A Web-Based Molecular Level Inquiry Laboratory Activity

Michael R. Abraham, Department of Chemistry and Biochemistry, University of Oklahoma, Norman, OK 73019, Phone: 405-325-4981, Fax: 405-325-6111, MRAbraham@OU.edu, Kirk Haines, 2136 W. Sunset, Stillwater, OK 74074, haineka@okstate.edu, and John I. Gelder, Department of Chemistry, Oklahoma State University, Stillwater, OK 74078, Phone: 405-744-7005 Fax: 405-744-6007, jgelder@okstate.edu.

Presentation delivered at

221st Meeting of the American chemical Society

San Diego, CA

April 1 - April 5, 2001

 

Molecular Laboratory Experiments (MoLE) in Chemistry

Molecular Laboratory Experiments (MoLE) in Chemistry are a collection of computer-based models of molecular laboratory experiments that can be integrated and linked with parallel hands-on laboratory experiments used in introductory chemistry.

We are developing six computer-based molecular laboratory experiments and their parallel hands-on laboratory experiments around the content areas of: ideal gases (kinetic molecular theory laboratory activity/simulation), chemical equilibrium (Summer 2001), kinetics (collision theory and mechanisms), phase equilibria, solution process and atomic structure. These topics were chosen because they especially lend themselves to modeling using interactive computer graphics and to integrating the three levels of chemical understanding (particulate, sensory, and symbolic).

The instructional materials have the following characteristics:

(a) allow students to model laboratory experiments at the molecular level;

(b) facilitate the linking of macroscopic, symbolic and molecular levels of chemical representations;

(c) employ dynamic computer-generated representations of matter at the molecular level;

(d) allow users to view, in real-time, the dynamic effect changing variables have on a physical or chemical system at the molecular level; and

(e) use a laboratory-based inquiry oriented instructional strategy at both the macroscopic and microscopic level.

Instructional materials having these combined characteristics would be unique and have great promise for facilitating learning in chemistry.

Inquiry-oriented approaches like the Learning Cycle have been shown to have advantages over traditional instructional approaches in attitudes, motivation, and concept and process learning (Lawson, Abraham and Renner, 1989). The Learning Cycle Approach is an instructional strategy originally derived from the developmental theory of Jean Piaget and the constructivist view of the nature of science (Lawson, 1995).

This strategy divides instruction into three phases. In the first phase, called the exploration phase, students are given experience with the concept to be developed. Critical to this phase is the active participation of the learner in interacting with the chemical system. This is followed by the conceptual invention phase where the student and/or teacher derive the concept from the exploration observations. The final phase, called the application phase, gives the student the opportunity to explore the usefulness and application of the concept.

Piaget’s Functioning Model

Learning Cycle Teaching Model

Inquires into Chemistry
MoLE

Assimilation

Exploration

Data Collection and Analysis

Accommodation

Concept Invention

Conclusions and/or Interpretation

Organization

Application

Open-inquiry experiment

 

The key to this type of instructional approach it that the learner derives the concept from observations of the behavior of a chemical system. One of the weaknesses of laboratory-based inquiry-oriented instruction is the difficulty of inventing a molecular explanation from laboratory data to justify experimental patterns. Students can observe pressure, volume, temperature relationships in gases, but they can’t observe the molecular behavior that explains these relationships. The instructor is left with the task of just telling the student about molecular behavior and hoping they will make the macroscopic/microscopic link.

A laboratory manual containing laboratory activities based on the Learning Cycle Approach has been developed by Abraham and Pavelich (Abraham, 1991; Abraham, 1991). The third edition of this laboratory manual has recently been published. This new edition will contain several innovative features including: format changes to make the Learning Cycle Approach more overt, the use of an introductory problem statement, and a requirement for students to build a mental molecular model to explain the observations made in the laboratory.

The proposed educational approach will have the student experience the laboratory relationships and then to do a parallel model experiment on the molecular level. At that point a concept invention on both the experimental and molecular levels would facilitate the linking of macroscopic/microscopic behavior. A unique feature of this approach, then, is the integration of the Learning Cycle Approach to computer-based simulations of atomic molecular behavior and to parallel laboratory activities.

Macroscopic laboratory experiment

A laboratory manual containing laboratory activities based on the Learning Cycle Approach has been developed by Micheal Abraham and Micheal Pavelich, Inquires in Chemistry by Waveland Press.

The organization of the macroscopic Gas Law guided inquiry experiment has the student collecting data and analyzing data at the beginning of the experiment. Then the student answers a series of questions in the conclusions and/or interpretation section. Along with discussion by the teacher the students invent the concept in this section. Then students select an extension activity in the open-inquiry experiment.

