What is the pH?

Keywords: acid, alkalinity, basic, predictor, acid rain; Lesson Grade Level: 3rd - 5th grade; Total Time Required: 2 - 45 minute periods; Setting: Classroom

Subjects Covered: Science

Topics Covered: pH testing

Goals for the Lesson

Students will learn that different liquids have different pH levels.  They will understand that pH levels have both negative and positive effects on organisms and objects.

Materials Needed

1 tray per group
1 pH Test Kit per group
For each group- the following liquids which are divided into 8 clear cups that have the letters A,B,C,D,E,F,G,H 

vinegar (2.8), soda (3.0), orange juice (3.5), coffee (5.0), milk (6.4), water (7.0), detergent (8-9), milk of magnesia (10.5)

magazines to cut pictures
glue sticks
Per Group – bulletin board paper cut 1 foot wide by 6 foot long. 
        Ahead of the bottom of the paper, write the number 1 at the left side, 7 in the middle, and 14 on the right side.  Add the numbers 2,3,4,5,6,8,9,10,11,12,13 at even intervals.  Leave enough room above the numbers to add pictures of items found in magazines.
State Standards Addressed:
S4.A.1.3 Recognize and describe change in natural or human-made systems and the possible effects of those changes.
S4.A.2.2 Identify appropriate instruments for a specific task and describe the information the instrument can provide.
S4.B.3.2 Describe, explain, and predict change in natural or human-made systems and the possible effects of those changes on the environment.
S4.B.3.3 Identify and describe human reliance on the environment at the individual or the community level.


*Set up six trays ahead of class and have them off to the side.
Explain to students that all liquids have a pH level.  pH (the power of Hydrogen) is an indicator of water acidity or alkalinity.  It ranges from 1 – 14.  Any product with a measure of less than 7 is considered an acid while anything greater than 7 is alkaline or basic.  Products with a measure of 7 are considered neutral.
Remind students that they are performing scientific tests and they are never to drink an unknown substance.
Demonstrate how to conduct a pH test and how to read the results.
Hand out the trays of liquids and let the students conduct the experiments on their cups of liquids.  When all of the tests are completed they should line them up from most acid on the left to most basic on the right.
As a group discuss student findings and write the correct sequence on the board.
Explain that they will be creating a group pH scale using pictures.  Pass out the magazines, scissors, and group paper.  Have students check with their group partners for accuracy before the final gluing on the scale.
•    As a final wrap up conversation with the whole class, explain that many factories in the US burn fossil fuels like coal, oil, and gas which release sulfur dioxide and nitrous oxide into the air.  When these chemicals mix with precipitation like rain and snow they fall as ACID RAIN.  Ask the students how they think acid rain will effect their community.
Ex: The rain falls on the ground and goes into the watershed where it effects the pH in the rivers and streams.  Fish need a pH level of 7to live and anything below that will quickly kill them off.
•    What would happen if a train car carrying baking soda derailed on a rainy night?
Ex: The rainwater would run into the streams and make the water too alkaline for the fish and macro-organisms and they would die.


Teacher observation during the experiment the teacher will visit with groups to make sure students are using correct procedures and reading final strips correctly.  After completing the pH scales students should have at least 15/18 pictures glued in the correct pH level number.  

Literature/Sources Cited

“Trout in the Classroom Activity Guide and Reference for Teachers”


Sandra Speakman, Avon Grove Charter School 4th grade