Space for Growth: Colloidal Crystallization in …bwagenbo/MISEPCapstoneProject.pdfWagenborg 3 Space...

Bill Wagenborg

MISEP 2

Capstone Project

Summer 2008

Space for Growth: Colloidal Crystallization in Microgravity

Overview My capstone project has been an interesting and fulfilling journey. I produced a

high quality informative piece on colloids, while discovering what is involved in the

formulation of a true scientific content paper. Then I used this knowledge to create a full

detailed unit plan around microgravity that would be beneficial to middle school students.

Most of all, I was able to take away the experience of working with my content reader,

who was a true expert in his field. Through his knowledge I learned about an area in

science that in reality I did not know existed before I began this process, but now view it

with the utmost respect.

Ever since I was a child I have had a fascination with outer space. I have often

wondered what it would be like to travel there and to experience the effects of

microgravity. This, combined with the fact that my students always had a lot of questions

around the subject, helped me to choose in the fall of 2007 my original capstone project

topic, The Effects of Space Travel on The Human Body. There was one problem though;

a content reader could not be found for this topic. Finally in the spring of 2008, I was

notified that Dr. Arjun Yodh, The James M. Skinner Professor of Science in the Physics

and Astronomy Department of the University of Pennsylvania, would be interested in

working with me. Dr. Yodh has done research and experiments revolving around

colloids and their behavior in microgravity. He currently has experiments waiting to be

done on future space missions. I could not pass up the opportunity to work with someone

so knowledgeable and respected, so I decided to change my topic to Colloidal

Crystallization in Microgravity.

Colloidal suspensions are not something that I have had a lot of experience with

as a student or in my teaching career. In fact, colloids are covered in one paragraph in the

Wagenborg 2

textbook I use for teaching matter to my eighth grade students. Through Dr. Yodh’s

guidance, I was able to develop an understanding of colloidal suspensions and gain an

appreciation for microgravity as a science. I am now able to explain the importance of

colloidal science in our world and how it will play an important part in our future.

My content piece was developed in a way that will enable the reader to gain a

solid understanding of colloids and their behavior in microgravity. It is written in two

parts: colloidal behavior in gravity and colloidal behavior in microgravity. I begin by

explaining what a colloidal suspension is and the common examples of them in our

world. I then discuss the history of colloidal studies and why investigation of them is an

important part of science. The interaction and phase change of colloidal particles on Earth

is the next part of my paper. This section is crucial because it will serve as a comparison

when discussing microgravity. This entire first half of my paper has led up to my

discussion of colloidal behavior in microgravity. I begin this second part by explaining

what microgravity is and how it is created. The focus then shifts to recent and current

colloidal exploration in space. I conclude my content piece by discussing the impact of

the research done on colloidal crystallization in microgravity.

My pedagogy section is based on the backwards design model by Wiggins and

McTighe (2005). In this model, the educator looks at what the desired results are of the

unit and then decides how they are going to have the students achieve them. Colloidal

crystallization is a much higher level of content than I would teach to my middle school

students. I wanted to keep the microgravity theme because I teach astronomy and I know

most middle school students enjoy the topic. My unit revolves around the students

understanding how microgravity is created, how it affects the behavior of different

objects and how models allow us to study certain phenomena that are impossible to

recreate. My activities are hands on, follow an inquiry format and are relevant to today’s

world.

Completed during the summer of 2008, I present my capstone project.

Wagenborg 3


What is a Colloidal Suspension?

Colloid suspensions are composed of small solid particles, dispersed and

suspended in a liquid. (Cheng, et. al, 2001). Thomas Graham coined the term in 1861,

which in Greek means glue, based on his observations of the low diffusion rate of

particles in suspension (Antonietti, 2008). Typically the suspended particles are large

enough to scatter light yet cannot be separated by coarse filtration (Holt, 2004). As shown

in Figures 1 and 2, colloidal particles are about 1/100 the thickness of a human hair

(ranging from 50nm to 5um) and can be found in many common materials such as paints

and inks. Mayonnaise and milk are colloidal materials too; in this case where the particles

are made of another liquid, oil, and are suspended in a liquid. Smoke is also a kind of

colloidal dispersion where solid soot particles are suspended in air. Colloidal suspensions

differ from traditional solutions such as water-sugar mixtures in which sugar molecules

are actually dissolved in water (Pellis & North, 2004).

(1) (2)

Figure 1: The Left Image shows an electron micrograph of an aggregate of several particles.

Figure 2: The Right Image is an optical microscope image of many micron-sized colloidal particles that

form a colloidal glass; the black cylinder is a magnetic probe moves within the colloidal glass.

Wagenborg 4

Colloidal Studies

Colloidal Science crosses over physics, biology, chemistry and other fields in

science (Hiemnz & Rajagopalan, 1997, 2). Investigation and experimentation with

colloids traces its history back to the late nineteenth century. Brownian motion was

discovered around this time. Brownian motion refers to the ability of micron size

particles dispersed in a liquid to be in a constant state of random motion. Back then

people were puzzled by how this could happen, if the particles were not living. This was

also about the time when the existence of molecules was being hotly debated. In

Einstein’s Brownian motion theory paper he noted, “according to the molecular –kinetic

theory of heat, bodies of microscopically size suspended in a liquid will perform

movements of such magnitude that they can be observed in a microscope” (Einstein,

1905, 1). Thus, the independent ‘random’ motion is caused by the molecular nature of

matter and is not substantially affected by composition or density of the particle. Jean

Perrin carried out detailed experiments on Brownian motion confirming Einstein’s

theories and concluded that smaller particles, less viscous fluids and higher temperatures

increase the amplitude of the colloidal particle motions (Russel, 1989, 65).

