + O2
P4 + 6I2  4PI3
3MgO + 2H3PO4  Mg3(PO4)2 + 3H2O
Br2 + 2KI  I2 + 2KBr
Ca(OH)2 + 2HNO3  Ca(NO3)2 + 2H2O
What is a “Mole”
A dozen = 12 of anything
Dozen is a way of counting things in bunches
2 dozen eggs, 1 dozen donuts, or 3 dozen golf balls
• 1 dozen eggs has a mass
• 1 dozen golf balls has a mass
• 1 dozen donuts has a mass
A gross of pencils = 144 sheets
A ream of paper = 500 sheets
A mole = 6.02 X 1023 of anything
Mole is a way of counting very small things in groups
• 1 mole of carbon has a mass of 12.01 grams
• 1 mole of hydrogen has a mass of 1.01 grams
• 1 mole of oxygen has a mass of 16.0 grams
• 1 mole of water (H20) has a mass of 18.0 grams
What is a “Mole”
Lets do some math
• 1 ml of water = 1 gram of water
• 1 mole of water = 18.0 grams of water
• 1 mole = 6.02 X 1023 particles
•So, how many molecules of water in a bottle of water?
• Bottle of water = 591 ml of water.
•591 ml H2O X 1 gram H2O X 1 mole H2O
X 6.02X1023 molecules H2O =
1 ml H2O
18.0 grams H2O
1 mole H2O
So we have 2.0 X 1025 molecules in a bottle of water
250.000,000,000,000,000,000,000,000 molecules of water in a bottle of water.
Chemical and Physical Change
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Chemical Properties
Physical Properties
Physical Change
Chemical Change
How do we know when a chemical change has
occurred?
Determine whether the following are chemical or physical changes
a. Tear a piece of paper
(physical)
b. Strike a match
(chemical)
c. Mix a small amount of salt with H2O
(physical)
d. Fold aluminum foil to make a small pan and do the following in
the pan:
i. Put a drop of H2O in the pan.
(physical)
ii. Put a small amount of sugar in the pan and heat it.
(chemical)
e. Add a small amount of vinegar to baking soda
(chemical)
f. Put a small amount of cornstarch in your hand and add a few
drops of H2O to form a dough
(chemical)
Activity
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Place two shiny nails in a small Ziploc snack bag
Add about 20 ml of vinegar
Let both stand in the vinegar for 15-30 seconds
Remove one of the nails and place in a dry Ziploc
snack bag
Observe regularly over the next two days
Compare the appearance of the two nails
Describe your observations and make warranted
inferences and hypothesizes based on evidence
Predict what would happen if you used a galvanized
nail
Preventing a chemical reaction
a. Obtain 2 large nails. Paint one nail and leave the other one
unpainted.
b. Put both nails in a jar with water. Cover the jar and let it
stand 3 days.
c. Compare the appearance of the nails (painted nail does not
form rust).
Can you think of other examples of how we stop or slow chemical
reactions?
Remove energy – Place in a refrigerator, take away sunlight
Take away the source of reactants – Prevent oxygen from
getting to the nail and letting it rust
Replace one reaction with another – Zinc bar on a bridge or
ship will prevent rusting
Chemical and Physical Properties
Qualitative Physical Property
A description of a properties of a substance that is not related to the
amount of the substance present (e.g., density, color, texture). These
are the intensive properties.
Quantitative Physical Property:
A numerical description of a substance specifically related to the amount
of substance (e.g., mass, length). These are the extensive properties.
Chemical property:
A characteristic behaviour which occurs when one substance interacts
with another substance to become a NEW substance.
Chemical Property
A chemical property is any of a material's properties that becomes
evident during a chemical reaction; that is, any quality that can be
established only by changing a substance's chemical identity.
Simply speaking, chemical properties cannot be determined just by
viewing or touching the substance; the substance's internal
structure must be affected for its chemical properties to be
investigated.
Chemical properties can be contrasted with physical properties, which
can be discerned without changing the substance's structure.
Examples of Chemical Properties
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Electronegativity
Ionization potential
pH balance
Reactivity against other chemical substances
Heat of combustion
Enthalpy of formation
Toxicity
Chemical stability in a given environment
Flammability
Preferred oxidation state(s)
Coordination number
Capability to undergo a certain set of transformations e.g.,
molecular dissociation, chemical combination, redox reactions
under certain physical conditions in the presence of another
chemical substance
Preferred types of bonds to form, e.g., metallic, ionic, covalent
Physical Properties
A physical property is any aspect of an object or substance that can be
measured or perceived without changing its identity. Physical
properties can be intensive or extensive. An intensive property does
not depend on the size or amount of matter in the object, while an
extensive property does. In addition to extensiveness, properties
can also be either isotropic, if their values do not depend on the
direction of observation, or anisotropic otherwise. Physical
properties are referred to as observables. It is not a modal
property. Examples of physical properties are sublimation, odor,
color, and shape.
Often, it is difficult to determine whether a given property is physical
or chemical. Color, for example, can be "seen”; however, what we
perceive as color is really an interpretation of the reflective
properties of a surface. In this sense, many ostensibly physical
properties are termed as supervenient. A supervenient property is
one which is actual (for dependence on the reflective properties of a
surface is not simply imagined), but is secondary to some underlying
reality.
