The Dynamic Duo Share Ideas on How to Teach Chemistry

Eva Lou Apel &

Barbara Schumann

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The Dynamic Duo

The Dynamic Duo Shares Ideas on How to Teach Chemistry Eva Lou Apel and Barbara Schumann

First Edition November 2007 Austin, Texas

© 2007 Eva Lou Apel & Barbara Schumann

This work is licensed under a Creative Commons License—Attribution. You may copy, distribute, display, and use this copyrighted work — and derivative works based upon it — but only if you give credit to The Dynamic Duo Shares ideas on How to Teach Chemistry, First Edition, Eva Lou Apel & Barbara

Schumann.

Chemical Education Consultant Barbara J. Schumann 1405 Thaddeus Cove

Austin, Texas 78746-6321 512-327-5449

Fax: 512-327-6207 E-mail: bjschumann@msn.com

Chemical Education Consultant

Eva Lou Apel 2506 Plantation Creek Court Missouri City, TX 77459-291

281-499-2708 E-mail: eapel2@aol.com

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The Dynamic Duo

Foreword

Eva Lou and Barbara taught together at Westlake High School in Austin from 1982 – 1993. They team taught chemistry. They developed many labs and teaching ideas. They gave many workshops together. They continue to give workshops together. In their early years of teaching together Eva Lou and Barbara started a demo club. They had a student named Robbie. He was a member of the demo club. Barbara taught him one semester and Eva Lou the other. He named them the “Dynamic Duo”. He gave them Tee shirts for Christmas with the “Dynamic Duo” lettering on them. The name stuck. They still have those shirts. Eva Lou Apel BS Chemistry-Texas Woman’s University. Graduate work --- Texas A&M University, Hope College, University of California at Berkeley and the University of Arizona. Eva Lou has taught physical science, chemistry and AP chemistry for 26 years in the Waco, Texas Public Schools, Houston, Texas Public Schools, and at Westlake High in Austin, Texas before retiring in 1993. She also has worked in the analytical chemistry lab for Shell Development Company’s Research Lab in Houston. For the past seven years she has worked as an Independent Representative for George Seidel and Associates rep-resenting Flinn Scientific. Eva Lou has attended many NSF summer institutes including the AP Chemistry Workshop at Hope College, the Woodrow Wilson Chemistry Institute at Princeton in 1986, the ICE Institute at Berkeley, and the ICE Institute at the University of Arizona. She received the Texas Excellence Award for Outstanding High School Teachers from the University of Texas in 1987, the Outstanding Chemistry Teacher Award from the Central Texas Section of the ACS in 1988 and was named as a Life Time Honorary Member of the Texas Chem-istry Teachers organization in 1994. She has presented over seventy-five workshops at the local, state and national levels. Barbara J. Schumann BS chemistry – University of Texas at Austin. Graduate Work – University of New York at New Paltz, University of California at Berkeley, and the University of Michigan at Ann Ar-bor. Barbara taught algebra, physical science and chemistry for 20 years in the Houston, Austin and Eanes Public School Systems and in Wappingers Falls Central School District in New York. She substituted for 12 years in New York. She attended many NSF summer institutes including the Woodrow Wilson Institute at Princeton in 1989, the ICE Institute at Berkeley, the ICE Institute at the University of Michi-gan at Ann Arbor, Frontiers in Science at Tufts University, and was trained in Teaching Science with Toys at the University of Ohio at Miami of Ohio. She was trained by the American Chemical Society in Operation Chemistry at the University of Wisconsin and Purdue University. She was a member of the Central Texas Operation Chemistry team for several years.

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The Dynamic Duo

Foreword She was selected by the Central Texas Region of the American Chemical Society as the Chemistry Teacher of the year in Travis County in 1989, nominated for the Presidential Award in Teaching in 1989, selected at the Chemistry Teacher of the year in the state of Texas by the Associated Chemistry Teachers of the State of Texas in 1997 and received the Spirit of Education Award at Westlake High School in 1998. She was awarded an honorary membership in the Associated Chemistry Teachers of the State of Texas. She has served for several years as the historian of that organization. Since 1998 she has worked as an independent representative for George Seidel and As-sociates representing Flinn Scientific. She has presented over 100 workshops.