Although colloids found many useful applications, fundamental interest in colloid

science waned by World War II. This situation, however, changed starting in the decade

of the 1960’s as new problems and experimental techniques emerged. These

developments along with an increased understanding of fluid mechanics and the

availability of diversity of monodisperse model suspensions led to new uses and

experimentation with colloids (Russel, et. al, 1989, xii).

Colloidal Suspensions as a Macroscopic Model of Atoms

All materials are made up of atoms, and therefore it is desirable to understand

material structure at the atomic level. In principle, material properties (e.g. weight, color,

density, mechanical strength, conductivity etc.) depend on how the atoms of the material

are arranged and how they interact. Colloidal suspensions can provide scientists with a

macroscopic model for this atomic behavior, where the particles play the role of the

atoms. By understanding the behavior of colloidal crystals, for example, scientists gain

Wagenborg 5

insight into basic solid state and condensed matter physics and also learn how to create

new materials through “Colloidal Engineering” (Cheng et.al, 2001).

This paper will focus on the model systems. Colloidal particles in suspensions

move around, interact with one another and are acted on by thermal forces in equilibrium.

These thermal forces exerted by the fluid on the particles are responsible for Brownian

motion. Left alone, the suspensions evolve towards their lowest free energy state (van

Blaaderen & Wiltzius, 1997). If the particles interact like hard spheres (i.e. no force acts

on them unless they touch), then in equilibrium they arrange themselves in such a way

that each particle has the maximum amount of space or free volume to move (Freeman-

Hathaway, 2002). By studying colloidal crystals, we can gain knowledge about how and

why the particles self assemble, about the relation of this self organization to the forces

between particles in suspension and about many body effects. The model colloids can be

tracked by video microscopy which is impossible for atomic structures (Velev, et. al,

2000).

Colloidal suspensions differ from atomic structures in three major ways. The first

is that since the solvent fixes the sample volume, crystallization occurs at a fixed volume

rather than a fixed pressure. Secondly, since energy and momentum are exchanged

between the particles and the solvent, “only particle conservation should govern the large

time dynamics of the system” (Cheng et. al, 2001, 4146). Thirdly, any latent heat that is

created is not important because of the small number of particles and the quick energy

exchanges with the solvent (Cheng et. al, 2001).

The Interactions and Phases of Colloidal Particles in Suspension

At the beginning of the twentieth century, Perrin came to the conclusion that the

particles in a dilute colloidal suspension behaved like an ideal gas (Lekkerkerker &

Stroobants, 1998). At higher concentrations of particles, the manner in which the

colloidal particles interact, their stability and their phase behaviors can be changed

through the manipulation of their composition and the composition of the solvent. Some

of the forces that arise between particles in suspension are van der Waals attractions

(dispersion forces), electrostatic (Coulomb) repulsion and attraction, hard sphere

repulsion and entropic forces; other forces acting on the particles can be gravity or

Wagenborg 6

applied electronic and magnetic fields (Russel, 1989). Colloidal crystals are classified as

a soft condensed matter because of their low elastic constraints; they are easily deformed

by interaction with applied force fields such as shear (van Blaaderen et. al, 1997).

Van der Waals forces, as shown in Figure 3, are created by molecular interactions

due to the permanent polarity in the molecules created by the electric fields of other

molecules. These forces generally cause the particles to attract to one another so that they

will sometimes form clusters and aggregate as a result. These aggregates “retain their

identity but lose their kinetic independence” (Hiemnz& Rajagopalan, 1997, 465).

Aggregation demonstrates an attraction between the particles (Hiemnz & Rajagopalan,

1997).

(3)

Figure 3: Negatively charged colloidal particles in suspensions containing positive counter-ions. The

fluctuating polarity of each particle causes an attraction which is the van der Waals force.

Electrostatic repulsion in a colloidal system is responsible for, among other

things, the long shelf life of latex paint (Russel, 1989, 88). This force can be affected by

the addition or subtraction of ions in the suspension (Russell, 1989, 1). According to the

theory of Derjaguin, Landay, Vervey and Overbeek (DLVO), “isolated particle pairs of

like charged (i.e. both positively or both negatively charged) colloidal spheres in an

electrolyte should interact in a “purely repulsion screened electrostatic (Coulombic)”

force (Bowen and Sharif, 1998, 663). Colloidal stability, according to this theory, is

based on a balance of van der Waals attractive forces and repulsive electrical double layer

Wagenborg 7

forces. Some recent experiments have found that this theory works for low concentrations

of particles but may not work for higher concentrations (Bostrom et.al, 2001).

Sometimes particles interact like hard spheres. Hard spheres have no interaction

energy when they are apart, but have an infinite amount when they are touching. Thus

they behave like marbles or billiard balls at the microscopic scale. These suspensions can

be produced if van der Waals attractions are reduced because of the refractive index

matching solvent and when steric stabilization is caused by a thin layer of polymer

attached to the surface of the spheres (Cheng et. al, 2001).

Even in this very simple system of colloidal hard spheres, as the particle

concentration is increased, the particles will arrange themselves into different structures.

At lowest concentrations, gases or fluids of particles form. At higher concentrations, a

fluid coexists with a crystal, and when concentrations are at a volume fraction well above

50%, a fully crystallized sample or a semi crystallized glassy appearance forms (Pusey,

1986). This data is represented in Figure 4.

