Lesson Plan #:AELP-SPS0003

Looking at Variables

An Educator's Reference Desk Lesson Plan

Submitted by: Jean Kyle, Blossom Gulch, Coos Bay, OR
Endorsed by: These lesson plans are the result of the work of the teachers who have attended the Columbia Education Center's Summer Workshop. CEC is a consortium of teacher from 14 western states dedicated to improving the quality of education in the rural, western, United States, and particularly the quality of math and science Education. CEC uses Big Sky Telegraph as the hub of their telecommunications network that allows the participating teachers to stay in contact with their trainers and peers that they have met at the Workshops.

Date: May 1994

Grade Level(s): 4, 5, 6

Subject(s):

Overview:

This lesson, using sugar cubes and water, exposes students to the variables (manipulated/independent, responding/dependent) found in scientific experimentation. Students will use controls to be sure they are testing only certain independent variables. Students will be using good experimental design as they test each of their guesses (hypotheses).

Purpose: The purpose of the lesson is to show students that, when doing experiments, scientists must be sure that the experiments are reliable and the results are valid. They must eliminate or test all variables that can effect the results of an experiment.

Objectives:

  1. Students should be able to understand the following terms: reliable, valid, hypothesis, independent variable, dependent variable, control.
  2. The students should be able to use experimental design--Predict, Test, Observe, Hypothesize.
  3. Students should become critical observers of other experiments in terms of what is necessary for an experiment to be reliable and the results to be valid.

Resources/Materials:

  1. Lots of sugar cubes
  2. hammer for smashing cubes
  3. 4 plastic party glasses for each group
  4. paper towels or sponges
  5. variety of spoon sizes,
  6. thermometers, rulers, stopwatches, etc.

Activities and Procedures:

First, each group of three should be given 4 sugar cubes, 4 clear plastic party glasses, and 2 spoons. Explain that each group will dissolve each cube of sugar in the glasses. In one glass there will be a cube and water, one will have a cube, spoon (stirred), and water, another will have a smashed cube and water, and the last will have a smashed cube, spoon (stirring), and water. "Students predict which container will have the fastest rate of dissolving." Students need to be reminded to have a way to start all stations together or time each (stopwatch) individually. Let them at it!!

Secondly, now that a mess has been made, and everyone is wondering if anything can possibly be learned from this activity, clean up and prepare for processing, instruction, and brainstorming. Talk about predictions (it's okay to have wrong predictions--happens all the time), graph the results of the experiments. Are there different results? Were all the methods of experimentation the same? Can we hypothesize using our data? Was every group's water the same temperature (even within the group)? Did everyone stir at the same rate? Was there equal amounts of water in each glass? Could any of this make a difference?

Now is the time for instruction regarding reliability, validity, independent and dependent variables, and controls.

Brainstorm a number of manipulated/independent variables that could have had an effect upon the results of our experiment (the rate of dissolution). Put suggestions on a chart and have the groups test each variable against a control to see if it has any effect on the rate of dissolving. This may take more that one day. Teacher's job is to make sure supplies are available. The chart may look like this:

Independent Variable Prediction Exp. Notes Observation
spoon size . . .
amount of water . . .
water temperature . . .
placement of spoon . . .
extra agitation . . .
old vs. new cubes . . .
different solvents . . .

After the experiments have been completed, data may be compiled from the groups. If there is a question of validity, go back and re-test. Again, process the activity using the important vocabulary words.

Tying it all Together:

Again, alert the students to the sometimes enormous amount of variables that can have an effect upon the many experiments which scientists perform. We must strive for "pure" experiments for reliability and validity. Using the data from the preceding experiments, have the groups develop the "ultimate (fastest) sugar dissolving system.