Eva Lou Barbara

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The Dynamic Duo

Rainbow Tube

Background: This activity can be used to introduce the concept of pH indicators. Vinegar is a dilute so-lution of acetic acid (HC2H3O2). Sodium Carbonate (washing soda) has a pH greater than 7. The indicator used is a universal indicator. It is which is a mixture of indicators and has a distinctive color at each pH. The sodium carbonate is more dense than the vinegar. It sinks and neutralizes the vinegar as it moves down the column. The indicator in the vinegar indicates how the pH is changing. Materials: Clear plastic straw glued at one end with hot glue gun, dilute vinegar + indicator solution, sodium carbonate (washing soda solution), 96-well plate Safety: Wear Goggles. Sodium carbonate has a pH greater than 7. Keep away from eyes and skin. Tube can be discarded in regular trash after a few days. Directions: 1. Write initials on prepared straw (glued shut on one end) with permanent pen. Set upright in 96-well plate. 2. Fill the straw nearly full of the vinegar-indicator solution with thin-stem Beral Pi-pette. Vinegar is dilute acetic acid (HC2H3O2). 3. Deliver the solution down the side of the straw so that no air bubbles form. Add 2 to 3 drops of the Na2CO3 solution to the straw with thin-stem Beral pipette. Wait 10 to 15 seconds for this dense solution to sink, then add 2 to 3 drops more. Then add 3 more drops. Na2CO3 has a pH > 7. It is more dense than the vinegar solution, so it sinks to the bottom of the tube. 5. Hold the straw vertically to watch the colors. 6. The indicator used is a mixture of many indicators. The color change is indicated as follows: We will use Yamada's Universal Indicator It exhibits the ROY G BIV color sequence in the pH range 4-10 Color: red orange yellow green blue indigo violet pH: 4 5 6 7 8 9 10 7. Have the teacher glue the other end. Store upright and observe over a week.

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The Dynamic Duo

Rainbow Tube

Questions: 1. Describe what you see. 2. What caused this reaction? 3. After the prepared straw sits for awhile, how does it look? Directions for Teacher Materials: 1. Transparent plastic straws – Sam’s is a good source. Glue at one end with hot glue gun. Let it sit for a few days. 2. A saturated solution of Na2CO3 (washing soda). WARNING: THIS IS A STRONG BASE. 3. A dilute vinegar solution - 100 ml per liter of distilled water. 4. Prepare the vinegar-indicator solution by adding 50ml indicator to 250ml of pre-pared vinegar solution. 5. You may purchase universal indicator or prepare Yamada indicator. To prepare 200 ml Yamada Indicator: Dissolve 0.005 g thymol blue, 0.012g methyl red, 0.060g bromthymol blue, and 0.10g phe-nolphthalein in 100 ml ethyl alcohol. Add 0.01M sodium hydroxide until the solution is green and dilute to 200 ml with distilled water.

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The Dynamic Duo

Electroplating Copper

Materials: 1 film canister 3 slits in top 1 plastic strip 2 cm by 7 cm. 1 copper strip 1.5 cm by 6 cm. copper plating solution 9 volt battery 1 red and 1 black connectors, insulated wire with small alligator clips at each end 1 iron nail or other metal object Buret clamp ring stand Acetone (optional) Copper Plating Solution: 200g of CuSO4. 5H2O, 17.2 ml of conc. H2SO4, 8.25 ml of 0.1M HCI. Dilute to 1 liter. Safety: Wear safety goggles and aprons. The plating solution is very acidic. Neutralize with bak-ing soda if spilled. Stabilize the film canister by using Buret clamp to attach to ring stand. Use acetone to clean nail in well -ventilated area, under hood if possible. Reuse acetone. Procedure: 1. Clean object to be plated with acetone under the hood. This can be a nail or another

metal object. 2. Assemble lid of cell. Plastic strip is in middle and copper strip to one side and nail or

object in the other. 3. Attach bottom of film canister to ring stand with Buret clamp. 4. Fill canister 3/4 full of copper sulfate solution and tightly seal with assembled lid. 5. Connect battery to cell with leads. Connect the object to be plated to the positive terminal of the battery and the copper strip to the positive terminal of the battery. 6. Wait 1 minute. Carefully disconnect battery and remove lid of cell. Observe object (nail) plated. Record Observations: Remove plated object. Rinse lid with distilled water in water bottle. Pour back copper plating solution into original container for recycling.

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The Dynamic Duo

Testing Antacid Tablets

Introduction Recently there have been numerous advertisements for antacids on television. These products are used to neutralize stomach acids. How do these antacids work? Most ant-acids usually contain carbonates, bicarbonates, or hydroxides. All act as bases and have a neutralizing effect on acids. The carbonates and bicarbonates also produce CO2 when they react with acids. This buildup of gas in the stomach causes the expulsion of the gas, the burp. This also provides relief. Many antacids contain calcium compounds are not very soluble in water. This increases the possibility of an antacid being absorbed into the bloodstream. If too much base is absorbed into the bloodstream a condition called alkalo-sis occurs. In this experiment, you will use HCl to neutralize the antacids. You will determine which antacid is most effective in neutralizing the acid. Real stomach acid is HCl with a pH range of 0.9 to 1.5. We will use 1.0 M HCl in this lab. The process of gradually adding an acid to a base or a base to an acid until neutralization occurs is called titration. The number of milliliters it takes to neutralize the acid or base is carefully measured. An indicator is used to show the endpoint, the point at which neutrali-zation occurs. Indicators are organic compounds, which may be different colors at a dif-ferent pH. The colors at a different pH vary according to the indicator. It is important that the color change in the indicator can be detected when the pH is changed. Crystal Violet has been chosen for this titration. Below pH 0.8 it is yellow. Between pH 0.8 and pH 1.1 it is green. Above pH of 1.1 it is blue. Since the pH range of the stomach is 0.9 to 1.5, this is a good indicator to use. What you are trying to do with the antacids is to get the pH of the stomach back to a normal pH range of 0.9 to 1.5. In this lab, the more milliliters of HCl it takes to neutralize the antacid, the more effective the antacid is in neutralizing the acid in the stomach. In a standard neutralization an acid + base → salt + water Example: NaOH + HCl → NaCl + HOH Carbonates + bicarbonates + acid → a salt + carbon dioxide + water This is also a type of neutralization. NaHCO3 + HCl → NaCl + H2CO3 ↓ H2O + CO2 Materials: 1.0 M HCl, water bottle filled with distilled water, 0.04 gram samples powdered antacids, 1 ml syringe, microstopcock (Flinn # AP9159), microtip Beral-type pipet, scissors, condiment cup for waste, 50 ml Erlenmeyer flask, crystal violet indicator in pipet, stirring rod, weigh-

