Lesson Four Acid Rain Formation by MikeJenny

VIEWS: 7 PAGES: 11

									               Lesson One: Acids/Bases and Acid Rain Formation
            Created for SPICE by Shanna Ratnesar and Sara Charbonnet

Key Questions:
What is an acid?
What is a base?
How do you measure pH?
How is acid rain formed?

Lesson Summary: During this lesson students will:
       Differentiate between an acid and a base
       Measure the pH of several household liquids
       Classify liquids according to pH
       Observe and explain the formation of acid rain (Demo)
       Devise an experiment to test the effects of acid rain on plants and
        animals

Grade Level: 6th-8th

Subjects: Chemistry, Ecosystem Health, Water Cycle, Math, Language Arts

Process Skills Used: Scientific Method, Hypothesizing, Observations,
Measurement, Inferring, Predicting

Time   Estimates:
      Background (10 min)
      Acid-Base Lab (35 min)
      Acid Rain Formation Demo (15 min)

Learning Styles Used: Visual, Kinesthetic, Auditory

Key Vocabulary:
    Acid, Base, pH, Acid Rain, Acidification, Ecosystem, Buffer, pH Paper,
     neutral
Objectives:
   Measure the acidic/basic characteristics of various liquids
   Observe and explain the formation of acid rain
   Develop a procedure for testing the effects of acidity on plants and animals

Materials for Acid-Base Lab:
   Per Lab Group of 4
         o 50 mL of lemon juice (Citric Acid C6H8O7)
         o 50 mL of ammonia (NH3)
         o 50 mL distilled water (H2O(di))
         o 50 mL of tap water (H2O(tap))
         o 50 mL of milk
         o 50 mL of liquid laundry detergent
         o 6 strips of Litmus Paper (pH range of 1.0-12.0)
         o Graduated Cylinder
         o tweezers
         o 6 Beakers
         o Safety Goggles
Materials for Acid Rain Formation Demo:
   Per Class
         o Reaction flask (Erlenmeyer)
         o Stopper for reaction flask that has a hole to fit Teflon tubing outer
            diameter
         o Teflon tubing
         o Small beaker
         o Sodium Nitrite (NaNO2)
         o 10% Sulfuric Acid (H2SO4)
         o pH indicator strips (pH range of 1.0-7.0)
         o Safety goggles
         o (See Figure of Experimental Set-Up Below)


                           Teflon                               Note: Reaction flask
                           Tubing
                                                                should be slightly
                                                                higher than beaker
                                                                w/ water
      Reaction Flask w/
                                                    Beaker w/
      Sulfuric Acid and
                                           100 mL     Water
       Sodium Nitrite
Background Information:
       Acid rain is the wet and dry deposition of acidic substances from the
atmosphere. These substances may be in the form of acid precipitation from rain,
snow, and cloud water droplets or as solid particles which have acidic properties.
Acidity is measured in pH units. The pH of a liquid is a measure of the number of
hydrogen ions present in a solution and is measured on a scale of 0 to 14. Pure
water has a pH of 7 which is referred to as neutral. A liquid that has a pH of less
than 7 is considered an acid, and a liquid that has a pH greater than 7 is
considered a base. Rain water normally has a pH of 5-6 due to the formation of
carbonic acid in the atmosphere when CO2 disassociates into rainwater. During the
early 1970’s acidic rain with pH values of about 2 to 6 were measured in various
parts of the world with average rainfall values ranging from 4-5. This acid rain
formation is due to the transformation of SO2 and NOx into acids when absorbed
into cloud water and raindrops. SO2 and NOx are absorbed into aqueous droplets
and react with water to form acid rain.
       Acid rain formation is due to the emissions of SO2 and NOx during the
combustion of fossil fuels in industrial nations such as Western European countries
and North America. About two thirds of the sulfur oxides in the United States are
emitted from coal fired power plants. Industrial fuel combustion and industrial
processes such as petroleum refining, sulfuric acid manufacturing, and smelting of
nonferrouse metals account for other sources of sulfur dioxide pollution. One of
the largest contributors of NOx is the combustion of gasoline for driving motor
vehicles. These pollutants can remain in the atmosphere and travel hundreds of
kilometers from their source effecting surrounding regions.
       Acid rain is a large concern due its effects on the environment. The
acidification of natural water sources can be detrimental to local ecosystems.
Trout and salmon are sensitive to low pH and reproduction in fish fails to occur at a
pH less than 5.5. Food supply for fish such as plankton and bottom fauna are also
negatively affected by lower pH. Acid rain can also lead to loss of productivity of
crops and forest lands and the increased corrosion of materials such as statues
and objects made of metal.
       Some ecosystems have a natural capacity to neutralize the effects of acid
rain. In areas where the geology of the bedrock is limestone, a basic substance,
acidification can be neutralized due to reactions between the basic limestone and
acidic rain.
The control of SO2 and NOx at the source is the long-term solution to acid rain
problems. There are two approaches to the control of SOX emissions.
Desulphurization of fossil fuels can help reduce the production of acid rain forming
pollutants in the atmosphere during combustion. The second option for prevention
of pollution is the removal of SO2 gases from exhaust. In limestone scrubbing
limestone slurry is used to neutralize the sulfur dioxide gas being produced in
exhaust. The sulfur dioxide is converted to calcium sulphate in the following
reaction:

