Acids

Acid is a chemical term that means a substance with a pH higher than 7. pH is determined by the number of Hydrogen ions formed when a chemical is dissolved in water, the more H ions, the higher the acidity. The further a chemical is from neutral, the more harsh it is.

Seven is neutral; distilled water is neutral. Some common familiar acids are vinegar, soda pop, rain water (not necessarily “acid” rain, all rain water is naturally acidic), and citric acid (found in lemon juice and orange juice, etc.).

Penny Acid Experiment

A very simple acid demonstration is to take some pennies, place them on a paper towel soaked in vinegar (an acid). See what happens after a day or two. The pennies will turn green as the copper reacts with the acetic acid (the chemical name for vinegar).

How to oxidize pennies with vinegar and salt.

Let your kids experiment with other chemicals to see if they have the same effect or a different effect on the pennies. Be careful not to mix chemicals. Do a separate plate for each chemical you experiment with.

Soda Pop Acid Experiment

This works great for when you have a child losing teeth. Take a tooth and place it in a cup with some soda pop, cola works best, let it sit and check on it every day for at least 2 weeks. What happens to the tooth? Try setting up a second experiment with another tooth in plain sugar water. What effect does the sugar water have on the tooth vs. the cola.  Soda pop is very acidic.

Green Goo Acid Experiment

Get some steel wool, put it in a small jar, then pour vinegar over the steel wool, let it soak for a week. It’ll turn really gross and brown and this for some unknown reason makes kids happy.

Then take the steel wool out of the jar and add ammonia to the vinegar mixture. The mixture immediately turns into a greenish gel.

The vinegar, an acid, chemically reacts with the steel (which contains iron) to make iron acetate. Next pour 1 T. ammonia (ammonium hydroxide) into the iron acetate. The iron acetate reacts with the ammonium hydroxide to make ammonium acetate and iron hydroxide.

iron acetate + ammonium hydroxide —-> ammonium acetate + iron hydroxide

All the original ingredients are still present, but it makes a totally different substance.

Additional Layers

  • Why are strong acids like vinegar used to preserve foods? What do acids do to living things?
  • What rots your teeth more? Is it sugar, or is it acids? Bacteria in your mouth eat the food left over. The metabolism of the bacteria produces acids that are the cause of tooth decay, not the food or sugar directly, but you still have to brush your teeth. Sugar is a favorite food of bacteria, easily broken down and used. Have older kids research to find out what chemicals in tooth enamel and cola form the reaction that cause that cavity.
  • Get some acid indicator paper and experiment around the house to discover what chemicals are acids, and which are neutral or basic. All chemicals must be liquid or dissolved in water to be tested.
  • Learn more about acid rain. What causes it and where is it a problem? What kinds of damage does it do? What can be done about it?
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