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The Dynamic Duo

Testing Antacid Tablets

ing dish, balance accurate to .01or .001 gram, ring stand, clothespin holders or 96 well plate and microchem support stand (Flinn # AP9013) . Safety: Wear goggles at all times. HCl is corrosive. If spilled, neutralize with baking soda. Procedure 1. Mass 0.04 gram sample of powdered antacid in weighing dish or 1 oz condiment cup. 2. Transfer dry powder to a 50 ml Erlenmeyer flask or leave in condiment cup 3. Add a few ml of water from water bottle to rinse the weighing dish and add this to the

Erlenmeyer flask. Repeat rinsing a second time. All of the solid may not dissolve. The antacid contains some “fillers” that may be insoluble. All of the active ingredients will dissolve as HCl is added.

4. Add 3 drops of crystal violet indicator. Note the color. This is a basic solution. 5. Cut off the tip and the top of the microtip Beral-type pipet to form a funnel. 6. Put tip of microtip Beral-type pipet on the end of the microstopcock and attach the

stopcock to the bottom of the syringe. 7. Remove the plunger from the syringe and put the funnel you formed from the microtip

pipet on top of syringe. 8. Steps 5 ,6,and 7 may have been done for you. Attach the syringe to ring stand with the

clothespin holder. 9. Close stopcock. Place waste condiment cup underneath syringe. 10. Fill the red dot syringe buret with 1M HCl with a thin-stem pipette. Check to see that

there are no bubbles. Allow some of the solution to drain into the waste container to fill the stopcock and the tip with solution. Refill the syringe buret until the HCl level is at or just below the 1.00ml mark. Record the initial reading of HCl .

11. Place the Erlenmeyer flask or condiment cup with the antacid and indicator beneath tip of stopcock. Open stopcock so that one drop of acid comes out at a time. Gently swirl Erlenmeyer flask. Add HCl until the color remains a definite blue with a tinge of green. Immediately close stopcock and take reading. Record as final reading of acid.

12. Empty contents of Erlenmeyer flask into waste container. Rinse several times with distilled water until clean.

13. Repeat procedure with another antacid.

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Testing Antacid Tablets

Report Page Data Table

Questions: What was the color of the indicator in the basic solution? __________________________ What was the color of the indicator at neutralization?______________________________ Which antacid was the best acid neutralizer and why? ____________________________ ______________________________________________________________________________________________________________________________________________ What was the main ingredient of Tums? _______________________________________ Write and equation of the reaction of Tums with HCl.

Trial #1(Name) #2(Name) #3(Name)

Initial volume of acid

ml

ml

ml

Final volume of acid

ml

ml

ml

Volume of acid reacted

ml

ml

ml

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The Dynamic Duo

Vitamin C Content of Fruit Juices

Introduction Vitamin C, ascorbic acid, is produced naturally by plants and animals except for humans. A deficiency in Vitamin C causes a disease known as scurvy, the symptoms of which are bleeding, spongy gums and a tendency to bruise easily. Because our body has a limited ability to store Vitamin C, it is necessary to eat foods, which contain Vitamin C as part of our daily diet. Foods that contain significant amounts of Vitamin C include citrus fruits and some green plants such as spinach and green peppers. The recommended Dietary Al-lowance of vitamin C is 60 mg per day.

