microgravity zeolite crystal

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Microgravity A Teachers Guide with Activities in Science, Mathematics, and Technology,

EG-1997-08-110-HQ, Education Standards Grades 58 (

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Zeolite Crystal GrowthObjective:

To grow zeolite crystals and

investigate how gravity affectstheir growth.

Science Standards:Science as InquiryPhysical ScienceUnifying Concepts and ProcessesChange, Constancy, & MeasurementScience in Personal and Social

Perspectives

Science Process Skills:ObservingCommunicatingMeasuringCollecting DataControlling VariablesInvestigating

Mathematics Standards:Measurement

Activity Management:The preparation of zeolite crystals,although not difficult, is an involvedprocess. A number of differentchemicals must be carefully weighedand mixed. You may wish to preparethe chemicals yourself or assignsome of your more advancedstudents to the task. Refer to the

materials and tools list on the nextpage for a detailed list of what isrequired.

This activity involves maintaining ahot water bath continuously for up to8 days. If you do not have thefacilities to do this, you can conduct

Zeolite crystals are being grown in a hot waterbath.

the experiment for just the 0 and 1 TEA(triethanolamine) samples described below.Crystals may also be formed if the hot water bathis turned off at the end of the school day andturned on the succeeding day. Crystallization

times will vary under this circumstance, and closemonitoring of the formation of the crystallineprecipitate will be necessary.

Following the growth of zeolite crystals, smallsamples can be distributed to student groups formicroscopic study.

Procedure:1. While wearing hand and eye protection, weigh

0.15 grams of sodium hydroxide and place it ina 60 ml, high-density polyethylene bottle. Add60 ml of distilled water to the bottle and cap it.Shake the bottle vigorously until the solids arecompletely dissolved. Prepare a second bottleidentical to the first.

2. Add 3.50 grams of sodium


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metasilicate to one of the bottles and again cap itand shake it until all the solids are dissolved.Mark this bottle silica solution. To the second

bottle, add 5.6 grams of sodium aluminate andcap it and shake it until all the solids aredissolved. Mark this bottle alumina solution.3. Using a permanent marker pen, mark the four,30 ml high-density polyethylene bottles with thefollowing identifications: 0 TEA, 1 TEA, 5 TEA, and10 TEA.

Sodium aluminate NaAIO2

FW=81.97Sodium metasilicate anhydrous,

purum, Na2O

3Si, FW=122.06

Sodium hydroxide pellets,97+%, average compositionNaOH, FW=40Triethanolamine (TEA), 98%(HOHCH

2)

3N, FW=149.19

Distilled water1000 ml Pyrex glass beakerAluminum foilMetric thermometer with range up

to 100CLaboratory hot plate

2-60 ml high-density polyethylenebottles with caps

4-30 ml high-density polyethyenebottles with caps

Plastic glovesGogglesGlass microscope slidesPermanent marker pen for

marking on bottlesWaterproof tape

Lead fishing sinkersTongsEyedropperOptical microscope, 400X

MATERIAL

S

AND

TOOLS

4. Place 0.85 grams of TEA into the bottle marked1 TEA. Place 4.27 grams of TEA into thebottle marked 5 TEA. Place 8.55 grams ofTEA into the bottle marked 10 TEA. Do notplace any TEA into the bottle marked 0 TEA.

5. Add 10 ml of the alumina solution to each of

the bottles. Also add 10 ml of the silica solutionto each bottle.6. Cap each bottle tightly and shake vigorously.

Secure each cap with waterproof tape and tapea lead sinker to the bottom of each bottle. Thesinker should weigh down the bottle so it willbe fully immersed in the hot water.

7. Prepare a hot water bath by placing approxi-mately 800 ml of water in a 1000 ml Pyrexsbeaker. Place the four weighted bottles into thebeaker. The bottles should be covered by the

water. Cover the beaker with aluminum foil andpunch a small hole in the foil to permit a metricthermometer to be inserted. Fix the thermom-eter in such a way as to prevent it from touch-ing the bottom of the beaker. Place the beakeron a hot plate and heat it to between 8$ and95 C. It will be necessary to maintain thistemperature throughout the experiment.Although the aluminum foil will reduce evapo-ration, it will be necessary to periodically addhot (85 to 90 C) water to the beaker to keep

the bottles covered.8. After 1 day of heating, remove the bottle

marked 0 TEA from the bath with a pair oftongs. Using an eyedropper, take a smallsample of the white precipitate found on thebottom of the bottle. Place the sample on aglass microscope slide and examine for thepresence of crystals under various magnifica-tions. Make sketches or photograph anycrystals found. Be sure to identify magnifica-

tion of the sketches or photographs and esti-mate the actual sizes of the crystals. Determinethe geometric form of the crystals. Look forcrystals that have grown together.


