Saturday, July 14, 2012

Experiment 3: Acids & Bases

For today's experiment we will be doing some kitchen chemistry. It's super easy and fun for kids of all ages! Experiment - Determining pH

What You Need-
  • Some Red Cabbage
  • Lemon Juice,
  • Baking Soda,
  • Cola,
  • Water,
  • Vinegar
  • Oil,
  • milk of magnesia (if you have it on hand)
  • PH chart (like the one found )
  • Medium sized bowl
  • Grater
  • Strainer
  • Clear cups
  • Some plastic containers
  1. grate some cabbage into the medium sized bowl
  2. Cover cabbage with cold water and allow it to sit for 45 minutes.
  3. Strain the water mixture into a plastic container
  4. Pour an equal amount of juice into the cups
  5. Add 1 tsp to all but one of the cups. Mix. This should turn the mixture blue, as baking soda is a base.
  6. Add lemon juice to one of the blue cups, a little at a time. How much do you need to add before bringing the color back to normal?
  7. repeat #6 for each of your other liquids. One in each cup. If the liquid remains blue, then your substance is a base. But you should notice different liquids require different amounts to change the color back to normal.
We use red cabbage because the chemical makeup of the juice allows it to dramatically change color when mixed with other substances. This makes it easy to see the alkaline (pH) differences. Now, a little about pH - when you mix an acid and base, they cancel eachother out, neutralizing them. There are many neutral substances though, water and milk, for example. So, what is pH? Really all acidity is is a measurement of Hydrogen ions in a substance. They more hydrogen molecules in a substance the higher the acidity. Any substance added to water that causes an increase in the concentration of hudrogen molecules is considered an Acid. And substance added to water that decreases the concentration is considered a Base. The lase category of substances, as those that help resist changes in pH, these substances are called Buffers. As they help protect the water from changing pH level. Bonus: Now that you know which substances are acids. Think of which one would best remove the grime on an old penny. The substance with the highest acidity level. This is the one that you needed to add less of to turn the cabbage water back to its original color. Drop a penny in an old cup, add a bit of your acid ad watch it work!

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