Fruit juices naturally contain other acids such as citric acid in addition to ascorbic acid; therefore, an acid-base titration cannot be used to determine the amount of ascorbic acid, Vitamin C. In this lab you will determine the amount of Vitamin C (ascorbic acid) in 1 serving (6 oz) of orange juice, apple juice or other Vitamin C containing juices by titration of the ascorbic acid in the juice with an iodine solution. The chemical reaction involved is the oxidation of ascorbic acid by iodine to dehydroascorbic acid. The end point of the ti-tration will be determined by the formation of the starch-iodine blue-black complex when an excess of iodine becomes present. As long as ascorbic acid is present, the iodine is converted to the colorless iodide ion. Once the ascorbic acid has all reacted, the iodine forms the blue-black complex with the starch indicator. C6H8O6 + I2 → 2 H+ + 2I- + C6H6O6 Vitamin C Oxidized form of vitamin C (Ascorbic acid) (Dehydroascorbic acid) The micro-scale titration will be done using 1 ml syringes as burets. The concentration of the iodine solution will be determined by titrating a standard solution of ascorbic acid, which contains 1 mg ascorbic acid per ml of solution. From this titration’s data, you will calculate the mg Vitamin C equivalent to one ml of the iodine solution. Calculations are simplified because iodine and ascorbic acid react in a 1:1 mole ratio. If 0.72 ml iodine were used to titrate 0.85 ml Vitamin C then: (equation 1)

= 1.2 mg Vitamin C/ml I2 solution

This iodine solution will then be used to titrate the fruit juice. If 0. 50 ml of iodine solution was used to titrate 0.81 ml of orange juice (OJ), the mg Vitamin C per 6 oz. serving of juice will be calculated using the information that 1 oz equals 30 ml. (equation 2)

= 122 mg Vitamin C per serving

1 mg Vitamin C 0.85 ml Vitamin C used

1 ml Vitamin C solution 0.72 ml Iodine solution used

1.2 mg Vit C 0.50 ml I2 30 ml OJ 6 oz

1 ml I2 0.81 ml OJ 1 oz OJ 1 serving

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The Dynamic Duo

Vitamin C Content of Fruit Juices

Materials (Per Lab Group): 1 ml Syringes Standard ascorbic acid solution (1mg/ml) “Poor Man’s” buret micro stopcock Iodine solution 1 microtip Beral-type pipet Starch solution thin stem Beral-type pipets Fruit Juices: orange, apple, lemon, white, grape microchem support stand or ring stand 96 well Reaction Plate 1 25 ml Erlenmeyer Flask waste container or condiment cup Safety Precautions: Goggles and aprons must be worn. The iodine solution may stain hands or clothing and can irritate skin. Ascorbic acid is not considered hazardous, however, students should wash their hands thoroughly after handling. Food items, once brought into a lab, are con-sidered chemicals and, as such, should not be ingested.

Disposal: The small amounts of the solutions may be disposed of down the drain. Any left over io-dine solution should be saved for use in future labs. Procedure 1. Fill the green dot syringe with the standard ascorbic solution. Set the waste container

under the syringe and dispense the solution into the waste container until the liquid level is on or just below the 1.00 mark. Read the volume of ascorbic acid solution and record it in the data table as the initial volume of ascorbic acid.

2. Place the 25 ml flask under the ascorbic acid syringe. Allow about 0.70-0.80 ml of the solution to flow into the flask. Read the level of the solution in the syringe and record as the final volume of ascorbic acid.

3. Place the microchem support in a corner well of the 96 well reaction plate. Place the syringe buret (purple dot) in the support. Another option, attach clothespin microchem support to normal ringstand. Refer to photographs in handout.

4. Place the syringe buret (purple dot) in the microchem support. Fill the syringe with the iodine solution using a thin-stem pipet. Check to see that there are no bubbles. Al-low some of the solution to drain into the waste container to fill the stopcock and tip with the solution. Refill the syringe with iodine so the level is on or just below the 1.00 mark. Read the volume of iodine and record in the data table as the initial volume of iodine.

5. Add 2 drops of starch to the ascorbic acid in the flask. Swirl to mix. 6. Place the flask under the iodine (purple dot) syringe buret. Add iodine drop by drop

with swirling to mix until the solution turns blue-black and remains blue-black after mix-ing. Read the level of the solution to the nearest 0.01 ml and record as the final vol-ume of iodine.

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The Dynamic Duo

Vitamin C Content of Fruit Juices

7. Empty the flask and rinse several times with distilled water. 8. Refill the syringes and repeat procedures # 2-7 for two more trials. 9. Fill the pink dot syringe with distilled water and allow it to flow out into the waste con-

tainer several times. Then fill the syringe with the juice to be tested and allow the juice to flow into the waste container.

10. Fill the syringe with the juice. Set the waste container under the tip and allow enough juice to flow through so the level is on or just below the 1.00 ml mark. Read the vol-ume of the juice and record in the data table as the initial volume of juice.

11. Place the 25ml flask under the juice syringe. Allow about 1.0 ml of the solution to flow into the flask. Read the level of the solution in the syringe and record as the final vol-ume of juice.

12. Add 2 drops of starch and a few ml of distilled water to the juice in the flask. Swirl to mix.

13. Place the flask under the iodine buret. Add iodine drop by drop with swirling to mix until the solution turns blue-black and remains blue-black after mixing. Read the level of the solution to the nearest 0.01 ml and record as the final volume of iodine.

14. Refill the syringes, empty, rinse the flask, and repeat procedures # 12-14 for two more trials.

15. Empty the juice syringe into the waste container. Fill the syringe with distilled water and allow it to flow out into the waste container several times. Then fill the syringe with the another juice to be tested and allow the juice to flow into the waste container.

