Mystery Science: Part IV: How to Complete Ph Testing
In this test, students are testing the pH of a substance in an effort to determine more about how the crime may have occurred. Measuring this aspect of a substance and learning how pH affects the behavior of a substance and its relation to other chemicals is an important component of chemistry. In our mystery, soda is an acid because of the ingredient phosphoric acid and sleeping potion (for the purposes of this mystery) is a base.
You can make pH testing material by either:
2) You can make a solution to test pH out of red cabbage. Click here for a full explanation of how to make a red cabbage acid/base indicator. Test strips can also be made from the red cabbage the same way they are made for the turmeric - dip paper towels in the red cabbage juice and then hang to dry.
3) You can buy red and blue test strips which are called "litmus paper."
Before you begin the experimenting with your students, you will need to pour about 1/4 cup of soda in the glass you will be using to be from the crime scene. You will need to use the same glass next week when we get fingerprints, so you should use a glass made of glass, not plastic. Add about 1/2 teaspoon of baking soda to the soda.
If the cola contained a sleeping potion, who does this indicate might be involved in the kidnapping?
You can make pH testing material by either:
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| 1) Test strips can be made from the spice turmeric. To make some pH strips this put 1/4 cup alcohol in a bowl and stir in 1/4 tsp of turmeric. |
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| Dip coffee filters in the solution until completely covered and yellow. Hang up or place on a cookie sheet to dry. Move them occasionally as they dry to prevent them from sticking. Once dry, cut them into strips. Now they can be used to test acids and bases. |
3) You can buy red and blue test strips which are called "litmus paper."
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| If you would like to see our experimenting, click here. |
You should begin by using the test strips to test a known acid and a known base to have something to compare the testing to. Then test the contents of the mystery glass. If you wish you can have them test other household items while you have the indicator strips all out and ready to use.
Who do you think would have access to and knowledge of the sleeping potion?
Check the names off on your worksheet.
You can also make a guess in the poll. You can always change your guess.
Sources:
GEMS: Of Cabbages and Chemistry
Grades 4-8
4 Sessions
88 pages
Students explore acids and bases using the special indicator properties of red cabbage juice. The color-change game Presto Change-O helps students discover the acid-neutral-base continuum. They learn that chemicals can be grouped by behaviors, and relate acids and bases to their own daily experience. An “Acid and Aliens from Outer Space” extension activity can be presented to reinforce student learning or as an assessment. The unit is an excellent lead-in to the GEMS guide Acid Rain.
