gator science

active adventures in lower school science

Holiday Mixture

on December 16, 2013

The Second graders studied liquids today in the lab.  I asked the students to predict whether a small candle would float or sink in two different beakers filled with liquid.  Some thought the wax candle would float, while others thought the wax candle would sink.  Well, everyone was right, as the candle sunk in the alcohol and floated in the water.   A number of my students figured out there must be two different liquids in the beakers.

Our next challenge was to stack three different liquids inside a small capped bottle.   I dyed the water a red color and dyed the rubbing alcohol a green color. The corn oil stayed a golden yellow color.  The dense red water sank to the bottom.  The less dense corn oil sat on top of the water and the least dense green alcohol floated on top of the corn oil.   I asked the students to shake all the contents in the bottle.  At first there was lots of oily bubbles floating in the mixture.  After we waited awhile, the mixture separated into two distinct parts.  We discovered that the oil separates and floats on top since it is less dense.  The water and alcohol mixed together because they are similar materials chemically.  Since oil is not similar chemically to alcohol and water, it does not mix.

Like Dissolves Like

Students also experimented on our own.  Some students changed the order of when you added the liquids to the bottle.    A number of students flipped the capped bottle to see the oil flip inside the bottle like a lava lamp.   Some students found a purple color when they added more water and a green color when they added more alcohol.   One of my favorite analogies was that since alcohol and water are friends, they mix together easily.  Which reminds me of the saying, “those two mix together like oil and water.”

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