16. Repeat the titration as above with other juices. The standardization steps do not need to be repeated as long as you are using the same syringe buret.

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The Dynamic Duo

Vitamin C Content of Fruit Juices

Report Page

Data Table Standardization of Iodine

Calculations: 1. Calculate the mg Vitamin C equivalent to 1 ml of the Iodine solution. (See equation 1.)

Show work below for each trial and place your answer in the data table above. Calcu-late the average for the 3 trials and place your answer in the data table above.

TRIAL # 1 2 3

Initial volume Ascorbic acid ml ml ml

Final volume Ascorbic acid ml ml ml

Volume ascorbic Acid used ml ml ml

Initial volume Iodine solution ml ml ml

Final volume Iodine solution ml ml ml

Volume iodine Solution used ml ml ml mg Vitamin C equivalent to 1 ml I2 Average mg Vitamin C equivalent to 1 ml I2 mg

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The Dynamic Duo

Vitamin C Content of Fruit Juices

Fruit Juice Data Table

Calculations & Questions Continued: 2. Calculate the mg of Vitamin C found in a 6 oz. Serving of each juice. (See equation # 2) Show

work below and place your answers in the data table above. 3. Which juice contains the most Vitamin C per serving? ___________________________ 4. Was this your expected result?______ Explain why this might be true. (Hint: Read the label on

the juice container.)

Kind Of Juice Orange Juice Apple Juice Lemon Juice Initial volume Juice ml ml ml Final volume Juice ml ml ml ml juice used ml ml ml initial volume iodine ml ml ml Final volume Iodine ml ml ml ml iodine used ml ml ml mg Vitamin C per 6 oz serving mg mg mg

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The Dynamic Duo

Vitamin C Content of Fruit Juices

Preparation Of Solutions: Standard ascorbic acid solution: Dissolve 0.10 grams of ascorbic acid in enough dis-tilled water to make 100 ml of solution. This solution should be made fresh each day. An alternative method is to make the ascorbic acid by crushing a 100 mg Vitamin C tablet and adding enough water to make 100 ml of solution. One ml of these solutions will con-tain one milligram of ascorbic acid. Iodine solution: Fill a 250 ml volumetric flask about ½ full with distilled water. Dissolve 0.10 g potassium chlorate and 10.00 g of potassium iodide in this water. Add 25 ml 1M sulfuric acid. Swirl to mix. Then add 0.10 g of iodine crystals and dissolve. Add enough distilled water to make 250 ml of solution. The iodine is slow to dissolve. Don’t plan to make it at the last minute. Starch solution: Place about 100 ml of distilled water in a beaker. Generously spray with spray starch (from the grocery store) for a minute or so. Stir and allow foam to dis-perse. The solution should be translucent or milky looking. If necessary spray a second time. (An alternative is to boil water, make a paste of powered starch and cold water and stir the paste into the boiling water.) Teaching Tips: 1. Remove the plunger from the syringe. Fit the stopcock on the bottom of the syringe.

Cut the tip from a microtip pipet about 0.5 cm above the tapered end and fit the tip on the end of the stopcock.

2. The amounts of Vitamin C in different kinds of juice may prove to be the same be-cause of the addition of ascorbic acid as an ingredient. Read the labels and chose those which do not have added Vitamin C.

3. The orange juice used should be low pulp or strained so that the pulp does not clog the stopcock. Baby food juices provide a convenient source of no pulp juice: however most have added ascorbic acid causing the various juices to have approximately the same amount of Vitamin C.

4. Juices other than apple, orange, or lemon can be used in this experiment provided they are light in color. Using darker colored juices, such as grape juice, will make it difficult to determine the end point of the titration.

5. The Vitamin C content of foods decreases if stored uncovered at room temperature or higher temperatures. Vegetables cooked in water lose much of their Vitamin C con-tent.

6. An extension of this experiment could study and graph the decline in Vitamin C con-centration left open in the classroom for a period of days.

7. Another extension could compare the Vitamin C content in canned, frozen, bottled and fresh squeezed orange juice.

8. The cost of Vitamin C from different sources could be studied. Adapted from a lab by Bro. Carmen V. Ciardullo in Microaction Chemistry V 2 published by Flinn Scientific Inc

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Boyle’s Law Purpose: In this lab you will measure the volume of a confined gas in a closed syringe inside a 0.5 liter plastic soft drink bottle. Pressure will be increased by using a Fizz-Keeper©. . Materials: 1 Disposable 3 ml syringe, modified 1 Syringe Tip Cap Small amount silicone lubricant (Stopcock Grease) 1 Fizz-Keeper ©. 1 plastic soft drink bottle, 0.5 liter Directions: 1. Remove the plunger from the syringe and apply a thin application of silicone lubricant

to the black part of the plunger. Reinsert the plunger into the syringe. 2. Adjust the position of the plunger to the 3.0 ml mark. 3. Place the syringe cap on the syringe trapping 3.0 ml of air in the syringe. 4. Place the syringe in the soft drink bottle and screw the Fizz-Keeper © on the bottle.