In early experiments on Earth, samples that were the most diluted (i.e. volume

content fraction below 0.494) exhibited no signs of change over time. It was theorized

that at this “concentration the particles are spatially arranged like atoms in a dense liquid,

exhibiting considerable short range positional ordering” (Pusey, 1986). Samples with

higher concentration levels (i.e. volume fraction content between 0.494 and 0.545)

produced a coexistence of fluid and crystal. At even higher concentrations (i.e. volume

content fraction above 0.545 or above the volume fraction of melting) crystals form

(Yodh, 2007). The structure of these crystals was determined to be a combination of face

centered cubic and hexagonally close packed planes (Zhu et. al, 1997). Samples produced

on Earth that were the most concentrated (i.e. volume content fraction close to 0.637)

exhibited only partial crystallization. This was still the case after the samples were left

undisturbed for several months. Sometimes the particles were described to be arranged as

in a disordered glass (i.e. colloidal glass). It was believed that the high concentration

caused problems with particle diffusion, which resulted in the particles not crystallizing

on the experimental timescale (Pusey, 1986). There is also competition with equilibrium

processes due to particle sedimentation. When concentration level is at a volume content

Wagenborg 8

fraction of around 0.74 the face cubic centered crystal structure has the lowest free

energy and should form (Zhu et. al, 1997). These results are shown in Figure 5.

(4)

Figure 4: Predicted phase behavior of particles as a function of volume fraction. Notice the

suspension changes from a liquid to a solid with a very small change in particle concentration (i.e.

volume fraction).

(5)

Figure 5: Colloidal Hard Spheres. From left to right as particle concentration increases,

phases change from liquid to a coexistence of liquid and crystal to crystal alone to a glassy

appearance. Bright colors indicate that a crystal has formed; the color reflected depends on the

spacing of the planes of the colloidal crystal.

Wagenborg 9

In the hard sphere model, colloidal crystallization is driven by entropy alone and

constrained by the number of packings possible at high densities (Cheng et. al., 2001).

Entropy is the driving force for disorder in nature (Eldridge, et.al, 1993). According to

the Second Law of Thermodynamics, “any spontaneous change in a closed system results

in an increase of entropy” (Frenkel, 1999, 26). In equilibrium all physical systems will try

to minimize their free energy, F= E (or sometimes called U)-TS, where E (or U) is the

sample internal energy, T is the temperature and S is the sample entropy (Yodh, 2007)

(Frenkel, 1999). Using this formula a system (at constant temperature) can lower its free

energy by increasing the entropy or decreasing internal energy. Stable phases are those

with the lowest free energy (F). When a phase change takes place, at a given particle

concentration and temperature, from a fluid (disordered) to a solid (order), for example,

loss of entropy can be offset by the greater change of internal energy. This type of

transition is internal energy driven and is common in many atomic and molecular

materials (see Figure 6). It may be more beneficial to study the hard sphere systems since

they expose the effects of entropy alone and thus test our understanding of basic

statistical physics.

(6)

Figure 6: Colloidal Hard Spheres. From left to right as particle concentration increases,

phases change from liquid to a coexistence of liquid and crystal to crystal alone to a glassy

appearance. Bright colors indicate that a crystal has formed; the color reflected depends on the

spacing of the planes of the colloidal crystal.

Wagenborg 10

Recently, research has shown convincingly that in the hard sphere colloidal

systems, the phase changes are in fact entropy driven (See Figure 7for hard sphere

interaction potential). If the crystallization occurs at constant density, entropy may be

higher in the solid phase than in the corresponding disordered phase. In this case, the

particles in crystals are packed more efficiently and in turn have more room to move (or

more free volume) (Frenkel, 2006).

(7)

Figure 7: Left panel is interparticle potential for hard spheres (zero when apart, infinite

when touching). In this system the system free energy is dependent on entropy alone

Another example of entropic forces in action arises in suspensions of large and

small diameter hard spheres. In this mixture of different sized particles, “an ordered

arrangement of large spheres can increase the total entropy of the system by increasing

the entropy of the small spheres” (Yodh, 2006). For the smaller spheres entropy is

dependent on the number of positions it can occupy in the mixture (or the free volume per

small particle). The more positions a small sphere can occupy in a container, the more

free volume and the more entropy it will have. Since the smaller spheres cannot penetrate

close to the large spheres, there is a forbidden boundary around each of the hard spheres.

When the large hard spheres move closer to each other, this forbidden boundary overlaps

which creates more free volume for the small spheres in the container (see Figure 8).

Thus, the entropy of the entire colloidal suspension is increased by the ‘ordering’ of the

larger spheres. The entropic interaction between large spheres due to the presence of

small spheres is also known as attractive depletion (Yodh, 2006).

Wagenborg 11

(8)

Figure 8: This figure shows how the smaller spheres have more free volume when the large

spheres overlap. The blue regions correspond to ‘positions’ where the small particles cannot go. The red

regions correspond to the gain in free volume experienced by the small particles when the spheres touch

each other or the wall. In this case the entropy has increased for the entire suspension

Effects of Gravity

Colloidal particles are much larger than atoms and the bonds between them are

relatively weak. For these reasons gravity can play a prominent role in affecting the

structure and formation of colloidal crystals (Zhu et. al., 1997). The force of gravity can

influence the way colloids interact and lead to colloidal crystallization. For example,

gravity causes sedimentation to occur. This is when the colloid particles settle towards

the bottom of the sample cell and because of the increasing density (the lower boundary

wall triggers layering in the liquid), crystallization and crystal growth can take place. The

results of this are pictured in Figure 9.

