Activity: pH Scale
Materials:
pH paper
Lemon Juice
Vinegar
Coca Cola
Coffee
Tap Water
Milk
Distilled Water
Baking Soda and Water
Liquid Antacid
Lime and Water
Sleeve of one ounce portion cups
Sharpies (10)
Masking tape
Procedure:
1. Divide the kids into small groups.
2. Place a small sample of each liquid in a separate container. Label each container
with the name of the liquid using a sharpie and masking tape.
3. Test the pH of each liquid by dipping a 1 ½” piece of pH paper in the liquid.
Record the number on container. Use a new piece of ph paper for each liquid.
4. Once the testing is complete, ask students to help you order the liquids on the
board. You will need to draw the pH scale and label it 1 to 14 with neutral in the
middle.
5. The answers: Lemon Juice – 2, Vinegar – 2 or 3, Cola Soft Drink – 4, Coffee – 5,
Tap Water – 5, Milk – 6, Distilled Water – 6 or 7, Baking Soda and Water – 7,
Liquid Antacid – 9 or 10, Lime and Water - 12. Some kids may have gotten
different pH readings because they interpreted the colors on the pH scale
differently or because there were variations in the pH paper.
Background:
Explain that the pH scale is a simple way to measure the relative acidity of a substance.
The scale ranges from 0 to 14. A solution with a pH of 1 is very acidic, while one with a
pH of 12 or 13 is very basic, or alkaline. A solution with a pH of 7 is considered neutral.
For example, rainwater, which is normally slightly acidic., averages between 5.0 and 5.6.
The pH scale is logarithmic, which means that there is a tenfold difference between
numbers. A solution that has a pH of 4 is about 10 times more acidic than a solution
with a pH of 5.