Measurement of Volume 

Richard Murray                 Gage Park High School
                               5630 South Rockwell
                               Chicago IL 60629
                               (312) 535-9230

Objectives:

This mini teach is for middle school and high school students.  It can be 
adapted for younger children as a demo. 

Students will be able to measure the volume of a clear container.  Students will 
be able to use a stop watch.  Students will be able to estimate the volume of a 
container using proportions. 

Materials Needed:

Clear jars, glass or plastic, enough of them so that every group of students 
will have two containers to measure.  Enough sand to fill the largest container. 
Measuring bowl and cup marked in milliliters; candles and matches; stop watches 
for each group. 

Strategy:

What was expected was a linear relationship between the burning of oxygen in the 
jar and volume of air that it contained.  If it is linear it will be 
predictable.  Knowing how long it takes to extinguish a candle for a certain 
volume you should be able to predict either the volume and or the time to 
extinguish a candle for another container. 

The students will time how long a candle will stay lit when a jar is placed over 
the candle.  The student will measure the volume of the jar by filling it with 
sand and using the measuring bowl or cup to find out how much sand is in the jar 
in terms of the metric system.   

Students will then time how long a candle will stay lit in a much larger 
container.  Knowing the previous data regarding volume and time and now knowing 
the time for this new jar the student should now be able to predict the volume 
of the second jar.  The prediction is developed through proportions.  The ratios 
that make up the proportion are: volume is to time as second volume is to second 
time.  Restating the problem, the proportion will look like:  volume in ml/time 
to extinguish the candle = unknown volume of the new jar/time to extinguish the 
second candle. 

Solving the proportion the student will have the predicted volume.  To verify 
the prediction the student will measure the volume of the second container using 
sand.  The student will determine how close the prediction is to the actual 
measurement. 

Performance Assessment: 

The linear relationship that was expected was not produced by this procedure.  
It was not established that there is linear relationship.  The predictions for 
the larger jar were off.  If the time was measured for the larger jar then 
predicted volume was larger then the actual measured volume.  If the volume of 
the larger container was measured then the predicted time differed greatly from 
the actual time. 

Sources of error are pressing the stop watch (timing errors), the candle is not 
burning at a constant rate, a larger flame burns oxygen at a greater rate;  
errors using the measurement bowl; the jars need time to refill with oxygen, if 
you try to repeat the timing of the burning candle too soon the results will 
vary as much as 4 to 5 seconds. 
 
It was a good lesson in measuring, timing and  gathering data.  But it did not 
support the hypothesis.  Because the hypothesis is not supported then it creates 
a problem for the students.  The expectation is that the goal should be achieve 
and it wasn't.  This is a problem that will need to be addressed with the 
students.  

Things that could be tried to improve the results are:  work with larger volumes 
such as storage cases instead of jars; the candle be replaced with a source that 
burns consistently such as of oil with a wick.