               CaCO3(s) + H2O + 2SO2-> Ca+2 + 2HSO3- + CO2(g)
                CaCO3(s) + 2HSO3-+ Ca+2 > 2CaSO3+ CO2 + H20
NOx is removed from the exhaust of vehicle emissions using catalytic converters.

       The United States is the largest consumer of energy derived from fossil
fuels, about 35%, yet the US contains only 6% of the current world population. By
understanding our role in the world economy and the strain put forth by large
resource consumers such as the United States and Western European countries we
can work towards attaining a more sustainable, cleaner environment.
       Students can help to reduce the effects of acid rain by using less electricity
in their home and classroom by tuurning off lights, TV’s, computers, conserving
water, and using less paper. Also the use of renewable non-polluting sources of
energy such as solar and wind power are becoming more popular. These new
technologies will help reduce the combustion of fossil fuels for power and help
prevent pollution and the effects of acid rain on the environment.

References:
    Wark, Kenneth; Warner, Cecil; Davis, Wayne. Air Pollution Its Origin and
      Control. 3rd Edition. Addison Wesley. 1998
    Air and Waste Management Association. Environmental Resource Guide 6th-
      8th Air Quality. 1991
    Cooper, David; Alley, F. Air Pollution Control: A Design Approach. 3rd
      Edition. Waveland Press, Inc. 2002
    The Economist. Pocket World in Figures: 2002 Edition. Profile Books Ltd.
      2002
    Marland, G.; Boden, T.; Andres, R. Online Trends: A Compendium of Data on
      Global Change. http://cdiac.
esd.ornl.gov/trends/emis.em_cont.htm. June 3rd
Preparation for Acid Base Lab:
    Set out 6 beakers per lab group, 1 graduated cylinder, goggles, litmus strips,
      and liquids to be tested
    Have students measure out 50 mL of each liquids (can be used to reinforce
      measurement skills)

Preparation for Acid Rain Formation Demo:
    Set up experimental set-up as shown above, do not add chemicals yet
    WARNING: This experiment needs to be performed in a well ventilated
      area (if possible outside), with a fume hood or exhaust fan, students should
      be at least ten feet away
    The reaction flask needs to be slightly elevated above the beaker, a stand
      with a clamp and rod may be used
    The hole in the stopper for the reaction flask needs to fit snugly around the
      Teflon tubing used to transfer the gas over to the open beaker, vacuum
      grease may be used to create an airtight seal
    Remember to use safety goggles when using chemicals.

Procedure for Acid/Base Lab:

   1. Label one beaker with permanent marker for each of the following liquids:
      lemon juice, ammonia, deionized water, tap water, milk, laundry detergent (2
      min).
   2. Using a graduated cylinder, measure out 50 mL of the of each liquid into the
      beakers (10 min)
   3. Using tweezers dip one end a pH litmus test strip into the beaker containing
      lemon juice. Remove the strip and observe the color. Compare the color to
      the color wheel of the pH range. Determine the pH of the liquid. Record
      the pH (2 min)
   4. Rinse.
   5. Repeat step 3 and 4 for each liquid (8 min).
                   (See attached worksheet for data tables)
Procedure for Acid Rain Demo:

   1. Set-Up the experimental set-up as shown above (1 hr).
   2. Pour 100 mL of room temperature distilled water into a beaker. Measure
      the pH of the distilled water using a strip of litmus pH indicator strip. Show
      the students in the classroom the strip and ask them to check against their
      color wheel. Have the students detect the pH. Record pH (4 min).
   3. Pour 5 grams of sodium nitrite into the reaction flask (1 min).
   4. Have stopper and test tube configuration ready for placement into the
      reaction flask
   5. Pour 50 mL of 10 % Sulfuric acid into the reaction flask. Immediately cap
      the reaction flask with the stopper/Teflon tube piping system (1 min)
   6. Observe what is occurring. HONO (nitrous acid) gas is formed due to
      reaction between the sulfuric acid and sodium nitrite. Ask students to
      describe the appearance of the gas? Color? Odor? Where is it going? (It
      should begin to bubble through the water). What do they think is happening
      in the beaker with the water? (5 min)
   7. Allow the reaction to continue until completion; continue to shake until all
      sodium nitrite is consumed, continue until no more gas is being produced in
      the reaction flask and all the gas has bubbled through the deionized water
      (10 min).
   8. Using tweezers, dip one of the litmus paper into the deionized water which
      has now been converted to sulfuric acid. Ask students to compare the litmus
      paper strip to the pH color wheel. Have the students detect the pH.
      Record new pH of solution in beaker. The pH should be lowered to about 1-3
      (5 min).