Examples of Physical Properties
The physical properties of an object include:
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absorption
acceleration
angle
area
capacitance
concentration
conductance
density
dielectric
displacement
ductility
distribution
efficacy
electric charge
electric current
electric field
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electric potential
emission
energy
expansion
exposure
flow rate
fluidity
frequency
force
gravitation
impedance
inductance
intensity
irradiance
length
location
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luminance
magnetic field
magnetic flux
mass
molality
moment
momentum
permeability
permittivity
power
pressure
radiance
solubility
luster
resistance
spin
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strength
temperature
tension
thermal
transfer
time
velocity
viscosity
volume
Physical Change
A physical change alters only the form or state of the
substance. The chemical composition of the substance has not
changed.
Example:
Melting ice or the evaporation of water. The water still has
the same chemical compositions (H2O) regardless of its state.
Other Examples:
Chemical Change
A chemical change causes substances (the reactants) to change into
different substances (the products).
The products will have different physical and chemical properties than
the reactants.
Examples: rusting nail. Rust has a different composition than nail and different
properties – (Iron Oxide cannot be picked up by a magnet, Iron metal can be
picked up by a magnet
Chemical Reaction
The process of chemical change is called a chemical reaction.
Reactants
Products
Evidence that a chemical reaction has occurred includes:
- Color change
- New solid formed (precipitate)
- New gas formed
- Light produced
-Heat released or absorbed
If the product exhibits one or more of these features a chemical
change likely happened.
Chemical Change –vs- Physical Change
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Chemical change = Chemical reaction
A chemical change is a dissociation, recombination, or rearrangement of
atoms.
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Physical change = A change which does not transform one substance into
another. For example, freezing water is a physical change because both
water and ice are H2O. However, electrolysis of water would not be a
physical change because passing a strong electric current through water
can decompose it into H2 and O2.
Reaction Types and Examples
Synthesis- heat 0.5g Fe filings and 0.5g Sulfur
Fe + S --> FeS
DecompositionBurn some sugar in a test tube
C12H22O11 -->12C + 11H2O
Single replacement- Cover a piece of copper wire with
silver nitrate solution.
Cu + AgNO3 --> CuNO3 + Ag
Double replacementAdd several drops of silver nitrate solution to salt
water.(white ppt, AgCl, forms)
NaCl + AgNO3-->AgCl + NaNO3
Putting it all Together
PC & CC
1. What does this all mean?
2. How do we know when to end the story?
3. Looking for these changes around us.
What is Important Knowledge
• Identify three essential concepts/skills
that you want students to know and be
able to do.
(write them down)
• Select one – circle
• What evidence would you accept that
your students know or can do _____?
Chemistry in a Nutshell
• The Atom
All macroscopic matter is made out of many tiny particles called
atoms. The study of how these atoms interact is called Chemistry.
• Subatomic Particles
The three particles that make up atoms are protons, neutrons, and
electrons. Protons and neutrons are heavier than electrons and reside in
the "nucleus," which is the center of the atom. Protons have a positive
electrical charge, and neutrons have no electrical charge. Electrons are
extremely lightweight and are negatively charged. They exist in a cloud
that surrounds the atom. The electron cloud has a radius 10,000 times
greater than the nucleus.
• The Nucleus
The nucleus of an atom is made up of protons and neutrons in a
cluster. Virtually all the mass of an atom resides in the nucleus. The
nucleus is held together by the tight pull of what is known to chemists and
physicists as the "strong force." This force between the protons and
neutrons overcomes the repulsive electrical force that would, according to
the rules of electricity, push the protons apart otherwise.
Chemistry in a Nutshell (continued)
• Electrons
The electron is the lightweight particle that "orbits" outside of the
atomic nucleus. Chemical bonding is essentially the interaction of
electrons from one atom with the electrons of another atom. The
magnitude of the charge on an electron is equal to the charge on a
proton. Electrons surround the atom in pathways called orbitals. The
inner orbitals surrounding the atom are spherical but the outer orbitals
are much more complicated.
• Chemical Bonding
Chemically bonding occurs when two particles can exchange or combine
their outer electrons in such a way that is energetically favorable. An
energetically favorable state can be seen as analogous to the way a
dropped rock has a natural tendency to fall to the floor. When two atoms
are close to each other and their electrons are of the correct type, it is
more energetically favorable for them to come together and share
electrons (become "bonded") than it is for them to exist as individual,
separate atoms. When the bond occurs, the atoms become a compound.
Chemistry in a Nutshell (continued)
• Chemical Reactions
Chemical reaction re-arrange chemical bonds and atoms to form new
substances. The elements are the same, the molecules are different.
The change is associated with breaking or forming bonds that absorb or
release energy in the form of heat, light and/or sound. In a chemical
reaction the identity of the atoms and the mass of the atoms remains
the same.
• Conservation of Matter
In an ordinatry chemical reaction, matter is neither created nor destroyed.
Web Links
• http://www.chem4kids.com/files/matter_intro.html
• http://www.chem4kids.com/
http://utahscience.oremjr.alpine.k12.ut.us/pestl_courses/
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