Transcript Chemistry Q2 Benchmark Review

Chemistry Q4
Amazing Benchmark
Review
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Example 2:
Standard 8a: Know the rate of reaction is the
decrease in concentration of reactants or the
increase in concentration of products with time.
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How would you identify
the reaction rate?

The change of reactants or products over
time
–

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Decrease of reactants or Increase of products
over time.
C4H9Cl + H2O  C4H9OH + HCl
Conditions That Affect Reaction
Rates
1. Concentration – higher concentration of
reactants lead to more collision
2. Temperature – speed of molecules increase with
increase temperature, so the average collision is
more energetic
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Example 3:
Standard 8b: Know how reaction rates depend on
such factors as concentration, temperature, and
pressure.
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Define Collision
Theory

Collision Theory: atoms, ions, and molecules
must collide with each other in order

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to react
Anything that makes atoms collide more
faster increases the reaction rate.
Le Chatelier’s Principle
25kj + N2O4 (g)
2NO2 (g)
(Ea)
1.
2.
3.
4.
5.
6.
7.
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8.
CHANGE:
Addition of N2O4
Addition of NO2
Removal of N2O4
Removal of NO2
Decrease of container volume
Increase of container volume
Increase of temperature
Decrease of temperature
SHIFT PREDICTION :
Right
Left
Left
Right
Left
Right
Right
Left
Example 4:
Standard 8c: Know the role a catalyst plays in
increasing the reaction rate.
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Conditions That Affect Reaction
Rates

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Catalyst (enzyme): a substance that speeds up a chemical
reaction without being consumed (meaning it recycles)
Example 1:
Standard 9a: Know how to use Le Chatelier’s
Principle to predict the effect of changes in
concentration, temperature, and pressure.
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Le Chatelier’s Principle

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Le Chatelier’s Principle – when a change is imposed on a system at
equilibrium, the position of the equilibrium shifts in a direction that
tends to reduce the effect of that change
–
This principle allows us to predict the effects of a system at equilibrium by
changes in (1) concentration, (2) pressure, or (3) temperature.
–
The goal is for the equilibrium to lie far to the right toward products.
Example 5:
Standard 9b: know equilibrium is established
when forward and reverse reaction rates are
equal.
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Chemical Equilibrium: A Dynamic
Condition


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A chemical reaction has reached chemical equilibrium
when the concentrations reach levels at which the rate of
the forward reaction equals the rate of the reverse
reaction.
Equilibrium (K)
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Example 6:
Standard 11a: know protons and neutrons in
the nucleus are held together by nuclear
forces that overcome the electromagnetic
repulsion between the protons.
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The Strong Nuclear Force – 11a
What is the strong nuclear
force and what does it do in an
atom?


The nucleus is composed of two types of nucleons,
protons and neutrons.
The nucleus is held together by the strong nuclear
force.
–

Even though two protons should repel each other,
this SNF is able to overcome this repulsion, but only
when they’re really close together.
–
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This is an attraction between the nucleons.
The SNF is actually stronger than the
electromagnetic force at close distance!
Example 7
Standard 11b: know the energy
release per gram of material is
much larger in nuclear fusion or
fission reactions than in
chemical reactions. The change
in mass (calculated by E =
mc^2) is small but significant in
nuclear reactions.
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Example 7: Nuclear Fission
The decay of a single U-235 atom releases approximately 200 MeV (million
electron volts). That may not seem like much, but there are lots of uranium
atoms in a pound of uranium. So many, in fact, that a pound of highly enriched
uranium as used to power a nuclear submarine is equal to about a million
gallons of gasoline.
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Energy from Nuclear Reactions
E=mc2
Energy
produced
from the
Nuclear
Reaction
Difference
in mass
between
products
and
reactants
Very Large
Constant
(Speed of Light)2
Because the constant is so large, tiny
amounts of mass produce tons of energy
Where does the energy come from ?
In chemical reactions the energy comes from the bonds,
In nuclear reactions the energy comes from the conversion of
mass to energy
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Example 8:
Standard 11c: know some naturally occurring
isotopes of elements are radioactive, as are
isotopes formed in nuclear reactions.
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Example 8:
Naturally occurring Isotopes:
Isotopes from nuclear reaction:
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Example 9
Standard 11d: know the three most common
forms of radioactive decay (alpah, beta, and
gamma) and know how the nucleus changes in
each type of decay.
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Types of Radioactive Decay: Number 1
Alpha-particle production

Alpha (a) particle – produces helium (4/2He)
nucleus
–
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For example:
• Net effect is loss of 4 in mass number and loss of 2 p+
in atomic number.
Types of Radioactive Decay: Number 2
Beta-particle production
• Beta (B) particle – releases electron (0/-1 e)
For example:
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• Net effect is to change a neutron to a proton. Thus;
atomic number increase by 1.
Types of Radioactive Decay: Number 3
Gamma ray release
• Gamma (Y) ray – release of 2 rays of high energy
photons and 1 alpha particle (4/2 He)
– For example: energy photons have no effect on
element
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Example 10
Standard 11e: know alpha, beta, and gamma
radiation produce different amounts and kinds of
damage in matter and have different
penetrations.
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Example 10:
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
Alpha: gets stopped by a few centimeters of air or a thin sheet of
paper. You may think that this means alpha radiation is quite weak
but in fact the opposite is the case. Very Dangerous for atoms/cells!
20X more damaging than other rays—called ionization.

Beta: goes through a few meters of air and is stopped by a thin
piece of lead. Less dangerous for atoms/cells. Example: X-rays.

Gamma: are like a wind blowing over our lawn. Gamma rays can
pass through a thin sheet of lead with very little effect. You need
about 10 cm of lead to stop most gamma rays completely.
Example 11
Standard 10a: know large molecules (polymers),
such as proteins, nucleic acids, and starch, are
formed by repetitive combinations of simple
subunits.
monomer
polymers
Note: amino acid
 proteins
nucleotide
 nucleic acids
simple sugars  starch
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Polymers
• Polymers – large chainlike molecules made from many
small molecules called monomers
– Simplest polymer: polyethylene
– Polymerization is the process in which monomers are
added together to form polymers.
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Polymers

Condensation polymerization – a small
molecule (often water) is released for each
addition of a monomer to the polymer chain
– For example: Nylon
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Example 12
Standard 10b: know the bonding characteristics of
carbon that result in the formation of a large
variety of structures ranging from simple
hydrocarbons to complex polymers and
biological molecules.
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Carbon Chemistry
Carbon is an element that
1. Can bond strongly to itself (C—C)
2. Can form long chains or rings (C—C—C—C—C…)
3. Can bond to other nonmetals: H, N, O, S, and
halogens.
4. Thus, there are many types of carbon compounds
Biomolecule – molecule that functions in
maintaining and reproducing life
Organic compounds – vast majority of carbon
compounds
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Alkanes

Alkanes are saturated hydrocarbons with tetrahedral
structures with the general formula CnH2n+2 with n = 1,
2, 3, 4, 5….
CH4
methane
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C2H6
ethane
C3H8
propane
C4H10
butane
Example 13
Standard 10c: know amino acids are the building
blocks of proteins.
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Primary Structure of Proteins

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amino acids (20 types) – building blocks of all
proteins
• R groups (side chains) – may represent H, CH3 or more
complex substituents
• Amino group (NH2) and carboxyl group (COOH) are
always attached to the carbon.
Structure of Proteins
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