Record the beginning volume as 3.0 ml. 5. Increase the pressure in the bottle by pumping the Fizz-Keeper © 10 times. Read the

volume of the air in the syringe. 6. Pump 10 more times and record the volume. Continue pumping 10 time and reading

the volume for a total of 10 volume readings. 7. Plot a graph of pressure (# of strokes) vs. volume. Data Table:

Teachers Guide Purpose: To give students a first-hand experience with Boyle’s Law Scope & Sequence: Can be used to 1ntroduce Boyle’s Law in the unit on gas laws or to follow - up shortly after the textbook introduction. Preparation & Tips: Cut off the “wings” at the top of each syringe. Fizz-Keepers may be purchased at discount stores. They are also available from Flinn. Hazards: Release pressure by twisting the cap slowly at end of the measurements. Disposal: None. Keep syringes & syringe caps for next year. Reference: Rohrig, Brian. 39 FANTASTIC EXPERIMENTS WITH THE FIZZ-KEEPER

PRESSURE (#STROKES) 0 10 20 30 40 50 60 70 80 90 100

VOLUME OF AIR 3.0

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Acid Deposition Simulation

Background: This lab provides students the opportunity to observe noxious oxides that are a major fac-tor in pollution that otherwise could not be observed in a high school laboratory. Optional exercises permit the student to design his ova environment and to be able to observe fac-tors that effect pollution. The atmosphere is a warm blanket that helps to maintain conditions suitable for life as we know it. Oxygen is one of the most important elements in the atmosphere because organ-isms need oxygen to stay alive. Oxides are binary (two elements) compounds containing oxygen and one other element. They are abundant in the earth's crust. Three major categories of oxides that are also air pollutants are: 1. Carbon oxides (CO2 and CO) Carbon dioxide and carbon monoxide are produced by the combustion of organic materi-als, primarily gasoline and other fossil fuels. 2. Oxides of sulfur (SO2 and SO3) Sulfur compounds, mostly S02, are among the most unpleasant and harmful of the com-mon pollutant gases. About 80 % of all the S02 generated comes from the combustion of fossil fuels. They are also produced by burning coal and from oil refineries. These com-pounds form acids in moist air.

S (s) + O2 (g) → SO2 (g)

Sulfur dioxide may be oxidized to S03 by any of several pathways.

2 SO2 (g) + O2 (g) → 2 SO3 (g)

Once SO3 is formed it dissolves in water droplets, forming sulfuric acid.

SO3 (g) + H2O (l) → H2SO4

This what happens when fuel containing sulfur is burned. 3. Oxides of nitrogen (NO2, etc.) come from fuel burning (power plants and automobiles).

In all combustion reactions in the air, nitrogen combines with the oxygen.

N2 (g) + O2 (g) → 2 NO (g) Nitric oxide (NO) reacts readily with O2 to form NO2 when exposed to the air. 2NO (g) + O2 (g) → 2NO2 (g)

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Acid Deposition Simulation

When dissolved in water, N02 forms nitric acid. 3 NO 2(g) + H2O (l) → 2 HN)3 (aq) + NO (g) The combustion in the automobile is the worst offender. At the high temperatures of the automobile engine NO is formed. NO acts as a catalyst for ozone destruction and is in-volved in the production of smog in addition to the acid rain production. The amounts of nitrous oxides can range from 1 gram per km (kilometer driven) for a new passenger car to over 20 grams per km (kilometer driven) for an old diesel truck. The anthropegenic (man-made) nitrous oxides are large amounts compared with the natural emissions such as those from forest fires. Amounts are increasing as the global consumption of fossil fu-els and the number of cars, trucks and SUVs increase. The geographic distribution of ni-trous oxide emissions reflects large power plants and population density in the northeast-ern United States and California. Nitrogen dioxide (NO2), the brownish-yellow gas in pol-luted air, causes respiratory distress and reacts with substances in the atmosphere to form toxic compounds. Purpose: Using methods of small -scale chemistry demonstrated by Dr. Steven Thompson of the Department of Chemistry of Colorado State University, noxious oxides of sulfur and nitro-gen will be generated and their contribution to acid rain will be observed. Materials: ( Per two students) Chemicals: Reagents needed in disposable Beral pipets.

0.5 M Potassium nitrite (KNO2) 2.0 M Sulfuric acid (H2SO4) 0.5 M Sodium sulfite (Na2SO3) Distilled water colored with 0.03% Bromcresol green 2.0 M NH3 (aq). Or Household Ammonia

Equipment: Two polystyrene Petri dishes with access port sealed with scotch tape, white grid paper Precautions/Hazards:

Goggles and aprons should be worn when using chemicals. Since trace amounts of SOx and NOx gases will be generated Petri dishes should be opened and closed only according to directions. Be sure to terminate the NOx and SOx gases, as directed with ammonia when finished. Care should be taken when using solutions of acids and am-monia.

