Torres Evelyn Chervenak wk3
Kinetic Theory
Objectives
Describe how the kinetic-molecular theory is used to explain how gases behave at different temperatures. (Exploration 1) Analyze data that shows how gas particle mass affects that gas's behavior. (Exploration 2) Based on the mass of the object, the gas particle can move quickly in higher temperature or slower depending on the mass components. Describe the Maxwell-Boltzmann Distribution. (Explorations 1 and 2) With increasing energy some of the particles will be found to be slower
Description of Activity
The kinetic-molecular theory states that a collection of gas molecules' average kinetic energy has a specific value at any given temperature. In this activity, you will study how temperature and gas particle mass affect the frequency distribution of gas particle speeds. You will examine and analyze speed frequency distribution graphs. This distribution is called the Maxwell-Boltzmann Distribution.
Jump Start
1. What is kinetic energy? It is energy in motion 2. What is thermal energy? Movement of atoms and molecules 3. What happens to a gas's thermal energy as that gas's temperature increases? The particles decreases in speed 4. What happens to the average speeds of the particles in a gas when that gas's temperature is increased? They all have the same kinetic energy
Safety Discussion
If you conduct this experiment in a laboratory setting, be aware that gases heated in a closed container could result in the container exploding.
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Evelyn Torres Chervenak wk3
Exploration 1: The Effect of Temperature on Gas Behavior
Procedure 1. Choose any gas from the list box. 2. Set Temperature to any value. Observe the shape of the frequency distribution of speeds graph. Sketch this graph. Record the most probable particle speed (vp) and the average particle speed (vavg) in Table 1. 3. Repeat step 2 for four additional temperatures. Increase the value each time. 4. Choose another gas and repeat steps 2 and 3. Observations and Analysis
Table 1 Gas Temperature (K) Most Probable Particle Speed (m/s) 1252 1462 1650 268 313 353 Average Particle Speed (m/s) 1413 1652 1862 302 354 398
Hydrogen Gas Hydrogen Gas Hydrogen Gas Carbon Dioxide Carbon Dioxide Carbon Dioxide
190K 260K 330K 190K 260K 330K
1. What happens to the particle speed as one increases the temperature? In the Hydrogen Gas the particles moves faster when the temperature increase. Whereas in the Carbon Dioxide the lower temperatures the particles move slower. 2. How does the speed frequency distribution graph change for a given gas the as temperature is increased? As for the Hydrogen Gas the particles are more widely speed as their speed increase. In the Carbon Dioxide the probable speed changes very little as the temperature rises but the particles are dense more as the speed increase.
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Evelyn Torres Chervenak wk3 3. At a given temperature, why does the most probable particle speed (vp) differ from the average particle speed (vavg)? Because the molecules are more spread out or condensed 4. When a different gas is graphed, does the trend of the graph's shape differ as the temperature is increased? Yes.
Exploration 2: The Effect of Mass on Gas Behavior
Procedure 1. Set the temperature to 500 K. Maintain this temperature throughout this Exploration. 2. Select Hydrogen gas from the list box. Record the most probable particle speed and the average particle speed in Table 2. 3. Calculate the mass of a gas particle from step 2 in amu. Refer to the periodic table for the masses of individual atoms. Be aware that a hydrogen gas particle contains two hydrogen atoms, and an oxygen gas particle contains two oxygen atoms. Record your result in Table 2. 4. Repeat steps 2 and 3 for Oxygen, Carbon dioxide, and Xenon. Observations and Analysis
Table 2 (Temperature = 500 K) Gas Most Probable Particle Speed (m/s) 2031 511 435 252 Average Particle Speed (m/s) 2291 576 490 284 Mass of a Single Atom or Molecule (amu) 60 65 55 32
Hydrogen Gas Oxygen Carbon Dioxide Xenon
1. At a given temperature, what relationship appears to exist between a gas particle's mass and its speed? 2. How does the graph change as particle mass increases? Depending on the gas some mass is condense and moves slowly. 3. One relationship that expresses the kinetic-molecular theory and the relationship between speed 3RT and mass of molecules is vrms = , where vrms = the root mean speed of the molecules M (which is nearly identical to the average speed), T = temperature of gas (K), M = mass of an individual gas particle (amu), and R = Gas constant (8.314 J/molK = 8.314 kgm2/s2molK). Calculate the vrms for hydrogen, oxygen, carbon dioxide, and xenon at 2550 K. (Remember to convert molar mass to kg/mol).
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Conclusions
What can you conclude about gas molecule speeds in a container?
Inquiry Extension
Using what you learned from this activity, explain why a balloon expands when heated and contracts when cooled.
Hydrogen Gas at 190K
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Hydrogen Gas@ 260K
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Hygrogen Gas at 330K
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