Station 1:
Kinetic Molecular Theory & Temperature
1) Visit each site listed below. Answer the questions listed for each site on the Google doc provided.
Kinetic Molecular Theory: Basic Concepts
http://www.chm.davidson.edu/vce/KineticMolecularTheory/BasicConcepts.html
a.
b.
c.
d.
e.
Questions:
1. Summarize the 5 basic postulates
A gas consists of a collection of small particles traveling in straight-line motion and obeying
Newton's Laws.
The molecules in a gas occupy no volume (that is, they are points).
Collisions between molecules are perfectly elastic (that is, no energy is gained or lost during
the collision).
There are no attractive or repulsive forces between the molecules.
The average kinetic energy of a molecule is 3kT/2. (T is the absolute temperature and k is the
Boltzmann constant.)
2. Read and observe both simulations, what are the simulations showing you about average kinetic energy of
particles?
A: In the first simulation, the one particle speed never changes as it bounces inside the container.
In the second, the particle speed changes when it collides with a particle of a different speed. In
either case, when averaged over a period of time, the average kinetic energy of the molecule is still
3kT/2.
Kinetic Molecular Theory: Temperature http://students.ed.uiuc.edu/mrayon/temperature.html
Questions:
3. How is temperature defined?
A: The temperature of a substance is a measure of the average kinetic energy of the particles that
make up the substance.
4. What is a misconception of students with respect to temperature and the effect on gasses? What really
happens?
A: If you increase the temperature of a gas, the size of the gas particles increase in size. An
increase in temperature only causes the gas particles to move faster and expand, not increase in
size!
Kinetic Molecular Theory: Diffusion http://www.chm.davidson.edu/vce/KineticMolecularTheory/Diffusion.html
Questions:
5. Describe the motion of the red particle in the first simulation. Be detailed, please.
A: The movement of the red particle is such where it only moves short distances (in a straight line)
until it hits another particle; at that point, the particle then changes direction. There is no
predetermined path that the red particle travels. Each time the simulation is set, there is a different
path that the red particle travels.
6. In the second simulation, why doesn’t the red particle follow a straight line path?
A: The particle doesn’t follow a straight path as it is constantly being bombarded by the other
particles.
2) Complete the Demonstrations described below.
Kinetic Theory Made Visible
Materials:
5 glass marbles
clear plastic container with lid
5mL 12M HCl
5mL of conc. NH3(aq)
2 wide mouth gas collecting bottle with stoppers
Procedure:
1. Have students observe the collisions of the marbles with each other and with the walls of the container.
2. Simulate the effect of increase temperature by moving the box rapidly. Have students not changes in the motion of the
marbles.
3. In a fume hood, place a small amount of 12M HCl in one of the wide mouth collecting bottle and stopper it. Place a
similar amount of concentrated NH3(aq) in the second collecting bottle and stopper it.
4. Open both bottles in the fume hood. Have students observe the formation of NH4Cl "smoke". Carefully do this under
a hood because these vapors are harmful.
A: During these demonstrations you should have seen that with increase temp (motion of hand moving
the particles, the particles moved faster. In addition, you should have seen the “smoke” forming
closer to the HCl bottle because HCl is a heavier particle and moves slower than the NH3 particle.
3)
After the unit is complete the quiz can be taken at this site (16 questions)
http://www.sciencegeek.net/Chemistry/taters/Unit5KMT.htm
1.
If all of the following flasks are the same size, at the same temperature, and contain the same number of molecules, in which
flask will the pressure be highest?
A.
?
Flask 2
B.
?
Flask 4
C.
?
Flask 3
D.
?
Flask 1
E.
2.
:-) All have the same pressure
Which of the following gases would have the fastest rate of diffusion, assuming all of the gases are at the same temperature?
A.
B.
?
Ar
:-) He
3.
C.
?
Ne
D.
?
Kr
Gas pressure is caused by:
A.
?
gas molecules hitting other gas molecules
B.
?
barometers
C. :-) gas molecules colliding with surfaces
D.
?
gas molecules condensing to a liquid
4.
If all of the following flasks are the same size, at the
same temperature, and contain the same number of
molecules, in which flask will the molecules be
moving slowest?
A.
5.
:-) Flask 4
B.
