## Thursday, January 28, 2016

### Introduction and background

After I have taught/reviewed the scientific method with my students, we do a lab using Hot Wheels cars to give them practice using the scientific method.

The question they are trying to answer is: On which surface will my Hot Wheels car roll furthest after going down a ramp: 60 grit sandpaper, carpet, or cedar fencing?
You could do this lab with any number or type of surfaces that you choose.  Also, depending on the time you have and resources available you could let the students completely design the experiment, coming up with the surfaces and the set-up.  If this is the case, you could reword the question to: On which surface will my Hot Wheels car roll furthest after going down a ramp.

For our lab, due to time constraints, I have designed the initial set-up of the lab and the surfaces for the cars.

### The Lab

The purpose of the lab is: To show understanding of the scientific method by designing a lab sheet (and possibly the lab itself), completing the experiment, then analyzing the data and reporting on the lab.

After showing the students the initial set-up, I have the students use a word processor to design a lab sheet that includes the following headings:
• Problem/Question
• Hypothesis
• Independent and Dependent Variables
• Constants
• Procedure
• Data
• Analysis
• Conclusion
The students need to have information under each heading through the Procedure as well as a data table that they can fill out during the experiment done and printed out before I will let them proceed with the experiment.  An example may look like this.

#### Hot Wheels Scientific Method Lab

Problem/Question
On which surface will my Hot Wheels car roll furthest after going down a ramp: 60 grit sandpaper, carpet, or cedar fencing?

Hypothesis
My hypothesis is that the Hot Wheels car will roll the furthest on the 60 grit sandpaper.
Independent and Dependent Variables
The independent variable in this experiment is the surfaces the car is traveling on.  The dependent variable is the distance the car goes.
Constants
Some things that need to remain constant are:
The car I use.
Where/how high the car starts on the ramp.
How I release the car.
How I measure the distance including to the front or back of the car and the units I use.

Procedure
Line the back of the car up with back edge of the track.  Without pushing the car, release it so that it rolls down the orange track.  Let it roll on the surface until it comes to a stop.  Measure from the end of the orange track to the back of the car and record the distance in centimeters.  Repeat 5 times for each surface.  Use the same car for each trial and each surface.

Data

Analysis

Conclusion

Once they have this much done and printed out, I let them start the experiment.  They should record the data on in their table.  When they have finished the experiment, it's back to the computer for them to do their analysis and write up their conclusion.  When the lab paper is finished I have them print it out and turn it in.

### Notes

• Remember, this lab is not really about what surface the cars go further on.  The students are not graded on getting the "right" surface.  It's about the scientific method.  How well did they organize their lab sheet?  How well did they pay attention to the constants.  How well did they perform the procedure.  How well did they analyze the experiment and discuss the problems.  These are the things that I pay attention to and grade them on.
• The set-up I used is not perfect by design.  I like that there are problems with the set-up and hope that the students notice these and address them in their analysis and conclusion.  One of the potential problems is that on the wood and the sandpaper, sometimes the cars veer off the surface.  The most common ways the students try to deal with these are to just do more trials until they get their specified number on the surface; or they will put "railings" on the edge to keep the car on the surface. Hopefully they realize that rubbing on their "railing" will cause the car not to go as far and perhaps skew their results.  I usually don't talk to them about this, but do look to see if they discussed how their solution may have affected their data.    Using yard sticks to guide the cars
Another issue with the experiment is that I've taped several pieces of sandpaper together.  Where they come together the seams aren't always smooth and sometime there are little ridges.  That could also affect their data.  Again, I don't talk to them about it.  I just watch to see if they notice.    There are a few other small possible problems with this set-up, but the key is, do the students notice, what if anything do they do to solve them, and most importantly, do they talk about them in their analysis and conclusion.  This is how they learn about experiments and what make a good one.
• Make sure that all the constants listed are addressed in the procedure.
• I don't mention how many trials they should do.  I let them decided.  This let's me know how well they understand the scientific method and how important multiple trials are.  I always have a few who only do one trial.  Most do 2 or 3.  Once in a while I get students who will do 5 or more.