Physical Science

Experiment 1-2

Background Information

Carefully observing with the unaided senses as in Experiment 1-1 is a valuable skill.  But it is often desirable to extend what the senses are capable of detecting alone.  Measurement adds capability to the senses.

Most people have the idea that quality science education requires lots of expensive apparatus.  Sometimes expensive apparatus is helpful.  But often fancy equipment just gives the illusion of quality science.  More often than might be imagined, real scientists have to design and build their own apparatus to investigate beyond the frontier of what is known.  That is because off-the-shelf commercial equipment typically can only measuring regions already known.

Even if you have expensive equipment to measure volume, it is a valuable challenge to attempt to design and build some measurement equipment.  Learning to design, build, calibrate, and test the equipment may be more valuable than the actual equipment itself.  That knowledge will be useful even when working with fancy, expensive equipment.

There are more than two ways to measure volume:

measure dimensions and calculate using a formula.  (This is usually taught as a part of mathematics.  We will use this when simplest.)

use a calibrated measuring container.  In this experiment we will construct such a device.

Procedure

Design, build, calibrate, and test a graduated cylinder.  A graduated cylinder works because the top surface of the liquid, called the meniscus, is noticeably higher with more liquid.  The effect is better if the container is tall and narrow.

1. Find a tall, skinny container: small for measuring small volumes or larger for bigger volumes.
2. Figure a way to write scale marks on the side.
3. A primary standard is needed to calibrate your new cylinder with appropriate units.  This could either be another reliable graduated cylinder, a folded paper box [say one centimeter on each side], or a measuring spoon.  The toughest part will be to CAREFULLY transfer measured amounts of water from the primary standard to the new cylinder, then CAREFULLY marking the lowest part of the meniscus over and over reliably.  You device will be much more useful if you choose a unit that is a standard such as cm³.
4. Create three methods for testing your new graduated cylinder.  Three characteristics needing testing are:
   • The precision of the cylinder is how close are repeat measurements of identical volumes. 
   • Accuracy is how close a measurement is to the true volume.
   • The sensitivity indicates how much of a volume change is needed to be detected as different.

Record your results in your science journal and write a formal report to earn credit.