?
Flask 2
C.
?
Flask 1
D.
?
Flask 3
Four different flasks contain gas samples at 298 K. In which of the following samples will the gas molecules be moving the
slowest?
A.
B.
?
H2
:-) CO2
C.
?
N2
D.
?
O2
6.
Each of these flasks contains the same number of gas molecules. In which would the pressure be lowest?
A.
?
Flask 4
B.
?
Flask 3
C. :-) Flask 1
D.
7.
?
Flask 2
Which of the following gases would have the slowest rate of diffusion, assuming all of the gases are at the same temperature?
A.
:-) Kr
B.
?
He
C.
?
Ar
D.
?
Ne
8.
Each of these flasks is the same size and at the same temperature. In which flask will diffusion occur most slowly?
A.
:-)
Flask 4
B.
?
Flask 2
C.
?
Flask 1
D.
?
Flask 3
9.
Each of these flasks is the same size and at the same temperature. Which one contains the fewest molecules?
A.
?
Flask 3
B.
?
Flask 2
C.
?
Flask 4
D. :-) Flask 1
10.
Each of these flasks contains the same number of gas molecules. In which would the pressure be highest?
A.
:-) Flask 4
B.
?
Flask 1
C.
?
Flask 2
D.
?
Flask 3
11. Four different flasks contain gas samples at 298 K. In which of the following samples will the gas molecules be moving the
fastest?
A.
?
O2
B.
?
N2
C. :-) H2
D.
?
CO2
12.
Each of these flasks contains the same number of molecules. In which container is the pressure highest?
A.
?
Flask 2
B.
?
Flask 3
C. :-) Flask 1
D.
?
Flask 4
13.
Each of these flasks is the same size and at the same temperature. Which one contains the most molecules?
A.
B.
?
Flask 2
:-) Flask 4
C.
?
Flask 3
D.
?
Flask 1
14.
Each of these flasks contains the same number of
molecules. In which container is the pressure
lowest?
A.
?
Flask 1
B.
?
Flask 2
C.
?
Flask 3
D. :-) Flask 4
15.
If all of the following flasks are the same size, at the same temperature, and contain the same number of molecules, in which
flask will the molecules be moving fastest?
A.
B.
?
Flask 4
:-) Flask 1
C.
?
Flask 2
D.
?
Flask 3
16. Which of the following changes to a system WILL NOT result in an increase in pressure?
A.
?
Adding more gas molecules
B.
?
Decreasing the volume of the container
C.
?
Raising the temperature
D. :-) Increasing the volume of the container
Station 2:
Phase Changes
Visit the following sites. Using each site, answer the questions that I pose on the Google doc.
Phase Changes Animation: http://nuweb.neu.edu/bmaheswaran/phyu121/data/ch04/anim/anim0405.htm
1. Temperature is related to the average kinetic energy of the particles of the material. During a phase
change, the temperature of the material is constant. (For example, ice melts at zero Celsius.) What
does that imply about the average kinetic energy of the particles in each of the two phases?
A: The average kinetic energy of a solid & liquid or a liquid & solid are equal to each other.
2. Usually, adding heat to a substance causes the particles to increase in kinetic energy and the
temperature rises. Since that does not happen during a phase change, where does the heat energy
go?
A: Heat energy is used to change phases. (Energy is needed to break the cohesion of particles of a
solid so they become a liquid).
3. Why is the energy needed to convert a liquid to a gas usually very much larger than the amount of
energy needed to convert a solid to a liquid?
A: The intermolecular bonds of a liquid are harder to break so more energy is needed to make a
substance a gas.
4. A radiator or pressure cooker allows a liquid to achieve a higher temperature than normal boiling by
sealing off the system from the surroundings. Based on the definition of boiling and this animation, how
is that possible?
A: If you change the pressure above the surface of a liquid, the boiling point can be changed as well.
In addition, the temperature of the gas (vapor) can get much higher than the liquid. By sealing in the
gases, you can continue to heat those gases to a higher temperature to cook the food.
Experiment – Phase Changes http://www.chm.davidson.edu/ronutt/che115/Phase/Phase.htm
(This is another site that will help with some of these concept questions http://zonalandeducation.com/mstm/physics/mechanics/energy/heatAndTemperature/changesOfPhase/change
OfState.html )
5. Select "weak" for the intermolecular forces and temperature T1. Allow the system to achieve
equilibrium. Briefly characterize the vapor and liquid phases.
