Tuesday, February 22, 2011

Pseudoteaching: Laboratory Experiments


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 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


Amen to that!

1 Arnold Arons, "Guiding Insight and Inquiry in the Physics Laboratory", The Physics Teacher, Vol 31 May 1993


9 comments:

Frank Noschese said...

Hi Dolores,

Thanks for this great post! Open-ended labs are key. I don't even give lab handouts anymore. It's sad to look back at the "pretty lab packets" I created in my first 5 years of teaching and think of all the time wasted.

Was it really wasted? Or did I need to go through that process to be a better teacher?

Many thanks,
Frank

dgende said...

Thank you for your comment Frank!
I do not think that you 'wasted' your time at all as you were able to reflect upon the value of using the lab packets.
Unfortunately it is very common to see teachers being misguided by the good grades obtained by their students in these types of labs and equating them to authentic learning.
It is only by doing this type of exercise i.e. the premise of pseudoteaching that deeper learning and transformation can occur.
Thank you for creating the thread!

scmorgan said...

Dolores, you always manage to pose not only the philosophical question but the specifics to help us learn. Thanks for sharing this example, which we can apply to other disciplines as well (I'm thinking teaching formulaic writing).

gasstationwithoutpumps said...

I'm helping another faculty member redesign the labs for a course that neither of us teach but both of us are unhappy with. (He'll probably be teaching it next year, since the department chair has just found out how bad this core course has been taught.)

The labs have been basically ignored by the faculty in the past, run by TAs who have little or no teaching experience. The lab handouts were cookbook-style, but badly written, so no one knew what they were supposed to be doing or why. Last quarter, one of the 5 labs ended up being a demo by the TA, because there wasn't time for the lab. This was in a core engineering course.

The two of us doing the redesign are in agreement that the labs should all be design exercises. That is, the students should be given a set of design specs and required to come up with a design that meets them. The lab handout may give a few hints at solutions, but the main part should be specs so clear that they allow the students to determine when they have succeeded.

Chris said...

This is wonderful Delores. I totally agree that when you give students the opportunity to direct their own learning, they are more vested and the actual learning that happens is more meaningful. I am curious as to how students react at first when you give them such latitude. Do you see any reluctance or fear of failing? If so, how do you respond?

dgende said...

Thank you for your kind comments Chris.

I start with open-ended labs with my Honors Physics class during the first week of school so the students get used to this method early in the course.

I found that a good strategy at the beginning is to give them the task and the equipment that they could use. That lets them figure out what can be measured with each piece of equipment (time with a stopwatch, length with a meterstick and so forth). As we proceed throughout the year I let them choose their equipment. Some kids do really well using technology so they can use probes for data collection but I don't want to force them into a canned lab.

I've found that what they value the most is their ability to design their own procedures.

We have post-lab discussions and they learn that more often than not things don't go the way they predicted it but they get an opportunity to revise their models. This is the way science is done and there is nothing wrong with 'failure' as long as they are able to identify what went wrong.

mmmcewen said...

Dolores,
Thanks for suppgesting such an open-ended prompt. I am changing the trimester lab exam this year and will use this approach. What a great blooger and colleague you are!
MMMcEwen

Buy Essays said...

Thanks for sharing your experience .Keep up the great work.

Term Papers said...

Love your blog and thank you for sharing it with me. Your writing style has an infectious (in a good way) feeling of life, laughter and energy that makes me smile. I can’t help but smile, when i read it.Good link!! Like it..

Post a Comment