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This lesson focuses on the conservation of energy




8, 9, 10  


By – Rob Duncan
Primary Subject – Science
Secondary Subjects –
Grade Level – 8th to 10th
To demonstrate the law of the conservation of energy (blocks) without counting
the units of energy directly.

Blocks (At least 16 blocks per group); Box (Suitable to hold several blocks);
Beaker (Large enough to hold several blocks); Ruler; Balance

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.

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.

E-Mail Rob Duncan !

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