A: Particles quickly and easily became vapor particles. There were many particles in the vapor phase.
The vapor pressure of this substance was 0.871
6. Select "strong" for the intermolecular forces and temperature T1. Allow the system to reach equilibrium.
Briefly describe the process of phase change.
A: Particles were slow to become a vapor. There were fewer particles in the vapor phase. The vapor
pressure of this substance was 0.290
7. Select "strong" for the intermolecular forces and allow the system to achieve equilibrium at temperature
T1. Repeat the experiment with the temperature set at T2 and then T3. How does the average number
of molecules in the vapor phase change with a change in the temperature and why?
A: The average number of particles increases with an increase in temperature. (7,190 to 11,186 to
23,173). This happens because with more energy, particles are able to break free from the
intermolecular forces holding the liquid particles together, thus increasing the vapor pressure.
8. Select temperature of T2 and allow the system to achieve equilibrium at each of the intermolecular
forces of attraction (weak and strong). How does the vapor pressure change with a change in the
magnitude of the intermolecular forces of attraction in the liquid phase and why?
A: The weaker the intermolecular force, the more particles in vapor form and the higher the vapor
pressure. This is because less energy is needed to overcome the forces holding particles together as
a liquid so there more particles getting into the gas phase.
9. Define vapor pressure.
A: Vapor pressure is the pressure exerted by a vapor in equilibrium with its condensed phases (solid
or liquid) at a given temperature in a closed system. The equilibrium vapor pressure is an indication of
a liquid's evaporation rate. It relates to the tendency of particles to escape from the liquid (or a solid).
Phase Changes – Heating Curve http://www.chm.davidson.edu/vce/PhaseChanges/HeatingCurve.html
10. Why are there regions where the temperature does not change with time, despite the fact that heat is
being added to the system?
A: The regions where temp does not increase are where the phase changes are occurring.
11. In most cases, the transfer of heat to an object increases its temperature. In the regions where the
temperature does not change as heat is flowing into the substance, what change is the heat producing?
A: A change in phase is occurring.
12. What is the melting point of the substance?
A: MP = 55°C
13. What is the boiling point of the substance?
A: BP = 147°C
14. How does the heating curve for a 400 W heating rate compare with that obtained using a 200 W
heating rate? (Be quantitative in your answer.) Do the melting point and boiling point depend upon the
heating rate?
A: MP and BP are not changed. The rate (speed) at which they reach the MP and BP do change. At
200W it took 8 seconds to get to a liquid and 27 seconds to get to a gas; at 400W it took half that time
(4 seconds to get to a liquid and 13 seconds to get to a gas).
Station 3:
Boyle’s Law
Conduct the Lab using the handout provided at the station. You will be using a device called a LAB QUEST. It
allows you to program some information and some it will read for you. When completed, it will allow you to see
a graph, a data table or even do other evaluations of the data. Just follow the directions for the lab on the
provided handout. When completed, answer the questions for the lab using the Google document provided on
the wiki.
There are plenty of copies of the lab that you may take one to keep. This will allow you to work on the
questions after class and still be able to submit your answers electronically.
Here are some websites that can help you with your questions with the lab:
1. Boyle’s Law Concepts http://www.chm.davidson.edu/vce/GasLaws/BoylesLaw.html
2. Animated from NASA http://www.grc.nasa.gov/WWW/K-12/airplane/aboyle.html
3. Online experiment
http://group.chem.iastate.edu/Greenbowe/sections/projectfolder/flashfiles/gaslaw/boyles_law_graph.ht
ml
4. ThinkQuest site http://library.thinkquest.org/12596/boyles.html
Misconception warning: There is a difference between an elastic container (ex: balloon) and a non-elastic
container (ex: scuba tank). Boyle’s law is best described using non-elastic containers as an example. The law
says as volume decreases, as when a piston is pushed down, the contained gas has more collisions with the
wall of the container so pressure increases. Or if one transfers a given amount of a gas from a small scuba
tank to a larger scuba tank, the pressure is less in the large scuba tank due to an increase in volume. This
misconception can arise when one is dealing with a stretchy container, such as a balloon. As one adds gas to
a balloon, the balloon expands (volume increases) due to an increase in the number of collisions (pressure)
between the contained gas and the inner walls of the balloon. This could result in the student drawing the
conclusion that pressure and volume share a direct relationship.