(9)

Figure 9: Sedimentation of colloidal particles at the bottom of the container due to gravity

In the sedimentation process in a strong gravitational field, a liquid layer will

originate at the bottom before a crystal. These first two layers of this liquid layer will

Wagenborg 12

“undergo a first order transition with increased gravitational strength” (Hoogenboom et.

al., 2003, 3372). When the sediment has a high Peclet number (the ratio between the

gravitational force and the thermal energy) it resembles a 2-D system and a monolayer of

crystals is formed because the Brownian motion is small. When the Peclet number is low,

the crystals grow epitaxially. The relationship between the sediment and the crystals

formed within the sediment can lead to a determination of whether crystalline sediment

or amorphous sediment will be produced (Hoogenboom et. al., 2003). Gravity has also

been found to accelerate aging in ‘glassy’ systems. This reduces both the time in which

crystal nucleation can take place and the glass transition density Simeonova & Kegal,

2004).

Microgravity

Scientists use the term microgravity to mean very little gravity. “Micro” is a

prefix used in science to mean one millionth and in the space shuttle gravity is reduced by

a factor of 1/1,000,000 that we feel on Earth. On Earth, the acceleration of an object that

is falling to the ground (due to gravity alone) is described as having normal gravity or 1 g

(Zona, 2006). This rate of acceleration is 9.8 m/s 2 .

Sir Isaac Newton first studied these phenomena nearly three hundred years ago

with his ‘falling apple’ dilemma. His work led to Newton’s Law of Universal

Gravitation, which is an understanding that gravity exists between any two objects in the

universe that have mass. The strength of this gravitational force was affected by the mass

of the objects and the distance between them, i.e. F ∝

m m

r

1 2

2 , where F is the gravitational

force between the objects, m stands for mass and r is the distance between the centers of

the two objects. This formula shows that as the distance of the objects increases, the force

between them decreases, but it will never reach zero (Walls, 1997).

Many people mistakenly think that there is no gravity outside the Earth’s

atmosphere, and this is the reason given for why astronauts float onboard the shuttle. The

shuttle and its passengers are acted on by the Earth’s gravitational force (and to some

extent the moon), which helps explain why the ship continues to orbit the planet. The

space shuttle (and other space crafts), however, is about 500 km away from the surface of

the Earth. According to the Law of Universal Gravitation, this increased distance away

Wagenborg 13

from the surface of the Earth will reduce the gravity enormously on the space shuttle (i.e.

to microgravity levels) (Walls, 1997).

Colloidal Experiments in Microgravity

According to NASA, microgravity is the newest science because it was created

with the dawn of the space age. The first microgravity experiments were done almost

forty years ago, the space shuttle has been performing tests for the last thirty years and

the International Space Station has just begun to do the same. Space, because of its small

amount of gravity, is an ideal setting to carry out experiments that could not be performed

anywhere else. In principle, microgravity can be recreated on Earth (NASA’s C-9 low g

flight research aircraft and other zero gravity facilities) but the length of time of this

microgravity is too short for the purposes of the research on equilibrium phenomena.

Objects behave differently in this setting and colloids are no exception (Horack, 1997).

In the 1990’s Paul Chaikin and William Russel, then at Princeton University, set

out to learn how colloidal materials reach a state of equilibrium in microgravity. Their

hope was to be able to eventually influence the process and create objects with

controllable properties. Colloidal suspensions on Earth provide an insight into atomic

structures, but gravity restricts more thorough insights. Weight causes the crystals to

settle at the bottom of the container. This creates more of a concentration at the bottom

than at the top and makes it impossible to observe the sample in equilibrium. They

determined that microgravity would prevent the sedimentation from occurring and also

stop convection (swirling) of the fluid that was a result of the movement of the hard

spheres (Freeman-Hathaway, 2002).

In October 1995, Chaikin and Russel sent their first experiments into space

onboard STS-73. Labeled the Colloidal Disorder-Order Transition (CDOT), the objective

was to see what effect microgravity would have on the crystals in equilibrium (Freeman-

Hathaway, 2002). This mission produced many different results.

First, the crystals grown in microgravity showed the random stacking of

hexagonally close-packed planes (r.h.c.p.) only. On Earth, the crystals showed a

combination of r.h.c.p. and face centered cubic (f.c.c.) packing when given time to settle.

This led to a theory that gravity induced stress may be responsible for the f.c.c. packing.

Wagenborg 14

Next, the crystals in space displayed dendrite growth (Figure 10). Dendrites are fragile

snow-flake like structures that form around the crystal. They sometimes occur in metal

alloys (atomic systems) and are very important in technology (Cheng et. al, 2002). It was

theorized that this growth is part of the normal process, but on Earth the stress of gravity

causes them to shear off as they settle on crystals. On Earth as a crystal grows its mass

causes it to sink quickly. When the viscous stress of the fluid becomes greater than the

stress that the crystal can withstand, the crystal breaks. Hence the dendrites are sheered

off. Lastly, samples that had high volume content fractions on Earth failed to crystallize

completely and looked instead like a glassy substance even after a full year. In

microgravity these same samples crystallized within two weeks (Figure 11). This led the

researchers to conclude that gravity “masks or alters” parts of the crystallization process

(Zhu et. al., 1997, 885). When the shuttle re-entered the earth’s atmosphere and landed,

most of the crystals were destroyed due to their fragile state, but those glass samples that

crystallized in space survived the landing due to the fact that they were already at high

concentration s (Freeman-Hathaway, 2002).

(10) (11)

Figure 10: Left: CDOT results: dendritic colloidal crystal growth, not seen on the Earth.

Figure 11: Crystallization of high volume content samples that were ‘glassy’ and failed to crystallize on

Earth.

