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
§
3 plastic cups
§
water
§
baking soda
§
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.
|
Solution
|
My PH Prediction
|
Actual Reading or Level
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
|
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
|
