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Fundamentals

Experiments are commonly performed in order to determine the effect of one variable (the independent variable) upon another variable (the dependent variable).  When designing such an experiment, it is important to identify all possible variables that might effect the outcome on the dependent variable. Once done, hold all variables constant with the exception of the independent variable. Make systematic and controlled changes in the independent variable and measure the effect upon the dependent variable.
 

There are several versions of this question that differ only in terms of the randomized order of the answer options. Here is one of those versions:
 

Version 1:

A student lab group is brainstorming the design of an experiment that uses a gas-filled balloon to determine how the temperature affects the volume of the gas. Which Post-it note describes the most effective design?

  1. Inflate three different balloons to three different volumes. Get three different beakers and fill them with water having three different temperatures. Put the biggest balloon in the beaker with the hottest water and the smallest balloon in the beaker with the coldest water. Measure the volume of each balloon and the temperature of the water.
  2. Inflate a balloon. Put it in a beaker of room temperature water. Measure the balloon’s volume and the temperature of the water. Place the same balloon in a beaker of very cold water. Wait 3 minutes. Measure the new volume of the balloon and the temperature of the water. Place the same balloon in a beaker of heated water. Wait 3 minutes. Measure the new volume of the balloon and the temperature of the water.
  3. Inflate a balloon. Put it in a beaker of water. Measure the volume of the balloon and the temperature of the water. Inflate a different balloon. Put the balloon in the same beaker and measure volume and temperature. Repeat the procedure for a third balloon. Make sure that each balloon is inflated to a different volume each time you blow into it.
  4. Inflate three different balloons so that they have different volumes. Prepare three beakers with water having a different temperature. Place the balloons in the water. Measure the volume of the water in the beaker and the temperature of the water in each beaker.

 

How to Think About This Situation

You are going to have to do some reading here. As you read, make sense of the words. You are looking for a procedure that is going to allow one to determine the effect that changes in the temperature will have upon the volume. Such a procedure will be careful to keep everything constant and controlled except for the temperature. And from trial to trial, the volume will be measured. 

Bad experimental designs will fail to control other variables besides the temperature or will fail to measure the volume. So read carefully and eliminate the poor designs and select out the design that isolates temperature as the independent variable and the only variable that is changed.
 

Sorry.  We're pedaling as fast as we can but as of this writing we do not have any Tutorial information on the topic of experimentation and variables. 
 


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