Answers to the lab questions:
1.
2.
3.
4.
5.
6.
7.
8.
9.
When volume is doubled from 5 to 10 ml, the pressure is cut in half
When the volume is halved from 20 to 10 ml, the pressure is doubled
When the volume is tripled from 5 to 15 ml, the pressure is cut by 1/3.
The graph shows an inverse relationship (parabola shape). As the Volume increases, the
Pressure decreases.
If the pressure for 20 ml was 0.5 atm, & if the volume doubled to 40 ml, the pressure should be
0.25 atm.
If the pressure for 5 ml was 1.5 atm, & if the volume was cut in half to 2.5 ml, the pressure
should be 3.0 atm
Factors kept constant were the TEMPERATURE of the gas, the NUMBER OF GAS PARTICLES
and the KIND OF GAS USED.
PV=k ; if the pressure is multiplied by the volume of a gas, it should equal a constant.
P1V1=P2V2
Station 4:
Gay Lussac’s Law
Conduct the Lab using the handout provided at the station. You will be using a device called a LAB QUEST. It
allows you to program some information and some it will read for you. When completed, it will allow you to see
a graph, a data table or even do other evaluations of the data. Just follow the directions for the lab on the
provided handout. When completed, answer the questions for the lab using the Google document provided on
the wiki.
There are plenty of copies of the lab that you may take one to keep. This will allow you to work on the
questions after class and still be able to submit your answers electronically.
Here are some websites about Gay Lussac’s Law to help you answer the questions.
1. The Law explained http://www.chemteam.info/GasLaw/Gas-Gay-Lussac.html
2. Animating the law http://www.grc.nasa.gov/WWW/k-12/airplane/aglussac.html
3. A really good ppt http://jcozart.myweb.uga.edu/gaylussacslaw.ppt
4. A site called a Better Chem Text http://abetterchemtext.com/gases/G_lussac.htm
Answers to the Lab Questions:
1. Experimental factors that need to stay constant are the VOLUME of the gas and NUMBER OF
GAS PARTICLES/KIND OF GAS.
2. As the Temperature increases, the pressure also increases.
3. As the Temperature increases, the particles move faster which means there will be more
collisions with the container and the number of collisions indicate the pressure of the gas.
(Greater Pressure)
4. P / T = k
5. Temperature needs to be in Kelvin because that scale is the Absolute Temperature. This is the
only scale in which there are NO NEGATIVE TEMPERATURES. Since there are no negative
volumes or negative pressures, when we work with gases we cannot have negative
temperatures.
6. This graph showed a DIRECT RELATIONSHIP. As the temp increased, so did the pressure.
These showed constants that were very close (all near 0.33)
7. If the temperature doubles, the pressure should also double.
Station 5:
Charles’s Law
1) Visit each site listed below. Answer the questions listed for each site on the Google doc
provided.
**Charles’ Law Concepts: http://www.chm.davidson.edu/vce/GasLaws/CharlesLaw.html
Questions:
1. After completing the virtual lab you will have a graph made. At what Celsius temperature does the
volume equal 0 mL?
A: Should be around -273 °C
2. Was the graph a direct or inverse relationship?
A: Direct – as temp increased, so did the volume
**ThinkQuest Site: http://library.thinkquest.org/12596/charles.html
Questions:
3. Describe the relationship between volume and temperature using kinetic energy and molecular motion.
A: As the temperature increases, the kinetic energy of the particles is greater therefore the particles
are moving more and colliding with the container walls more. If the container walls are flexible, the
container’s volume will increase.
4. Why must the temperature scale be in Kelvin instead of any other? How do you convert a Celsius
temperature to Kelvin?
A: The Kelvin scale is the absolute temperature scale – it starts at a 0 value (all molecule motion
ceases) and increases from there. °C and °F both have negative values. Conversion is taking the
°C value and adding 273 to get the Kelvin temperature.
