Chemistry

Experiment A-4

In experiment A-2 you attempted to create a classification system for a set of observed chemicals.  You may have found the task rather challenging and for good reason.  In his classification of different cognitive thinking skills, educator Benjamin Bloom (1913-1999) identified in 1956 that creating a classification system is one of the more complex thinking processes.  Jean Piaget (1896-1980) proposed a number of developmental stages by which each human being develops the ability to think and reason from motor reflexes at birth to potentially using symbols to represent abstract concepts.  But Piaget noted that only 35% of high school graduates in industrialized countries reach the fourth, formal operations stage of thinking and many adults don't ever think formally.  This could be a difficulty for some people trying to learn those parts of chemistry which are rather abstract.  However the constructivism theory suggests that if appropriate experiences occur, one can develop those thinking skills and understanding.  This study of chemistry is designed to provide such experiences to develop chemical skills and understanding.  So while some of these experiments such as A-2 seem difficult, remember that they have been designed to challenge and grow your skills.  In Experiment A-5 we will further study useful classification systems.

But first we wish to review and develop observations using quantitative measurements.  While our unaided senses will continue to be valuable, measurements provide details that might reveal key insights.  Measurement adds capability to the senses.  Typically measurement require tools that have one or more scales which have been calibrated by comparing with accepted standards.  Measuring volume often involves a container calibrated in three dimensional units such as cubic centimeters (equal milliliters).  Mass typically is measured by using a balance which compares the unknown object with multiples of a standard mass such as a gram.

Humans have used mass and volume as alternative properties for measuring objects for a very long time.  Mass and volume have different advantages and disadvantages.  But in this experiment we wish to compare the numerical values for several examples each for several kinds of substances.  One of the more useful ways to make such a comparison is to construct a graph so any pattern may be visualized.

Equipment

• Balance to measure mass:  It may have a spring which expands or compresses or it may work like a teeter-tauter.  If necessary you could make a balance.
  
  
• Graduated cylinder to measure volume:  This is basically a measuring cup with a scale marked on the side indicating the amount of contents.  You could make such a graduated cylinder.

Procedure

1. Obtain several samples of materials made of iron or steel such as nails or screws.  Obtain enough so you can measure the mass and volume of some of the sample.
   1. Accurately measure the mass of the selected sample.
   2. Use displacement of a liquid (such as water) to measure the volume of the sample. 
      1. (That is, measure the volume of enough liquid to later cover the sample,
      2. add the sample to the liquid and measure to total volume,
      3. subtract the liquid volume to find the volume of the sample.)
   3. Significantly change the amount of material in the sample and repeat the above, measuring both mass and volume.
   4. Change the amount of material again and repeat the procedure of determining the sample's mass and volume.
2. Obtain a measurable sample of aluminum (perhaps aluminum foil) and repeat the procedure obtaining mass and volume for at least three samples.
3. Obtain a third type of material, preferably not a metal, and determine the mass and volume for at least three samples.
4. Construct a graph showing the mass (vertical axis) verse volume (horizontal axis) for each sample.

If you need course credit, use your observations recorded in your journal to construct a formal report.

Reference