Acids & Bases

Acids and Bases:  What happens when H+ ions dissociate

Today was all about acids and bases.  Students put on their safety goggles and investigated how scientists classify acids and bases using the pH scale.   The lesson began by teaching our young scientists about ions, an atom that loses or gains an electron. Once atoms become ions and are charged, they can attract or repel each other, like magnets. This is how acids and bases react. We introduced the pH scale, so they understood how scientists measure the acidity or basicity of a solution.

After learning a few basics about acids and bases, students tested the pH of 6 household solutions using indicator strips and compared the actual pH with the previously predicted pH. The young scientists were shocked to discover that some solutions were extremely acidic or basic and found that soda is very acidic–sugar isn’t the only reason it is bad for your teeth!

We also performed several demonstrations for the students today.  In one demonstration we used red cabbage juice as an acid/base indicator. The dark purple color in the cabbage comes from a pigment called anthocyanin, which changes color depending on pH.  Acids made the purple juice from the red cabbage turn red, while bases made the purple juice turn green.  We also discovered what happens when you mix an acid (vinegar) and a base (baking soda) together; the reaction results in water, a salt, and carbon dioxide bubbles!  Our final demonstration showed the corrosive nature of strong acids (and bases).  We put aluminum foil into a beaker of Hydrochloric Acid (HCl).  After a few minutes, the Aluminum starts to break down, releasing Hydrogen gas, which can be used to produce a barking sound when collected and ignited in a test tube!

 

 

Additional Information:

This is an AWESOME video about what happens to an “aluminium” coke can in a strong acid (HCl “hydrochloric acid”) and a strong base (NaOH “sodium hydroxide), the same liquids you saw today!

http://www.youtube.com/watch?v=WnPrtYUKke8

 

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