**Gas Volumes and Heat: http://www.aquaholic.com/gasses/charles.htm
Questions:
5. What is the concern about SCUBA gear with respect to Charles’ Law as described in this site?
A: For example a full scuba tank, if left in the sun, will heat up. This causes the molecules in the air
in the tank to move faster. The tank is a rigid container that will not expand. This increase in
motion then raises the pressure inside the tank. In fact, a full scuba tank will gain about 5-6 psi for
every degree of temperature increase. This is one reason that full tanks should not be left in a hot
trunk of a car. A tank filled to 3000 psi could easily reach 3500 psi if the temperature of it increased
substantially.
**Animation of Charles’ Law http://preparatorychemistry.com/Bishop_Charles_frames.htm
Questions:
6. What are the four (4) properties of a gas?
A: Temperature, Pressure, Volume and Number of particles (number of moles)
7. What happens to the velocity of gas particles as the temperature increases? How does this affect the
volume?
A: As the temperature increases, the velocity of a gas also increases. Since particles move faster,
the particles move to occupy more space. If the container is flexible, the volume increases.
8. What has to remain constant in Charles’ Law for the relationship of temperature and volume to be
seen?
A: The Pressure of the gas and the Number of gas particles need to stay constant.
2) Demonstrations with Charles’ Law. Complete each and answer the questions using
Google docs
**Charles’ Law: Balloon in a freezer
a) Note the size of an inflated balloon.
b) Place an inflated balloon inside a freezer for 10 minutes.
c) Note the size after 10 minutes.
** Charles' Law: Imploding Can
a) Place a few drops of water inside the aluminum can and then heat it until the water begins to boil.
b) Using tongs, quickly invert the can so that the opening is in a beaker of cold water.
**Charles’ Law and Ivory Soap
a) Place a section of a cut up bar of soap onto one glass plate.
b) Set the microwave for 2 minutes. (note, stop it before the soap spills over the plate).
(Read more here http://theexplorationstation.wordpress.com/2009/11/24/exploring-density-and-charles-lawusing-ivory-soap/ )
Questions:
9. Using Charles’ Law, what is the reason for the balloon size changing?
A: The particles were slowing down and needed to occupy less space while in the freezer so the
balloon decreased in size.
10. Using Charles’ Law, what was the reason why the can size changed?
A: The heat added made the particles move faster and since the can is more rigid than a balloon
and was open to the atmosphere, the particles left the can (now fewer particles of gas in there than
before. When the can is transferred to the cold water, the water seals the opening so gas cannot
leave or enter. The water also cools the remaining particles – they slow down – less collisions –
less pressure inside the can and the outer pressure of the air is greater than in the can the air
crushes the can.
11. Using Charles’ Law, what is the reason why the soap changed?
A: The soap has air spaces in it. When the air is heated, it moves faster and wants to occupy more
space. The soap is flexible and the soap increases in size due to the particles pushing on the
flexible soap particles.
Station 6:
Pressure (Converting between units), Dalton’s Law of Partial Pressures & Avogadro’s Law
**Converting between atmospheres, kilopascals and mmHg.
http://www.chemteam.info/GasLaw/PressureConversions.html
Questions:
Convert 1.69 atm to mmHg
A: 1.69 atm × 760 mmHg = 1284.4 mmHg
1 atm
Convert 0.3587 atm to kPa
A: 0.3587 atm × 101.3 kPa = 3.63 kPa
1 atm
**Dalton’s Law: http://chemistry.tutorvista.com/physical-chemistry/daltons-law-of-partial-pressure.html
Questions:
What is the formula for Dalton’s Law of Partial Pressures?
A: Ptotal = P1 + P2 + P3 ….
What is the most important application of Dalton’s Law?
A: The most important application of the Dalton’s Law of partial pressure is finding out the volume of
the gas when it is collected over water.
**Partial Pressures – Scuba http://www.aquaholic.com/gasses/dalton.htm
Questions:
How is this law important to us when we consider SCUBA diving?
A:
Determine the partial pressure of oxygen at a depth of 25 feet in fresh water.
A: Oxygen makes up 21% of our atmosphere, Freshwater exerts 0.432 psi per foot in depth of water,
the atmospheric pressure on us at sea level is 14.7 psi. These values are used to answer this question.