The CDOT project was a good start but clearer images were needed from the hard

sphere crystals. Chaikin and Russel set about to develop a device that would show the

Wagenborg 15

structure of the crystals and the creation (nucleation) and growth of crystals. Their

objective was to find out how elastic they were at nucleation and how long it took to

grow (Freeman-Hathaway, 2002). This next phase was known as the Physics of Hard

Spheres Experiment. It was a “series of light scattering experiments on colloids”

conducted on STS-83 and STS-94 (Cheng, et.al.2001, 4146).

These experiments produced more information regarding colloidal crystallization.

Contrary to what was theorized in CDOT, the f.c.c. structure was determined to be the

equilibrium-stable structure for hard sphere crystals. In all of the samples (liquid/crystals,

crystals, glass crystals) the researchers observed the growth of the f.c.c. structure and saw

it sooner when the volume content fraction was increased (Cheng, et.al.2001).

Larger crystals, but smaller in number, (compared to those on Earth) were found

to have grown (See Figure 12). The PHaSE experiments also brought to light that the

competition process of larger crystal growth happens earlier than expected. It was

discovered that nucleation takes place at a variety of locations in the fluid. Some crystals

begin to grow before others; hence some are large when others are just starting. These

larger crystals will eat away at the smaller crystals until there is on large crystal.

Colloidal suspensions are not the only area where this takes place. Another example is

found by breathing on glass. When someone breathes on glass, the vapor condenses into

water droplets and the larger ones grow into one large droplet. This process is known as

simultaneous coarsening and growth (Cheng et. al, 2002, 015501-3). This again showed

how gravity changes the nature of crystallization in their growth and coarsening

processes. On Earth sedimentation will not only limit the growth of the crystals but also

affect the future interactions of the crystals that are moved in the liquid through diffusion

(Cheng et. al., 2001).

(12)

Figure 12: PHaSE results: Larger colloidal crystals grew with the f.c.c. structure

Wagenborg 16

Research then shifted to the International Space Station’s Destiny Lab. This lab,

initialized in 2001, contains a pressured space platform that allows for long term

exposure to microgravity. The Physics of Colloids in Space (PCS), headed by Professor

David Weitz, took place from June 2001 through February 2002. The focus was on:

binary colloidal crystal alloys (suspensions of particles of two different sizes), colloid-

polymer mixtures, where a “mono-disperse particle mixed with a mono-disperse polymer

in an index-matching fluid where the phase behavior is controlled by the concentration of

the colloid, the concentration of the polymer and the relative size of the colloid and the

polymer” (Pellis & North, 2004,595), and fractal gels (colloids with repeating structural

patterns and networks) (Doherty&Sankaran,2002).The binary colloidal crystal produce a

power law growth (still under investigation), and showed more peaks in the powder

pattern than had been seen on Earth This showed gravity’s affect on the size and

morphology of the crystals and gels (See Figure 13). The colloid-polymer samples

produced samples showing two regions: one colloid rich, one colloid poor (spinodal

decomposition). The fractal gels grew crystals much larger than those on Earth, as gravity

would have caused them to be crushed (Doherty & Sankaran, 2002) (Weitz, 2002).

(13)

Figure 13: PCS results: binary colloidal crystal growth in microgravity

Wagenborg 17

Future Experiments and Research

Future colloidal research in microgravity will revolve around the use of the Light

Microscopy Module (LMM). This device will allow fluid and biology experiments within

the Fluids and Combustion Facility (FCF) Fluids Integration Rack (FIR) on the ISS. The

three experiments that will utilize the LMM will be The Physics of Hard Spheres-2

(Chaikin), The Physics of Colloids in Space-2 (Weitz) and The Low Volume Fraction

Entropically Driven Colloidal Assembly (Dr. Arjun Yodh of the University of

Pennsylvania). These experiments will focus on the “nucleation, growth, structure and

properties of colloidal crystals in microgravity and the effects of micromanipulation upon

their properties” (Motil & Snead, 2002, 5). The confocal microscopy piece of the LMM

will allow these three experiments to observe the interior of the colloidal structures,

which would result in three dimensional models (Motil & Snead, 2002)

The PHaSE-2 ‘s goals are to “observe the effects of hard spheres parametric

conditions on the equilibrium phase diagram and how colloidal systems respond to

applied fields” (Motil & Snead,2002,6). The LMM will give the researchers the ability to

observe the position of the particles and allow them to make determinations regarding the

behavior of these particles. The microscope will be accompanied by a set of laser

tweezers. These tweezers, which are composed of tightly beams of laser light, will allow

the researchers to draw the particles into the light beam. The particles would be grabbed

and brought together with the intention of building nuclei. The scientists would have

control over the formation of the crystals. They would be able to see the growth process

step by step in order to see the reasons certain crystals form and how they could

manipulate the crystals to grow in various states (i.e. non equilibrium) (Freeman-

Hathaway,2002).

The goals of the PCS-2 are to “carry out further investigation of critical,

fundamental problems in colloid science and to create materials with novel properties

using colloidal properties as precursors” (Motil & Snead, 2002, 7). These experiments

will use binary alloys and mixtures of colloidal particles with polymers. The polymers are

meant to create a controllable force of attraction, i.e. the depletion attraction between the

colloidal particles. This force will stimulate the creation of new structures and initiate

phases in the suspension. All of this will be measured using the LMM. The objects will

Wagenborg 18

be able to be viewed in real space and the tweezers will be used to manipulate the

structures (Motil & Snead, 2002, 7).

