Water and pH

Read the entire lab before you begin any work. Take time to organize the materials you will need and set aside a safe workspace in which to complete the exercise.

Experiment Summary

Students will have the opportunity to explore some unique characteristics of water, learn about pH, and identify if a liquid contains starch. Through the lab the student will learn how anthocyanins from red cabbage can be extracted and used to prepare homemade pH indicator strips. Each student will demonstrate how water can travel up stems in a plant, investigate the pH of common household materials, and explore where starch can be found.

Objectives

Upon completion of this lab, you should be able to:

• Understand characteristics of water.
• Understand the importance of adhesion and cohesion properties.
• Use anthocyanins to determine pH.
• Understand the basics of acids and bases.
• Quickly test for the presence of starch.

Time Allocation:  6.5 hours (2.5 hours of experimentation and 4 hours of incubation -- this experiment does not have to be completed all at one time)

NOTE: The experiment should be conducted as follows:

• Start Exercise 1, and continue working until the 4-hour incubation stage.
• While Exercise 1 incubates, begin Exercise 2.
• Continue working through Exercise 2 until the 4-hour drying time step begins.
• When the incubation and drying time is complete, return to Exercise 1, then Exercise 2, and finally Exercise 3.

***The experiments do not need to be completed all at once.  You do not need to perform Exercise 2 during the 4 hour incubation of Exercise 1.  Just check the experiment after 4-5 hours.  The same is true for the 4 hour drying time of Exercise 2.  This can dry overnight if necessary.  So the experiments could be run over several days if necessary.

Materials