0.432 psi/ft × 25 ft = 10.8 psi
10.8 psi + 14.7 psi (air pressure) = 25.5 psi
25.5 psi × 0.21 (% of O2 in the air) = 5.355 psi is the partial pressure of O2
**PhET interactive site http://phet.colorado.edu/en/simulation/gas-properties
1. Press the Green “RUN NOW” tab.
2. On the top right select VOLUME to stay constant.
3. Add Gas to the chamber by using the arrows next to HEAVY SPECIES so that there are 25 particles of
gas. Record the pressure.
4. Add more particles of the HEAVY SPECIES so there are 50 particles. Record the pressure.
5. Do this again so there are 100 particles of the HEAVY SPECIES. Record the pressure.
A: 25 particles = 0.15 atm; 50 particles = 0.26 atm; 100 particles = 0.52 atm
6. Reset options (bottom tab on the right)
7. Add Gas to the chamber by using arrow next to the LIGHT SPECIES so that there are 25 particles of
gas. Record the pressure.
8. Add more particles of the LIGHT SPECIES so there are 50 particles. Record the pressure.
9. Do this one more time so there are 100 particles of the LIGHT SPECIES. Record the pressure.
A: 25 particles – 0.10atm; 50 particles = 0.26 atm; 100 particles = 0.50 atm
10. Reset options.
11. According to Dalton’s Law of partial pressures, what would be the total pressure if you were to add the
25 HEAVY SPECIES particles and the 25 LIGHT SPECIES particles into one container? Check this
out by doing just that.
12. What would be the pressure of 50 particles of the HEAVY SPECIES added to 50 particles of the LIGHT
SPECIES? Check it out using the simulation.
13. Repeat with 100 particles of each.
A: 25 light + 25 Heavy = 0.25 atm; 50 light + 50 heavy = 0.51 atm; 100 light + 100 heavy = 1.03 atm
14. Does pressure depend on the mass of the particle?
A: No, mass of the particle does not affect pressure
15. The pressure of a 1-L nitrogen gas sample at 25 ⁰C is 0.30 atm. The pressure of a 1-L oxygen gas
sample at the same temperature is 0.25 atm. The oxygen gas sample is added to the nitrogen
container. Argon gas is added to the mixture until the total pressure of the 1-L container reaches 1.00
atm, and the temperature is still at 25 ⁰C. According to Dalton’s Law of Partial Pressures, the
contribution of each gas to the total pressure of the gas mixture is:
Nitrogen _____________
Oxygen _____________
Argon _____________
A: N2 = 0.3 atm
O2 = 0.25 at,
Ar = 0.45 atm
**Avogadro’s Law – Concepts http://www.chm.davidson.edu/vce/GasLaws/AvogadrosLaw.html
Avogadro’s Law simplified is P = nV (where P=pressure, n=number of moles & V=volume)
Scroll to the bottom of this site where the simulation is located. Select He gas. Press the TARE button the
scale (found under the round flask). Press and hold the “Add Gas” button until the pressure reading on the far
left is at 700 mmHg. Read and record the mass. Press and hold “Remove Gas” until the scale is back to zero.
Repeat this process with the other gases in the table. Use the periodic table to find the molar masses of each
gas and then calculate the value for “n”
Questions:
What does STP stand for (defined as well as values)?
A: STP = Standard Temperature and Pressure; Standard Temp = 0°C or 273 K; Standard Pressure =
760mmHg or 101.3 kPa or 1 atm
What do you notice about the values for “n” in the data table?
A: All the values for n are the same (0.012)
What does Avogadro’s Law state?
Avogadro studied how the amount of gas affects the volume of the gas. The law states that equal
volumes of ideal or perfect gases, at the same temperature and pressure, contain the same number of
particles, or molecules.
Complete the table below:
Pressure
Gas Type
Mass
700 mmHg
700 mmHg
700 mmHg
700 mmHg
0.048 grams
0.339 grams
0.244 grams
0.858 grams
He
N2
Ne
Cl2
Molar Mass of
Gas Type
4.0026 g/mol
28.02 g/mol
20.18 g/mol
70.9 g/mol
Calculate n = number of
moles
0.0120
0.0121
0.0121
0.0121