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Acid Deposition Simulation

Procedure:

1. Prepare each Petri dish by heating the tip of a triangular file, glass rod or nail, or heat an old soldering iron. Use to melt a hole (access port) about 1 cm from the outside rim of the Petri dish. THIS MAY BE DONE BY THE TEACHER. Seal the port with scotch tape. Place two clean dry Petri dishes with sealed access ports on the grids. At the po-sitions indicated drop the following solutions:

Dish 1 (control) 1 drop 0.5 M KNO2

2 drops 0.5 M Na2SO3 2 drops distilled water with 1 drop acidity probe (0.03% bromcresol green sol)

Dish 2 1 drop 0.5 M KNO2 2 drops 0.5 M Na2SO3 2 drops distilled water with 1 drop acidity probe (bromcresol green)

Hazards: CAUTION: Wear goggles and aprons.

2. In dish 1 and dish 2 add drops of Na2SO3, KNO2 and bromcresol where indicated. 3. In dish 2 generate SOx and NOx by adding 2 drops of 2M H2SO4 first to Na2SO3 and

then to KNO2 by rotating hole in top of petri dish and removing tape and replacing tape first over Na2SO3, and then KNO2.

4. Observe the acidity probe. What color does bromcresol green turn in the presence of an acid? Compare with Control. What acids do you think were formed?

5. Stop the reaction by lifting the portal tape and adding 1 drops of ammonia.

KNO2 KNO2

Na2SO3Na2SO3

Bromcresol Bromcresol

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The Dynamic Duo

Acid Deposition Simulation

Disposal: Use a wash bottle to flood the system with water at the sink. Rinse Petri dish with distilled water and dry with paper towel. Long Term Project: You are a research scientist preparing studies of acid rain. In Petri dishes prepared like the ones above, design experiments using what you have learned from this lab and using chemicals from this lab to (1) compare the rates of transport of SO2 compared to NOx <Hint: use a succession of acidity probes radiating out from the source noxious gases to determine the rate of transport (how fast it moves). (2) Prepare a graph to show the aver-age of several experiments (3) Set up sinks, chemical barriers that might affect the move-ment. This could include sandy areas, grasslands, golf courses, styrofoam or different rock like limestone or quartz, lakes. Keep the area under the port in the Petri dish clear so you can add more acidity probes to monitor acidity over a period of time. Record your data and compare with other microenvironments to draw conclusions. Write a short ab-stract and summary for your project. Write a short hypothesis for each attempt and a con-clusion based on your experimentation. Include what areas are in most danger by acid deposition. Report on the Properties of Oxides (Enrichment) 1. Write the equations for the oxidization of sulfur dioxide to sulfur trioxide and for the

formation of the acid when the sulfur trioxide comes in contact with water. 2. From the results of the acidity probe after the addition of aqueous ammonia to the

above reaction, explain why aqueous ammonia can terminate the production of sulfu-ric acid.

3. Why does unpolluted rain have a pH of about 5.5? 4. Acid deposition is primarily caused by the oxidation of what substances? 5. Why is the atmosphere very sensitive to anthropogenic (man made as opposed to

natural) pollution? 6. Which gaseous air pollutants are the precursors to acid deposition? 7. What are natural buffers present in lakes that can neutralize acid deposition? 8. In North America acid deposition appears to be a more serious environmental prob-

lem in northeastern USA and northeastern Canada than elsewhere. What factors are responsible for this regional imbalance?

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The Dynamic Duo

Acid Deposition Simulation

9. How much nitrous oxide per km does a new car exhaust into the atmosphere Answers to Report on the Properties of Oxides:

1. 2 SO2 + O2 → 2 SO3 SO3 + H2O → H2SO4 2. Aqueous ammonia is basic. 3. Unpolluted rain is saturated with atmospheric carbon dioxide and thus has a pH of

5.6. 4. Oxidation of carbon, nitrogen, and sulfur causes acid reposition. 5. Anthropogenic pollution is of a much greater magnitude and is increasing. Also, the

atmosphere is more sensitive because it is a much smaller reservoir than the litho-sphere or hydrosphere.

6. Key atmospheric pollutants are sulfur and nitrous oxides. 7. Buffers in lakes are calcium and magnesium bicarbonate and organic acids entering

from the watershed. 8. Highest emissions of nitrous oxides occur in northeastern. US population density is

greater as is use of the automobile. 9. 1 gram nitrous oxide per km (kilometer) driven. References: Thompson, Steven (1989) Woodrow Wilson National Fellowship) Foundation Chemistry in the Environment, Princeton University, Princeton, New Jersey. Wagner, Maxine (1983) "Laboratory Manual for Chemistry" I ). 87-89. Cebco, Newton, Massachusetts.