In the macroscopic inquiry experiment the student first investigates the relationship between pressure and volume using a syringe and a pressure transducer. In a second experiment the students investigate the relationship between pressure and temperature. Students collect date, look for patterns and invent a mathematical relationship between the variables.

In an effort to have the student consider a microscopic model of their experience at the end of each section students are to answer a question forcing them to think about what is happening at the particulate level for each experiment.

A. Mental Model - Draw a picture(s) that explains how the pressure and volume of a gas sample are related at the level of atoms and molecules and that illustrates the observations you made in the experiment. In words, explain how your picture(s) illustrate(s) this relationship.

B. Mental Model - Draw a picture(s) that explains how the pressure and temperature of a gas sample are related at the level of atoms and molecules and that illustrates the observations you made in the experiment. In words, explain how your picture(s) illustrate(s) this relationship.

 

Microscopic laboratory experiment

Gas Law Simulation

This guided inquiry experiment is organized along the same structure as the macroscopic experience described above. In this activity the students begin with a 2 page description of what the screen looks like and an invitation to play with/explore the different parts of the screen. After the student feels they are comfortable with the screen they are given a problem statement.

In this case the first problem statement is ‘How are the pressure and volume of a gas sample related?’ To begin the exploration the student is directed to open the simulation and observe and describe what happens in the Gas Sample window. The student is not expected to change any variables, simply to observe and describe what they observe. The student is given a list of words they should consider using in their description, words like particles, atoms, molecules, collisions, velocity, energy and force. The goal is to see how the student is able to express what they observe using those particular terms/concepts. Do the students introduce some other terms like, speed, or straight-line motion. Do they see the particles occupy a small volume compared to the container. Do they see that the particle’s energy may change after a collision with another particle, but not with the walls of the container?

The student is then asked to enable the tracking function and to trace the path of a particle as it moves from one side of the screen to the other and to explain any changes in velocity or direction they observe. In this question we are making sure the student recognizes the particles change direction and velocity when colliding with another particle, and only change direction when colliding with the wall of the container.

When one looks at the drawings student are drawing the particle using a straight line until there is a collision with another particle. Collisions with the walls of the container are drawn properly (angle of incidence = angle of reflection). Collisions with other particles show a much great variation in the direction taken by the particle. The student responses to this question are interesting, and at times you wonder how they make the observations they’ve recorded.

For example, the particle builds up speed if left alone, or hit from another particle accelerated its movement. Some students were very literal in their response. They would draw a diagram of the particle movement and identify when the particle collided with another particle or with the wall of the container and not provide any explanation of the particle behavior.

A few students actually stated the particle travelled in a straight line.

To begin the Data Collection and Interpretation portion of the experiment students are asked to record the values of each of the variables in the Control Bar window. We wanted the student to notice this part of the screen and the information provided there.

The students then performed an experiment. The experiment they are asked to do is to change the volume of the container and observe what happens to the pressure of the system. They are then asked to explain how the activity in the Gas Sample window accounts for the pressure observation.

Students clearly saw that decreasing the volume increased the pressure and visa versa. What was interesting was their explanation for the change in pressure. Many students correctly recognized that the change is explained in terms of the change in the number of collisions with the walls of the container. Some students were more vague in their explanation by saying the change is accounted for due to changes in the number of collisions among the particles. Some students missed the fact that we asked for an explanation of their observation. Interestingly a reasonable number of students explained the observation in terms of the activity, or speed of the particles.

As the volume decreases the activity or speed of the particles increase and the pressure goes up due to the increase number of collisions with the walls of the container. When the volume increases the particles slow down and there are fewer collisions with the walls of the container. Indeed when the volume of the container is decreased the particles ‘look’ like they are moving faster, but that is only suggested by the cramped conditions and the greater number of collisions between particles. Mike and I felt this particular misconception was due to the student not looking at the velocity distribution, or not understand what the distribution was saying when they changed the volume of the container.

To try to correct for this misconception we have added a question forcing students to look at this region of the screen and to relate what they see to the behavior of the particles in the Gas Sample Region. We also ask the student to sketch and label the graph they see. We hope this will make them look at the behavior of the particle speeds when different variables are changed. Hopefully they will look at this region and note there is no change in the average kinetic energy when the volume changes, therefore the particles can not be moving faster.

Continuing with the experiment students were asked to find a pattern with their PV data. Most students were able to draw a graph showing the inverse relationship between P and V. Students were even able to express that relationship mathematically. But when asked to predict the pressure at a volume greater than the volume of the container many students failed. They recognized the inverse relationship between P and V, could write a mathematical equation, but could not predict. Some resorted to using the ideal gas equation to solve the problem. Few students looked at the data table and recognized that PŠV = constant.

