Chemistry Final 1 Answers
There should be three categories of variables in every
experiment: dependent, independent, and controlled.
Dependent -- is what will be measured; it's what the
investigator thinks will be affected during the experiment.
For example, the investigator may want to study coffee bean
growth. Possible dependent variables include: number of beans,
weight of the plant, leaf surface area, time to maturation, height
of stem.
Independent -- is what is varied during the experiment; it is
what the investigator thinks will affect the dependent variable.
In our coffee bean example, possible independent variables
include: amount of fertilizer, type of fertilizer, temperature,
amount of H2O, day length, all of these may affect the number
of beans, weight of the plant, leaf area, etc.
Key : Since you need to know which factor is affecting the
dependent variable(s), there may be only one independent
variable. The investigator must choose the one that he/she thinks
is most important. But the scientist can measure as many
dependent variables as he/she thinks are important indicators of
coffee bean growth.
Controlled -- the variables held constant. Since the investigator
wants to study the effect of one particular independent variable,
the possibility that other factors are affecting the outcome must
be eliminated.
Chemistry Final 1 Answers
For example, the above scientist must ascertain that no
differences in the type of fertilizer used exists, or amount of
H2O, variations of temperature, or day length exist.
Graphing variables
In both math and science, dependent and independent variables
can be plotted on the x and y axes of a graph. There is typically
a clear and obvious relationship between x and y shown on the
graph.
An independent variable is the variable you have control over,
what you can choose and manipulate. A dependent variable is
the variable being tested in a scientific experiment.
The dependent variable is 'dependent' on the independent
variable. As the experimenter changes the independent variable,
the change in the dependent variable is observed and recorded.
The independent variable should be plotted on the x-axis. The
dependent variable should be plotted on the y-axis.
Generating a Hypothesis
We refer to it as a process of making “educated guesses”
because there are two elements involved. One, we need some
background knowledge or prior experiences (the “educated”) to
make a prediction. Second, we need to use that knowledge in an
active way (the “guess”).
Chemistry Final 1 Answers
Positive and Negative correlation
Direct or positive correlation- This is where the two variables
do the SAME THING. That is, if one increases so does the other
and vice versa.
Inverse or negative correlation - This is where the two
variables do the OPPOSITE. If one variable increases, the other
variable decreases.
An argument is a discussion or disagreement among scientists
regarding a specific topic that will later be tested for evidence
that can support the initial claim. A claim is the actual scientific
argument.
Evidence is any scientific facts that may be used to support the
argument or claim including data.
Reasoning is explaining your position as to why the provided
evidence can be used to support your claim. This must include
the scientific explanation supported by data and wrapped up
with a conclusion to support your claim.
Define the following branches of Chemistry
Organic Chemistry: The branch of chemistry, originally
limited to substances found only in living organisms, dealing
with the compounds of carbon. (the chemistry of carbon
compounds)
Chemistry Final 1 Answers
Biochemistry: The branch of science concerned with the
chemical and physicochemical processes that occur within living
organisms.
Physical Chemistry: The branch of chemistry concerned with
the application of the techniques and theories of physics to the
study of chemical systems.
Nuclear chemistry: Nuclear chemistry is the subfield
of chemistry dealing with radioactivity, nuclear processes, such
as nuclear transmutation, and nuclear properties.
Chemical vs. Physical Change
The difference between a physical Change and
a chemical change is composition. In a chemical reaction, there
is a change in the composition of the substances in question; in
a physical change there is a difference in the appearance, smell,
or simple display of a sample of matter without a change in
composition.
Chemistry Final 1 Answers
Examples of a chemical change
The Statue of Liberty gets its blue-green color from patina
formed on its copper surface mainly through oxidation along
with several other chemical reactions.
Examples of Physical change
Chemistry Final 1 Answers
Endothermic Vs. Exothermic Reactions.
An exothermic process releases heat energy (Bond Formation).
Freezing water
An endothermic process absorbs heat energy (Bond Breaking).
Melting Ice
Chemistry Final 1 Answers
In the picture below each point depicts a specific change
during before or after a phase change. Describe what is
happening at each point.
