Materials:

Blocks (At least 16 blocks per group); Box (Suitable to hold several blocks);

Beaker (Large enough to hold several blocks); Ruler; Balance

Strategies:

The following story contains several dilemmas. Each dilemma can be solved by

an equation based on your knowledge of measurement, and your knowledge of the

physical properties of matter.

STORY:

A young mother, wanting to keep up with the number of blocks her plays with in

his room decides to keep a daily count of the total which is sixteen blocks. All

of the blocks are the same size and shape. In order to keep up with the number of

blocks her son has, she develops the following equation: Number of Visible Blocks

= 16. The total number of visible blocks is constant with the number 16. So this

would be a true equation.

The above equation works fine for a while, until one day she counts the

number of blocks and finds that there are only fourteen visible blocks in the

room. The mother searches the room thoroughly but she cannot find the missing

blocks. The frustrated mother is about to give up when she notices a trunk (box)

under her son’s bed. She becomes even more frustrated when she finds out that the

trunk is locked and her son does not have a key. So she waits for a day when she

can account for the total number of blocks and revises her old equation? Remember

the total number of blocks is sixteen. Your (the mother’s) equation is:

_____________________________________________________________________

This equation works fine for a while, until the mother takes another look

around the room and notices a large pail(beaker) filled with a green, murky

liquid. She does not want to stick her hands into the liquid to find out if the

pail contains the missing blocks so she again revises her old equation. One

observation she makes is that the liquid measures about half full in the pail.

How can the mother determine if the blocks are in the pail? Experiment as before,

then revise the second equation. Remember the total number of blocks!

This equation, too, works fine for a while, and she is thoroughly convinced

that she has looked everywhere, when she happens to look out of the window.

There, she notices two blocks on the lawn. So she adds these blocks to the total

count and revises her equation again. OOPS! What do you believe has happened

here? Can you develop an equation that would prove true for the mother? HINT:

No blocks can be created or destroyed! Teachers: This experiment can be expanded

to include the following concepts: 1. The relationship of mass vs. volume. 2.

Density, specific gravity problems. 3. Law of the Conservation of Mass or Atoms.

The main idea of this lesson is to emphasize conservation. Many topics

covered in Chemistry (i.e. balancing equations, energy exchanges in chemical

reactions, etc.) requires that this concept be understood. Yet, too many times

the student does not understand, leaving large gap when introducing a new concept.

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Rob Duncan

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