My physics colleagues Frank Noschese and John Burke have invited physics and math teachers to contribute a posting that exemplifies the concept of pseudoteaching [PT]:
Pseudoteaching is something you realize you’re doing after you’ve attempted a lesson which from the outset looks like it should result in student learning, but upon further reflection, you realize that the lesson itself was flawed and involved minimal learning.
Laboratory work is essential in the sciences; after all, don't we want our students to have a first-hand experience of thinking like scientists?
Why then are ‘cookbook’ type of labs ubiquitous?
During my first years of teaching this is how I did labs in my physics classes:
a. I had all the equipment neatly set on the lab tables.
b. I divided my students into teams.
c. I provided each of them with a worksheet with step-by-step lab directions.
When observed by my immediate supervisor I always got praised by how well I conducted the lesson. After all it was evident that the students were engaged. Perhaps they were busy, but were they learning?
Let’s take a closer look at this example of a traditional cookbook type lab:
MASS-SPRING SYSTEM
I. OBJECTIVE
The objective of this lab is to determine the spring constant for a spring using two methods.
II. EQUIPMENT
Ring stand, Mass set, Spring, Meter stick, Stopwatch
III. PROCEDURE 1
1. Hang the spring from the ring stand.
2. Place the meter stick vertically and record the position of the bottom of the spring. This is the unstretched length.
3. Attach a mass on the spring so that it will stretch the spring and hang at rest.
4. Measure the new position and record it in the Data table.
5. Measure the displacement for 5 different masses added to the spring.
The displacement is the difference between the unstretched length and the stretched length. Record your measurements in the Data table.
IV. ANALYSIS
1. Construct a graph of Force (N) vs. Displacement (m).
2. Determine the slope of this graph.
3. What are the units for the slope?
4. The equation relating the magnitude of the force and the stretch is F = -kx . How does this equation relate to the slope of your graph?
V. PROCEDURE 2
1. Remove the spring from the hanger and measure its mass and record it on the table.
2. Hang the spring from the ring stand.
3. Attach a 100 g mass to the spring.
4. Stretch the spring about 5 cm and let it oscillate up and down.
5. Use your stopwatch to measure 10 complete oscillations. Divide this number by 10 and record it as the period on the data table.
6. Measure the period for 5 different masses added to the spring. Record your measurements in the Data table.
VI. ANALYSIS
1. The total mass of the system is given by adding the hanging mass plus one-third of the mass of the spring. This is called the effective value of the mass.
2. Use the period equation to calculate the spring constant for each of your trials.
VII. CONCLUSIONS
1. How do the values of the spring constant compare with both methods?
2. Calculate the percent difference.
So, what is wrong with this lab?
From the lesson perspective apparently nothing is wrong with it. The lab provides guidance to the student for determining the spring constant with two different procedures. The lab includes data collection, the students graph their data, they follow prompts to analyze the graph and answer a couple of questions as a conclusion. They must have learned how physics works in the real world!
Wrong!
The students just followed a recipe and completed a worksheet. They were told what to do and how to interpret the data. Completing this worksheet does not provide evidence of critical thinking at all!
What actually happened is that the students were robbed of the opportunity to do real science! It would be more effective to let them design their lab, make their own decisions about collecting and analyzing their data, and investigating the sources of error and uncertainties in their measurements.
I believe that it is by doing science that actual learning occurs. I've found that a better way to conduct this lesson is by making it an open-ended investigation. In this type of inquiry labs the students are given a task for the experiment but have significant latitude in terms of what procedure to follow, which measurements to take and how to conduct their analysis. The students record their findings in a lab journal including the following items:
I. Purpose
Write a statement of the problem to be investigated that provides the overall direction for the investigation.
II. Hypothesis and Prediction
State a hypothesis and a prediction for your experiment as appropriate.
III. Equipment and Equipment Setup
- A list of all laboratory equipment used in the investigation.
- A detailed and labeled diagram to illustrate the configuration of the equipment.
IV. Step-by-Step Procedure
- Neatly explained, preferably in a numbered sequence.
- Identify and name all experimental variables and describe how the independent variable is controlled.
V. Data
-What data needs to be taken?
- How many trials do you have to include?
- How is data reported?
VI. Data Analysis
- How do you interpret data?
- Include graphs and analysis of graphs as appropriate
- How do you compare the results obtained by two different ways?
VII. Conclusions
- Discuss any questionable data or surprising results.
- Explain the possible source of any error or questionable results.
- Suggest changes in experimental design that might test your explanations.
Nowadays when doing a lab about this topic, all my students receive from me is this prompt:
"Design and conduct two different experiments to determine the spring constant of a mass-spring system."
What actually happened is that the students were robbed of the opportunity to do real science! It would be more effective to let them design their lab, make their own decisions about collecting and analyzing their data, and investigating the sources of error and uncertainties in their measurements.
I believe that it is by doing science that actual learning occurs. I've found that a better way to conduct this lesson is by making it an open-ended investigation. In this type of inquiry labs the students are given a task for the experiment but have significant latitude in terms of what procedure to follow, which measurements to take and how to conduct their analysis. The students record their findings in a lab journal including the following items:
I. Purpose
Write a statement of the problem to be investigated that provides the overall direction for the investigation.
II. Hypothesis and Prediction
State a hypothesis and a prediction for your experiment as appropriate.
III. Equipment and Equipment Setup
- A list of all laboratory equipment used in the investigation.
- A detailed and labeled diagram to illustrate the configuration of the equipment.
IV. Step-by-Step Procedure
- Neatly explained, preferably in a numbered sequence.
- Identify and name all experimental variables and describe how the independent variable is controlled.
V. Data
-What data needs to be taken?
- How many trials do you have to include?
- How is data reported?
VI. Data Analysis
- How do you interpret data?
- Include graphs and analysis of graphs as appropriate
- How do you compare the results obtained by two different ways?
VII. Conclusions
- Discuss any questionable data or surprising results.
- Explain the possible source of any error or questionable results.
- Suggest changes in experimental design that might test your explanations.
Nowadays when doing a lab about this topic, all my students receive from me is this prompt:
"Design and conduct two different experiments to determine the spring constant of a mass-spring system."
What are the advantages of doing this type of investigations versus traditional ones?
Here are a few:
- Open-ended investigations eliminate the busy work component of “take the data and run” approach
- Students develop a sense of ownership and vested interest in their own learning
- Motivates students to create investigations with real-world applications
This link to my physics website has over 50 prompts for Physics Open-Ended Labs.
Arnold Arons said:
“The problem is to provide students with enough guidance to lead them into thinking and the forming of insights but not so much as to give everything away and thus destroy the attendant intellectual experience.”1
Arnold Arons said:
“The problem is to provide students with enough guidance to lead them into thinking and the forming of insights but not so much as to give everything away and thus destroy the attendant intellectual experience.”1
Amen to that!
1 Arnold Arons, "Guiding Insight and Inquiry in the Physics Laboratory", The Physics Teacher, Vol 31 May 1993