The goals of the Low Volume Fraction Entropically Driven Assembly Experiment

are to “create new colloidal crystalline materials, study the assembly of these materials,

measure their optical properties, and then solidify the resulting structures so they can be

brought back and studied on Earth” (Motil & Snead,2002,7). The samples that will be

used in this experiment include colloidal particles suspended in water and other organic

fluids. The LMM will be used to observe the growth of the crystals. After the images are

acquired they will be stored in order to determine crystal structure and quality.

Sedimentation makes it impossible for these structures to be created on Earth. If the

structures are able to survive re-entry and landing, their optical, magnetic and electrical

properties will be studied more extensively (Motil & Snead, 2002).

Possible Applications of These Experiments

Colloidal Crystallization in microgravity research could impact our world in a

variety of ways. Photonic materials such as ultra low-noise light sources, switches and

computers using light instead of electricity could be produced (Motil & Snead, 2002).

The manipulation of the particles could lead to structures with precise spacing that would

improve the control of light, necessary for better long distance telephone communications

(Freeman-Hathaway, 2002). Knowledge gained also could lead to better ways to use

carbon dioxide for food extractions, more efficient prescription drug processing, and

creating stronger ceramics or even better dry cleaning (Pellis & North, 2004).

Acknowledgement: I would like to thank Dr. Arjun Yodh, the James M. Skinner

Professor of Science at the University of Pennsylvania, for his expertise, his guidance and

most of all his time, which allowed me to complete this content section of my capstone

project.

Wagenborg 19

References

Antonietti, M. (2008). What are colloids? Max Planck Institute of Colloids and

Interfaces. Retrieved from: http://www.mpikg-golm.mpg.de/kc/

Bostrum, M., William, D.R.M. & Ninham, B.W. (2001). Specific ion effects: Why

DLVO theory fails for biological and colloidal systems. Physical Review

Letters. 87(16),168103-1 – 168103-4.

Bowen, W.R. & Sharif, A.O. (1998). Long-range electrostatic attraction between like-

charged spheres in a charged pore. Nature. 393, 663-665.

Cheng, Z., Chaikin, P.M., Zhu, J., Russel, W.B., Meyer, W.V. (2002). Crystallization

kinetics of hard spheres in microgravity in the coexistence regime: interactions

between growing crystallites. Physical Review Letters. 88(1), 015501/1-4.

Cheng, Z., Zhu, J., Russel, W.B.; Meyer, W.V., Chaikin, P.M. (2001). Colloidal hard-

sphere crystallization kinetics in microgravity and normal gravity.

Applied Optics. 40(24), 4146-51.

Cheng, Z. Chaikin, P.M., Russel, W.B., Meyer, W.V., Rogers, R.B., Ottewill, R.H.

(2001). Phase diagram of hard spheres. Materials & Design. 22(7), 529-34.

Doherty, M.P. & Sankaran, S. (2002). Physics of colloids in space: Microgravity

experiment completed operations on the international space station. National

Center For Microgravity Research. Glenn Research Center. Clevland, Ohio.

Einstein, A. (1905). Investigations on the theory of the Brownian movement. Dover

Publications, Inc.

Eldridge, M.D., Madden, P.A., Frenkel, D. (1993).

Entropy-driven formation of a superlattice in a hard-sphere binary mixture.

Nature. 365(6441), 35-7.

Freeman-Hathaway, J. (2002). Building momentum for colloidal engineering. NASA

Research: The Office of Biological and Physical Research. Retrieved from:

http://spaceresearch.nasa.gov/general_info/physicalsciences_06-2002_lite.html

Frenkel, D. (1999). Entropy-driven phase transitions

Physica A. 263(1-4), 26-38.

Frenkel, D. (2006). Plenty of room at the top [colloidal crystals].

Nature Materials. 5(2), 85-6.

Hiemnz, P.C. & Rajagopalan, R. (1997). Principles of Colloid and Surface Chemistry.

New York: Marcel Dekker.

Wagenborg 20

Holt, Rinhart & Winston. (2004). Introduction Into Matter. Austin, Texas: Harcourt

Education Company.

Hoogenboom, J.P., Vergeer, P & van Blaaderen, A. (2003). A real space analysis of

colloidal crystallization in a gravitational field at a flat bottom wall. Journal of

Chemical Physics. 119(6), 3371-3383.

Horack, J. (1997). Microgravity science overview. NASA’s Marshall Space Flight

Center. Retrieved from:

http://science.nasa.gov/MSL1/themes/micrograv_over.htm

Lekkerkerker, H.N.W. & Stroobants, A. (1998). Ordering entropy. Nature.393, 305-307.

Lin, K, Crocker, J.C., Prasad, V., Schofield, A., Weitz, D.A., Lubensky, T.C., Yodh,

A.G. (2000). Entropically driven colloidal crystallization on patterned surfaces.

Physical Review Letters. 85(8), 1770-1773.

Motil, S.M. & Snead, J.H. (2002). The light microscopy module: An orbit multi-user

microscope facility. The International Space Station Utilization-2001.

Cape Canaveral, Florida. October 15-18, 2001.

Van Blaaderen, A. Ruel, R., Wiltzius, P. (1997). Template-directed colloidal

crystallization. Nature. 385(23), 321-324.

Pellis, N.R., North, R.M. (2004). Recent accomplishments onboard ISS. ACTA

Astronautica. 55(3-9), 589-598.

Pusey, P.N. & van Megen, W. (1986). Phase behavior of concentrated suspensions of

nearly hard colloidal spheres. Nature. 320, 340-342.

Russel, W. B., Saville, D. A. & Schowalter, W. R. (1989). Colloidal Dispersions.

Cambridge, England: Cambridge University Press.

Simenova, N.B. & Kegel, W.K. (2004). Gravity induced aging in glasses of colloidal

hard sphere. Physical Review Letter.16.93 (3).