Assessment Suggestions:
    Students design an experiment to determine the effects of acid rain on
      plants, (see corresponding Worksheet for Lesson # 1 and Lesson 2 for
      ideas) including problem, hypothesis, procedure, materials needed
    Students answer questions located on the backside of lab worksheet (see
      corresponding Worksheet for Lesson # 1)
Extensions:

     See attached power point presentation “AcidRain.ppt” for use in presenting
      introduction and discussion
     After learning about acid rain formation, have student perform research on-
      line about local ecosystems impacted by acid rain, check local water
      management districts and Department of Environmental protection
     For more information check the following websites
          o EPA Kids Website
                 http://www.epa.gov/kids/air.htm
          o EPA Acid Rain Website
                 http://www.epa.gov/airmarkets/arp
          o Department of Energy
                 http://www.energy.gov/engine/content.do?BT_CODE=EN_SS1
          o USGS On-Line Data for Acid Rain
                 http://bqs.usgs.gov/acidrain/

References:
    Air and Waste Management Association. Environmental Resource Guide 6th-
     8th Air Quality. 1991
Provided by


Group:___________________________
Period:_________
                    Lesson # 1 Student Worksheet
                         Acids and Bases Lab

Objectives:
  1. Measure acidic/basic characteristics of various liquids.
  2. Develop a procedure for testing the affects of acidity on plants and animals.

Background:
     Acidity is measured in pH units. pH is measured on a scale of 0 to 14, where
     7 is considered neutral. A pH value below 7 indicates acidity, and a pH value
     above 7 indicates basicity also known as alkalinity. Litmus paper is used to
     measure pH. In this lab you will be using Litmus paper to determine the pH
     of several household liquids.

Materials:
   50 mL of lemon juice (C6H8O7)
   50 mL of ammonia (NH3),
   50 mL of distilled water (H2O (DI))
   50 mL of tap water (H2O)
   50 mL of milk
   50 mL of laundry detergent
   6 strips of Litmus paper and Color Chart
   Safety Goggles
   6 beakers
   Graduate cylinder
   Tweezers

Procedure:
    Label one beaker with permanent marker for each of the following liquids:
      lemon juice, ammonia, deionized water, tap water, milk, laundry detergent.
    Using a graduated cylinder, measure out 50 mL of each liquid into the
      beakers.
       Using tweezers dip one end a pH litmus test strip into the beaker containing
        lemon juice. Remove the strip and observe the color. Compare the color to
        the color wheel of the pH range. Determine the pH of the liquid. Record
        the pH in Table 1. Dispose of the litmus strips.
       Rinse.
       Repeat step 3 for ammonia, deionized water, tap water, milk, laundry
        detergent.



Data:
                             Table 1: pH of Household Liquids
           Liquid                   Color of Litmus Paper             pH
Lemon juice
Ammonia
Distilled Water
Tap Water
Milk



Analysis:
      1. In the table below record which liquids were acids and which were bases.

                    Liquid                                Acid/Base???
Lemon juice
Ammonia
Distilled Water
Tap Water
Milk

Question:
     1. In some areas, rainfall has been found to be as acidic as lemon juice; do
         you think that plants could grow with such an acidic water source?
                    Acid Rain Formation and Deposition Demo
Objective:
     1. Observe the effect of sulfur dioxide on the acidity (pH) of water.

Background:
     Sulfur dioxide (SO2) and nitrogen dioxide (NO2) are produced from coal-
     burning power plants and motor vehicle emissions. These pollutants react
     with sunlight and water vapor in the atmosphere to form acidic chemicals.
     This demo will simulate what happens when these chemicals deposit into
     lakes and streams or other water bodies. Sulfur dioxide (SO 2) in this
     experiment will be generated by combining liquid sulfuric acid (H2SO4) and
     sodium nitrite (NaNO2).

Observations:
   pH of water in beaker before the reaction:_________________________
   What happens when the sulfuric acid is added to the sodium nitrate?




      pH of water in beaker after the reaction:__________________________
      How do you think this change would affect plants and animals?




      Devise an experiment that can be done to test how acidity affects plants
       and animals:




      Devise an experiment to test the pH of the rainfall in our area:

								
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