Ph
Testing
OBJECTIVES
1.
The student will understand what PH is.
2.
The students will measure PH levels of various liquids
using a PH kit.
BACKGROUND
The PH scale was
devised by a Danish bio chem., Soren Sorensen, in 1909.
The PH is the value of a solution’s acidity or basicity
(or alkalinity). The
initials PH represent two French words pouvoir hydrogene, which
means “hydrogen power. The
PH scale’s values range from 0-14.
Acidic solutions have PH values below 7, with the most
acidic solutions having a PH value near 0.
Basic or alkaline, solutions have PH values above 7, with
the most basic solutions having a PH close to 14.
The PH of a neutral solution – a solution that is
neither acidic or basic is 7.
To test the PH of vinegar students will use the PH test
kit.
Materials:
§
PH test kit or PH test paper
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3 plastic cups
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water
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baking soda
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lemon juice
§
vinegar
§
ammonia
PROCEDURE
1.
Discuss
with class that all chemicals can be divided into 3 categories:
acid, base or neutral.
2.
Ask
students if they’ve ever tasted salad dressing or lemonade.
3.
Discuss
with class that these are examples of acids.
They have a sour taste.
4.
Share
with students that the opposite of an acid is a base. Some common bases are baking soda, bleach and milk of
magnesia (for acid indigestion).
5.
Test
the various samples one at a time and record results. (You may want to exclude the pictures on the chart until
after this testing time to help the students discover the
results on their own.
6.
Share
results as a class. Encourage
students to guess and check what the PH is of each solution.
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Solution
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My PH Prediction
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Actual Reading or Level
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7.
Discuss
results as a class. How
many of you made a close prediction?
ASSESSMENT
§
Quiz about PH
§
Have class fill in chart/or make their own PH
chart. Test some
more solutions using the PH kit.
EXTENSION
§
Follow up w/ cabbage experiment
§
test solutions at home with an adult
§
test your pool water at home with an adult
§
discuss why the PH level in a pool needs to be a
certain level
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