The next part of the experiment asked the students to see how pressure and temperature are related. Again the student was told to investigate the effect on pressure of changing temperature and then asked to explain their observations. Students in general did better on this explanation. However, most students focused on the greater number of collisions with the container walls with the increase in temperature. Fewer students noted the higher velocity mean the force of the collisions with the walls was increasing.

Testing With Students

The microscopic guided inquiry experiment was used at both the University of Oklahoma and Oklahoma State University. At OU 26 of approximately 50 students enrolled in summer school in 2000 performed the experiment as an extra credit homework assignment. They did the assignment after doing the macroscopic guided inquiry experiment laboratory.

At Oklahoma State University approximately 450 students did the microscopic experiment during the Fall 2000 semester. It replaced one of the normally scheduled laboratory experiments for the semester. The students were expected to log on to the class web site, download and print the laboratory experiment and then perform the experiment on the computer where ever they wanted. Their only requirement was to turn the write-up into me by 5:00 pm of the day of their normally scheduled laboratory. The students at OSU did not perform the macroscopic guided inquiry experiment, but they had done a verification gas law experiment where they determinethe molar mass of several gases. They had also experienced a demonstration in lecture where I used equipment similar to the equipment required in the macroscopic guided inquiry experiment to demonstrate the relationship between pressure and volume and volume and temperature.

Final Remarks

We see the Gas Law Simulation and the MoLE activities as flexible enough to be used in any of several different classroom setting. In lecture in a demonstration mode under the control of the teacher, as a homework assignment where students work indivdually answer specific questions and/or collecting data, as a laboratory assignment in a computer laboratory, at home or where ever the student has access to a computer connected to the internet, and finally as a cooperative learning activity used in a small group.

We invite anyone interested to go to intro.chem.okstate.edu to obtain the latest version of the guide inquiry laboratory experiment and to access the simulation and to use the materials in their classrooms. We certain appreciate feedback and suggestions how to make the materials more useful.

The simulation is also available at www.merlot.org under the Genreal Chemistry materials. The Merlot site also encourages reviews and comments from users.

Other Gas Law Simulations

3-D Molecular Dynamics Software 3-D Molecular Dynamics Software - Interactive physics of chemistry software by Stark Design enables students, educators and scientists to experiment with molecular-level physics, chemistry and materials science.

Boltzmann: A Kinetic Molecular Demonstrator (Randall B. Shirts, Brigham Young University) Boltzmann is designed to help students understand the principles of kinetic molecular theory by demonstrating molecular motion, statistical mechanics and other fundamental theories of chemistry and physics.

Logal Software: Simulation/tutorial software for introductory chemistry; topics include Equilibrium, Electrochemistry, The Atom, Gas Laws, Chemical Kinetics, Periodic Table, and Stoichiometry (not sure if this link is working)

Molecular Model (Ideal Gas): Shows a microscopic model for an ideal gas.

Special Processes of an Ideal Gas: Java simulation of the three basic thermodynamic processes - isobaric, isothermal, and isochoric

Kinetic Theory I: Simulation of a (two-dimensional) gas of hard spheres. Shows Maxwell-Boltzmann speed distribution, and illustrates such concepts as mean free path and irreversibility. [Note: Source code available at http://comp.uark.edu/~jgeabana/progr.html -- JW.]

Kinetic Theory of Gases: (In Spanish) Applet shows a container of particles, which represents an ideal gas. temperature, number of particles, and size of container user-defined.

Ideal Gas Transformations: This applet presents a simulation of four simple transformations in a contained ideal diatomic gas. The user chooses the type of transformation and, depending on the type of transformation, adds or removes heat, or adjusts the gas volume manually. The applet displays the values of the three variables of state P, V, and T, as well as a P-V or T-V graph in real time.

Thermodynamic Equilibrium: A simulation of the kinetic theory of gasses. Students can study the dependence of the mixing of two gasses on temperature and pressure. This material includes several virtual labs for students to perform.

Ideal Gas Law: Explore the relationships between Volume, Pressure and Temperature that form the basis of the ideal gas law and the piston.

Maxwellian Velocity Distribution: This experiment is designed to further demonstrate the properties of the ideal gas law. Mirror site: l

References:

Abraham, M. R. & Pavelich, M. J. (1991). Inquiries into chemistry (2 ed.). Prospect Heights, IL: Waveland Press.

Abraham, M. R. & Pavelich, M. J. (1991). Inquiries into chemistry: Teacher's guide (2 ed.). Prospect Heights, IL: Waveland Press.

Lawson, A. E. (1995). Science teaching and the development of thinking. Belmont, CA: Wadsworth Publishing Company.

Lawson, A. E., Abraham, M. R., & Renner, J. W. (1989). A theory of instruction: Using the learning cycle to teach science concepts and thinking skills [Monograph, Number One]. Kansas State University, Manhattan, Ks: National Association for Research in Science Teaching.