Van Blaaderen & R., Wiltzius, P. (1997). Growing large oriented colloidal crystals.

Advanced Matter. 9(10), 833-835.

Velev, O.D., Lenhoff, A.M. & Kaler, E.W. (2000). A class of microstructured particles

through colloidal crystralization. Science. 287, 2240-2243.

Wagenborg 21

Walls, B. (1997). Free fall and microgravity.

Adapted from NASA's "A Teacher’s Guide With Activities", produced by the

Microgravity Science and Applications Division, Office of Space Science

and Applications, and NASA's Education Division, Office of Human Resources

and Education. Retrieved from:

http://science.nasa.gov/MSL1/ground_lab/msl1freefall.htm

Weitz, D. (2002). Results from the physics collods experiment on iss. The

53rd

International Astronautical Congress. Houston, Texas. October 10-19, 2002.

Yodh, A.G. (2007). Entropic forces: an undergraduate lecture on entropy effects in

solutions (PDF document). Retrieved from:

http://www.physics.upenn.edu/yodhlab/docs/yodh_Phys295Entropic_Forces.pdft

Yodh, A.G. (2006). Condensed matter physics (HTML document). Retrieved from:

http://www.physics.upenn.edu/yodhlab/research_CMP.html

Zhu , J., Li, M., Rogers, R., Meyer, W., Ottewill, R.H., Russel, W.B., Chaikin, P.M.

(1997). Crystallization of hard-sphere colloids in microgravity

Nature. 387(6636) 883-5.

Zona, K. (2006). What is microgravity? Glenn Research Center.Retrieved from:

http://www.nasa.gov/lb/centers/glenn/research/microgex.html

Wagenborg 22

Figure Sources

(1)

Colloidal Nanostructure Group. http://yigira.mireene.com/index_files/ani_colloids.gif

(2)

Complex Fluids/Nonlinear Dynamics Laboratory: Magnetic Probes in Colloidal

Glasses

http://www.physics.emory.edu/~weeks/lab/labpics/threebd.gif

(3)

Zeta Corporation

http://www.zetacorp.com/fig1.gif

(4)

Experimental Soft Condensed Matter Group

http://www.seas.harvard.edu/projects/weitzlab/hsphasediagram.gif

(5)

Nature Publishing Group

www.nature.com

(6-8)

Dr. Arjun Yodh, University of Pennsylvania

http://www.physics.upenn.edu/yodhlab/education.html

(9)

Jeroen van Duijneveldt's research group

http://www.chm.bris.ac.uk/pt/jeroen/pic/SepioliteLC.jpg

(10-12 & Cover)

NASA Space research: The Office of Biological and Physical

Research

http://spaceresearch.nasa.gov/research_projects/images/

physicalsciences_06- 2002_2.jpg

(13)

Physics of Colloids in Space (PCS): Microgravity Experiment Completed

Operations on the International Space Station

www.grc.nasa.gov/.../images/6728doherty-f2.jpg

Wagenborg 23


Pedagogy

Unit Description

The affects of gravity can cause problems for scientists investigating the true

nature of materials and objects on Earth. Scientists have recently started to

perform experiments in microgravity. These classroom activities will enable

middle school students to experiment with the forces and processes microgravity

scientists are investigating today. This unit takes middle school students on a

journey from what microgravity is, to how objects orbit the Earth and exist in

microgravity, and finally to demonstrations and activities on how gravity affects

atom arrangement, solidification and growth of crystals. The activities employ

simple and inexpensive materials and apparatus that are widely available in

schools. The activities emphasize hands-on involvement, prediction, data

collection and interpretation, group work and problem solving.

Unit Enduring Understanding

Students Understand:

1. The amount of gravity between two objects depends upon various conditions

and forces in the universe.

2. The presence or absence of gravity affects the behavior, structure and function

of materials that it acts upon.

3. Creating and investigating scientific models allows us to observe phenomena

that are impossible to completely recreate on Earth.

Unit Essential Questions

• How is an environment of microgravity created?

• How are spacecrafts affected by various forces in space?

• How does gravity limit the amount of scientific knowledge we can gain on Earth

about certain materials?

Wagenborg 24

• How do space experiments open up new areas of information that will better our

lives?

What Students Will Need to Know

By the end of this unit students will be able to:

• explain how an environment of microgravity is created.

• explain how a spacecraft orbits the Earth and the conditions of that orbit.

• describe how gravity affects materials on Earth; specifically the atom

arrangement, sedimentation and growth of crystals.

• explain the reasons for why scientists experiment in microgravity.

• analyze a scientific article and communicate its relevance to their lives.

Student Misconception

Middle school students bring many misconceptions with them to a unit on

microgravity. These misconceptions regarding orbit, gravity, mass and weight, atoms and

crystals could be detrimental to a complete understanding of the concepts in this unit, if

they are not recognized.

When students explain how and why objects stay in orbit around the Earth, their

answers usually revolve around two central ideas. The first is that the rockets of a

spacecraft cause it to fly around the Earth. The second is that there is no gravity in space,

because it only exists on Earth (NASA, 2007).

Speaking of gravity, students make many errors in their thinking. They assume

that if an object is not moving, there is no force acting on it. They believe that an object

that is on the ground is not acted on by gravity because it has already fallen to the ground.

Thus they see objects that are falling as having more gravity than stationary objects

(Thagard, 1992; Vosniadou, 1994). Students also think of gravity as the result of air

pressure and a property of the object itself (Prescott, 2004).

Students fail to recognize the difference between mass and weight. They link

them together probably because they are the same value on Earth due to gravity. This

leads them to failure in understanding the changes that occur to objects in space

(Amazing Space, 2006).