A-B The intermolecular forces in the solid will begin to
weaken due to an increase in vibration of the molecules as
the temperature increases.
B-C molecules will begin to break apart as they move from
the solid phase to a liquid phase.
C- D As the temperature increases the intermolecular forces
of the now liquid is weakening and the liquid is in transition
to begin evaporation.
D-E Evaporation begins and continues as the temperature
increases until the whole liquid turns into Gas.
Chemistry Final 1 Answers
E-F All the molecules that were in the system turn into the
gas phase.
Intermolecular forces
The molecules in a solid and liquid must attract each other, with
forces that are much weaker than the forces which attract atoms
to each other within a molecule.
These INTERMOLECULAR attractive forces must be stronger
in solids, weaker in liquids, and mostly nonexistent in gases.
Chemistry Final 1 Answers
Solids have a better conduction than liquids due to the close
proximity of the molecules that send the heat or energy much
faster than liquids which has molecules that are further apart and
takes longer for the transfer of energy to happen, and in turns
much less conduction in gases.
During Melting the intermolecular forces of the solid become
weaker as the molecules vibrate faster due to the increase in
temperature and therefore moving the molecules further and
further apart until the whole solid melts and becomes liquid.
The company may choose carbon because it has the closest
chemical and physical properties as Silicone and the same
Chemistry Final 1 Answers
electronegativity. It cannot be Germanium because carbon is the
only other non-metal within that group therefore matching its
chemical and physical properties.
Xenon is a non-metal because the question mentions that it is a
gas, and the fact that it is non-reactive insures that it is in group
8 which is a noble gas.
Chlorine Bromine and Iodine are all in the same group therefore
they will have same oxidation and similar chemical and physical
properties.
Germanium and silicone could be the element in question
because it has similar chemical properties (same Group), but
silicone has a lower atomic mass.
Nitrogen and oxygen -----covalent ----N2O3------Dinitrogen
Trioxide
Calcium and Fluorine-----Ionic -------CaF2------Calcium
Fluoride
Carbon and Fluorine-----Covalent------CF4----Carbon Tetra
fluoride
Lithium and Sulfur------Ionic -----Li2S------Lithium Sulfide
NaBr------Sodium Bromide
SF6--------Sulfur Hexa Fluoride
P4S5-------tetra phosphorus Penta sulfide
Ca3N2---- Calcium Nitride
MgCl2-----Magnesium Chloride
Chemistry Final 1 Answers
Write the formulas for the following compounds:
Aluminum chloride ----- AlCl3
Magnesium bromide----MgBr2
Nitrogen tribromide ----NBr3
Iodine pentafluoride----IF5
Apply the conservation of mass to balance the following
chemical equations:
____ N2 + __3__ H2 -----> __2__ NH3
____ MgF2 + ____ Li2CO3 ------> ____ MgCO3 + __2__ LiF
__2__ Al + __6__ HCl -------> __3__ H2 + __2__ AlCl3
____ P4 + __3__ O2 -------> __2__ P2O3
Create a model/diagram that represents a and d above and
include a key with each of your models
____ N2 + __3__ H2 -----> __2__ NH3
+
----->
____ P4 + __3__ O2 -------> __2__ P2O3
+
------->
a. Sodium + magnesium chloride → Magnesium + Sodium
Chloride
Chemistry Final 1 Answers
b. Calcium + sodium chloride → Sodium +Calcium Chloride
c. Barium + lithium fluoride→ Lithium + Barium Chloride
d. Rubidium + aluminum oxide → Aluminum + Rubidium
Oxide
Describe the atomic model with regards to empty space and
the nucleus
The Atom has a nucleus containing the protons and Neutrons
that is surrounded by an electron cloud. The number of
Electrons can change when bonding. The number of neutrons
can change when the atom has an Isotope, but the number of
protons always remains the same.
Identify the location, mass, and charge of each of the three
subatomic particles within an atom.
Provide the number of protons and electrons for the
following:
Chemistry Final 1 Answers
Sodium atom
Sodium ion with a charge of +1
Calcium ion with a charge of +2
oxygen atom
Nitrogen ion with a charge of -3
Chemistry Final 1 Answers
Chlorine atom
Chlorine ion with a charge of -1