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9. Repeat procedure 8 for the 1 TEA bottle after 2days of heating. Repeat the procedure again forthe 5 TEA bottle after 5 days and for the 10 TEAbottles after 8 days. Compare the size, shape,and intergrowth of the crystals formed in eachof the bottles.

AssessmentCollect student sketches and written descriptionsof the zeolite crystals.

Extension:1. Obtain zeolite filter granules from a pet shop.

The granules are used for filtering ammoniafrom aquarium water. Set up a funnel with filterpaper and fill it with the granules. Slowly poura solution of water and household ammonia

(ammonia without lemon or other maskingscents) into the granules. Collect the liquidbelow and compare the odor of the filteredsolution and the unfiltered solution. Try runningthe filtered solution through a second time andagain compare the odors. Be sure to wear eyeprotection.


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Zeolites are crystals made up of the elementssilicon, aluminum, and oxygen. The crystalsconsist of alternatingarrays of silica (beachsand, SiO

2) and alumina

(aluminum oxide, Al20

3)

and can take on manygeometric forms such ascubes and tetrahedra.Internally, zeolites are rigidsponge-like structures withuniform but very small

openings (e.g., 0.1 to 1.2nanometers or 0.1 to 1.2 X10-9 meters). Because ofthis property, theseinorganic crystals aresometimes calledmolecular sieves. Forthis reason, zeolites areemployed in a variety ofchemical processes. Theyallow only molecules of

certain sizes to enter theirpores while keepingmolecules of larger sizes out. In a sense, zeolitecrystals act like a spaghetti strainer that permitshot water to pass through while holding back thespaghetti. As a result ot tnis filtering action,zeolites enable chemists to manipulate moleculesand process them individually.

The many chemical applications for zeolite

crystals make them some of the most usefulinorganic materials in the world. They are used ascatalysts in a large number of chemical reactions.(A catalyst is a material that has a pronounced

Student Reader- 1

Zeolites

effect on the speed of a chemical reaction withoutbeing affected or consumed by the reaction.)

Scientists use zeolitecrystals to produce allthe worlds gasolinethough a chemicalprocess called catalyticcracking. Zeolite crystalsare often used infiltration systems forlarge municipalaquariums to remove

ammonia from thewater. Because they areenvironmentally safe,zeolites have been usedin laundry detergents toremove magnesium andcalcium ions. Thisgreatly improvesdetergent sudsing inmineral-rich hardwater. Zeolites can also

function as filters forremoving low

concentrations of heavy metal ions, such as Hg,Cd, and Pb, or radioactive materials from wastewaters.

Although scientists have found many beneficialuses for zeolites, they have only an incompleteunderstanding of how these crystals nucleate(first form from solution) and grow (becomelarger). When zeolites nucleate from a watersolution, their density (twice that of water) causesthem to sink to the bottom of the specialcontainer (called an autoclave) they are growing


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Student Reader- 2

in. This is a process called sedimentation, and itcauses the crystals to fall on top of each other. Asthese crystals continue to grow after they havesettled, some merge to produce a large number ofsmall, intergrown zeolite crystals instead of

larger, separate crystals.

Zeolite crystal growth research in themicrogravity environment of Earth orbit isexpected to yield important information forscientists that may enable them to produce betterzeolite crystals on Earth. In microgravity,sedimentation is significantly reduced and so isgravity-driven convection.

Zeolite crystals grown in microgravity are often ofbetter quality and larger in size than similarcrystals grown in control experiments on Earth.Exactly how and why this happens is not fullyunderstood by scientists. Zeolite crystal growth

experiments on the Space Shuttle and on thefuture International Space Station should provideinvaluable data on the nucleation and growthprocess of zeolites. Such an understanding maylead to new and more efficient uses of zeolitecrystals.


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Name: _______________________

Instructions:Observe through a microscope each zeolite crystal sample provided to you by your teacher. Sketch thesamples in the circles provided and write a brief description of what you see.

Sample 1

__________________ TEA

Sample age ________________ day(s)

Description:

Sample 2

__________________ TEA

Sample age ________________ day(s)

Description:

Microscopic Observation ofZeolite Crystals

Student Work Sheet - 1

Magnification: ____________ X



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Student Work Sheet - 2

Sample 3

__________________ TEA

Sample age ________________ day(s)

Description

Sample 4

__________________ TEA

Sample age ________________ day(s)

Description

QUESTIONS:

1. What geometric form (crystal habit) did the zeolite crystals assume as they grew? Was there morethan one form present? How did the zeolite crystals appear when they grew into each other?

2. Can you detect any relationship between the length of time crystals were permitted to form, theirsize and their geometric perfection?

3. Would additional growing time yield larger crystals? Why or why not?



microgravity zeolite crystal

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