j0173982(p)[1].gif (12400 bytes) Measuring pH of Direct and Throughfall Rain

A Rising Tide Project for Grades 11 and 12

Methods
Introduction

Classroom Activities
   pH
   Ions

Resources and Links

Glossary

Main l Classroom Activity l Objectives l Standards Addressed l Background l Methods/Teacher Guide l  Rubric l Resources

To the teacher:

            This activity allows the student to apply hands-on acquired data to development of scientific literacy.  Step-by-step instructions are given to lead the student through each step of inquiry as well as complete instructions for proper writing of a laboratory report.  The classroom strategy to be used by the teacher to complete this assignment is as follows:

 1.  Keep in mind the Key Points throughout the facilitation of this activity:   

  • The acidity of the rain falling on the ecosystem is only one component in understanding the chemical interactions that take place between plants and precipitation. 
  • All measurements made from each student group will be used to satisfy ‘repeated trials’ and ‘accuracy of measurement’ requirements in the scientific method.  The pH measurements made for each collection bottle by each group of students will be averaged.  The average pH of direct precipitation will be compared to the average pH of throughfall precipitation as measured by all students. 
  • Most precipitation from the atmosphere is acidic.  Pollution (industrial and natural) causes an increase of acidity in precipitation.   

2.  The detailed information:  in-depth background of terms, conditions, and processes that need to be understood by the student.   Using the Key Terms as listed in Main and Resources will assist students in their research and writing. 

  • pH is a measure of the concentration of hydronium ions in a solution.  It is measured on a scale of 0 to 14.  On this scale, pH 7 is a neutral solution; pH below 7 is acidic; and pH above 7 is basic. 
  • An increased amount in the concentration of hydronium ions, H+, will cause a solution to be acidic. 
  • An increased amount in the concentration of hydroxide ions, OH-, will cause a solution to be basic. 
  • A balanced amount of hydronium and hydroxide ions will be present in a neutral solution. 
  • Pure water has a pH of 7.  Acid rain has a pH lower than 7. 
  • Acids are corrosive, taste sour.
  • Bases are caustic, taste bitter, are slippery. 
  • Precipitation comes in all forms:  rain, sleet, hail, snow, and fog. 
  • Acid rain is a term used for all types of acidic precipitation. 
  • Direct precipitation falls directly to the ground without organic interference. 
  • Throughfall is precipitation that falls through the leaves and branches of trees and bushes. 
  • Deposition is the deposit of any organic or inorganic matter on the leaves or branches of any plant from the atmosphere.  The deposition of insects, bird waste products, or atmospheric compounds may ‘wash off’ into the collection bottles for throughfall precipitation. 
  • Examples of acids and bases:

 Acids      Name                         Formula             Common product 

                        Acetic                             HC2H3O2             vinegar

                        Citric                               H3C6H5               grapefruit

                        Acetasalicylic                  HC9H7O4            aspirin

                        Sulfuric                             H2SO4                 car batteries

                        Hydrochloric                    HCl                       stomach acidstomach acid

                        Phosphoric                      H3PO4                 detergent, soft drinks

 

  Bases           Name                       Formula              Common product 

                        Lime                               CaO                   neutralizer for acidic soil

                        Ammonia                        NH3                   fertilizers

                        Sodium hydroxide           NaOH                oven cleaners, soaps

                        Magnesium hydroxide    Mg(OH)2            milk of magnesia

                        Potassium hydroxide       KOH                  soaps

                        Calcium hydroxide         Ca(OH)2           cement, plaster

 

3.  Give each student a print-out of the classroom activity, key terms (Resources), and rubric (Resources).  Guide them through each step of the activity.  Contact Rebecca Ward at rward@sh.hcs.k12.sc.us if you have any questions or comments.