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The Dynamic Duo

Electrolysis

Introduction: Some oxidation—reduction reactions do not occur spontaneously. They can be driven by electric energy. An electrolytic cell changes electrical energy into chemical energy by forcing a reaction to take place which would not take place otherwise. This process where an electric current is used to drive a chemical reaction is called electrolysis. The electro-lytic cell is made�up of a pair of electrodes, an electrolytic solution, a container and a bat-tery or power supply connected to the electrodes. In the electrolytic cell the reduction oc-curs at the negative electrode which is called the cathode. Oxidation occurs at the positive electrode which is called the anode. These reactions at the electrodes complete the elec-tric circuit and allows electric energy to be transferred from the battery to the electrolytic cell. During the electrolysis of H2O, the following reactions occur. 2 H2O (1) + 2 e- → H2 (g) + 2 OH- (aq) 2H2O (1) → O2 (g) + 4 H+ (aq) + 4 e- Materials: Battery, 0.1M Na2SO4 with Bromothymol Blue indicator to produce a green color, phenophthalein, 600 ml beaker or cut off 2 or 3 liter bottle with flat bottom, 2 small test tubes(75 x 100 mm), 9 V battery. Procedure: Fill the 600 ml beaker about 3/4 full with Na2SO4. Take 2 small test tubes and fill with solution in beaker allowing them to stay under solution. Set the wax coated 9 V battery on bottom of the beaker of Na2SO4 with bromothymol blue indicator. The solution should b green in color. Carefully move the test tubes into an upside down vertical position over battery terminals without losing liquid. Note which test tube is over which terminal. Allow some metal of each terminal to be exposed. As soon as you can see a difference in color and water level in test tubes, put a finger over the end of each tube and lift each out. Re-cord color of tubes and ratio of gas in tubes. Remove battery and rinse with water. Return Na2SO4 to the wand Na2SO4 container to be recycled. Questions: 1. Compare the volume of gas collected at the (+) electrode to the volume of gas col-

lected at the (-) electrode. 2. What color is the solution at (-) electrode? What does this indicate about the pH of the

solution is this test tube? Is this the anode or the cathode? 3. What color is the solution at (+) electrode? What does this indicate about the pH of the

solution in this test tube? Is this the anode or the cathode? 4. Write balanced equations for the two half reactions and the overall equation for the

electrolysis of water.

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The Dynamic Duo

Molar Mass of Butane

Purpose: To determine the molar mass, simplest formula and molecular formula of butane Suggested Topics For This Activity: Avogadro’s Hypothesis, Simplest & Molecular Formulas, Ideal Gas Law Background Information: Avogadro’s Hypothesis states that equal volumes of 2 gases at the same temperature and pressure contain equal numbers of molecules. For example: The molar mass of hydrogen is 2.0 g. If a sample of hydrogen gas has a mass of 4.00 g and a same volume of gas X has a mass of 60 g, then by a simple ratio we can find the molar mass of gas X. In this lab, the same idea is used where you will find the masses of 2 equal volumes of 2 different gases, air (molar mass = 28.9 g) and butane (molar mass to be found.) Using a syringe, one can measure the volume of a gas very accurately. In this lab we will use a can of bu-tane used to refill lighters as the source of butane. We used Ronson brand from Wal-Mart. You may have to ask for it. By measuring the temperature, the pressure of the butane and the mass of the butane, the Molar Mass of the Butane can be calculated using the Ideal Gas Law. PV = nRT. Precautions: Dispense and dispose of butane under hood. Wear goggles and apron. No open flames. Use the same syringe and Luer cap Materials: Refill can of butane, 60 ml syringe lubricated with silicone lubricant, analytical balance ac-curate at least to .01 of gram, piece of plastic or rubber tubing 1/8 ID 2 cm long icemaker tubing), thermometer, barometer Procedure: Find the mass of the empty syringe with Luer cap on.- Zero volume Using the same syringe, take the cap off and fill the syringe with 60 ml of air. Put on cap. Find the mass. Record. Empty the syringe of air. Working in the hood, fill the same syringe with 60ml butane by attaching the piece of tubing to the end of the butane can. Place the other end of the tub-ing on the tip of the syringe. Push down on the syringe until you have 60ml of butane in the syringe. Recap the syringe. Find the mass of the capped syringe which is filled with butane and record.

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The Dynamic Duo

Molar Mass of Butane

Take the barometric reading. Take the temperature of the air. Calculations: 1. From your data find the mass of air and the mass of butane. 2. If the molar mass of air is 28.9 g, find the molar mass of butane. 3. If butane is 82.8 % carbon and 17.2 % hydrogen, find the simplest formula of butane. 4. Find the molecular formula of butane. 5. Using the mass of the butane, the barometric reading, volume of butane and the tem-perature and the Ideal Gas Law, calculate the Molecular Mass of the butane. Use the Molar Mass calculated from atomic weights to determine the % error in the molar mass of butane calculated in calculation # 4 and Calculation # 5. Questions: 1. What are we assuming about the butane in the can? 2. Compare the Molar Mass of butane calculated by the two methods. Reference: Alan Slater, Chem Ed, 2001

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The Dynamic Duo

Micro-Titration Apparatus