### Controlled Experiments

greenspun.com : LUSENET : Middle School Science : One Thread

Hi everyone. I'm starting off the year with experimental design and I wanted a simple controlled experiment idea. Something that I can do in one period and doesn't involve too much prep or materials.

I know Mike gave us great internet sites but I figured most of you have experience with this and could help me out.

Thanks.

-- Deanna (zapatad75@msn.com), September 07, 2003

Deanna:

I introduce experimental design in 3 stages. Start with a simple "system" such a pendulum that has multiple variables that can be manipulated. A ball & ramp (pushing a cup at the bottom, as in the NY State Grade 8 Exam) works just as well, and in life science seed germination works but takes longer. You should be able to think of lots of other ideas depending on your curriculum.

I'll use the pendulum as an example, because I will be using it this year to teach both experimental design & conservation of (mechanical) energy. In that case, I will begin by asking students to observe & describe the motion of the pendulum, prompting them as necessary to look for specific aspects of the pendulum's movement, forces acting on it, etc. The ultimate goal will be to have students identify the potential & kinetic energy at different points along the pendulum's swing and determine where all the energy went once the pendulum is at rest - that's the content. I also want them to hypothesize about things we can manipulate to alter the swing, specifically the pendulum's "period," which is the time it takes to make one full swing - from one one extreme to the other extreme & back again to the original position. That will be our experimental design.

Since there are three obvious variables to manipulate - mass, angle of release, & length of string - we will do three separate experiments. Experiment 1 will manipulate the mass. I have a worksheet that asks experimental design questions using everyday language instead of scientific terminology, and guides the students along the way. Stage 2 manipulates the angle of release and introduces scientific terminology but includes the everyday language as well. In stage 2 I also ask students to figure out more of the design for themselves. Stage 3 manipulates the length of string, uses scientific terminology exclusively, and asks students to design most of the experiment by themselves. You can download my worksheets and change them for your own needs from: