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

A Rising Tide Project for Grades 11 and 12

Background
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

Key Points 

Key Points will give you the main information you should know to teach the activity.   

  • The acidity of the rain falling on the ecosystem is only one component in understanding the chemical interactions that take place between the plants and the precipitation. 
  • All measurements made from each student group will be used to satisfy ‘repeated trials’ and ‘accuracy of measurement’ which are requirements of 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.  Industrial pollution causes an increase of acidity in precipitation. 

 Detailed Information

Detailed Information gives more in-depth background to increase your own knowledge, in case you want to expand upon the activity or are asked detailed questions by students.   

  • 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. Ex:   lemon juice
  • Bases are caustic, taste bitter, are slippery.  Ex: window cleaner
  • 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 washes off or falls through the leaves and branches of trees and bushes. 
  • Dry 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:

Acids             Name                              Formula             Common product 

                        Acetic                            HC2H3O2             vinegar

                        Citric                                H3C6H5               grapefruit

                        Acetasalicylic               HC9H7O4            aspirin

                        Sulfuric                            H2SO4                  car batteries

                        Hydrochloric                  HCl                       stomach 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