In terms of atoms, students do not realize that they are the matter; rather they

concentrate on how atoms fill up the matter. Students in middle school also have

problems conceptualizing that atoms are in constant motion (AAAS, 1993).

Wagenborg 25

Students bring many preconceived notions when comes to crystals, thus they do not

see them on the scientific level. They often visualize them as manmade, shiny and found

in caves. Students do not associate the words liquid, atoms or order when thinking about

crystals. They do not see that crystals are an organization of the atoms of a material (Dal,

2007).

National Science Education Standards:

Science as Inquiry:

• Abilities necessary to do scientific inquiry

• Understandings about scientific inquiry

Physical Science:

• Properties and changes of properties in matter

• Motions and forces

Earth and Space Science

• Structure of the Earth’s system

Change in Personal and Social Perspectives

• Science and technology in society

Pennsylvania Standards

3.2. Inquiry and Design

A. Explain and apply scientific and technological

knowledge.

B. Apply process knowledge to make and interpret

observations

C. Identify and use the elements of scientific inquiry to

solve problems

D. Know and use the technological design process to

solve problems

3.4 Physical Science, Chemistry and Physics

A. Describe concepts about the structure and properties of

matter.

B. Describe essential ideas about the composition and

structure of the universe and the earth’s place in it.

Wagenborg 26

3.6. Technology Education

C. Explain physical technologies of structural design,

analysis and engineering, personnel relations, financial

affairs, structural production, marketing, research and

design.

Preconceptions Assessments

Concept Map

Students will make a concept map using the following words:

force, free fall, gravity, mass, microgravity, motion, orbit, weight,

weightlessness, atoms and crystals

I will be assessing:

- what their pre knowledge is of these words (vocabulary)

- what assumptions they make about how the word/concepts are

connected

I want to know how well they understand the words we will be using, if

they are using them incorrectly and how far a long their thought process is

for how they are connect with one another.

Pre Class Questions

(Given before each of the lessons through discussion or written response.

This will depend on the make up of the class)

1. Why do astronauts float in space?

2. How does the space shuttle or a satellite orbit the Earth?

3. What determines the form and function of an object?

4. How do you think gravity affects our life on Earth? Give an example.

5. Why do Astronauts conduct experiments in space?

Performance Assessment (Based on Ohio, 2008)

Goal:

The overall goal is to see that the students can demonstrate an

understanding of:

Wagenborg 27

- how gravity affects materials on Earth

- the reasons for why scientists experiment in microgravity

Role:

You are microgravity scientists who have been contacted by NASA. In the future

NASA will start sending the families of Astronauts to the International Space

Station so the Astronauts can spend more time up there working. This means that

there will be children onboard trying to stay entertained in a microgravity

environment. NASA wants you to observe and experiment with different toys and

your research will be used by them to select the best toys that will keep the

children happy. Remember there is nothing worse then a bored child stuck in

space.

Audience:

NASA’s Future Missions Division (Your classmates)

Situation:

Students will be given these instructions:

You are to imagine that you are a microgravity scientist investigating the effects

of gravity on the motion of certain toys. You are to choose for investigation three

toys that have motion. Using a graphic organizer, you will record your

observations that will detail how gravity causes them to move the way that they

do. You will then use this information to hypothesize how the motion would

change if it took place in a microgravity environment on the space shuttle or the

International Space Station. Once your observations and hypotheses are complete,

you will create either a power point slide show or a three-sided board to present

your findings to your fellow scientists (the class).

Product:

A graphic organizer and a power point slide show or a three-side presentation

board.

Standards:

A. Required Elements

1. All graphic organizers must include:

A detailed list of three toys that have motion

A written explanation of gravity’s observed affects each toy’s

motion

A written hypothesis of the changes that would be brought about

by microgravity on each toy

Wagenborg 28

2. All presentations must include:

Pictures or illustration of the toys used in the investigation

A summary of the motion observed for each toy investigated

A hypothesis and explanation for each toy’s motion in a

microgravity environment

A drawing or diagram of the toy’s new motion in microgravity

B. Sequence: The observations of the toys’ motions must be done before making

hypotheses about a microgravity environment.

C. Writing Mechanics: Your observations and hypotheses must be clearly written

and contain and detailed explanations. There must be no

grammatical or punctual errors.

D. Creative Elements: Your hypotheses should be creative and your

PowerPoint/three-sided board should be visually appealing

to your classmates.

E. Use of Class Time and Cooperation: Although you will perform your

observations at home, you will be given computer time

during tech period to work on your power point or three-

sided board. I will be available before and after school

for assistance.

*** Students who are in need will be provided with toys, computer use or a three-sided

board that will allow them to complete the assessment.

Other Assessments

•••• Discussions before each lesson will serve as a review for the

previous lesson. I will assess their understanding not their

ability to memorize.

•••• Observation/Data sheets for each lesson. I will assess their

understanding of each lab through their written words and drawings on each sheet.

Wagenborg 29

•••• Post Assessment Concept Map-using the same words from the

pre assessment. I will assess how their understandings have

grown by comparing the two maps.

•••• Quiz – multiple choice, true/false and short answer

questions. This will assess their ability to demonstrate the

enduring understandings, essential questions and objectives of

this unit

*Hook*

Attention Graber (Unit Opening Demonstration)

“Falling Water”

(Holt, 2004)

Purpose: To get the students interested and thinking about gravity

and its affects on analyzing objects.

Materials: Styrofoam cup, bucket, a pencil and tap water

Procedure:

1. Show the cup to the students and ask them to hypothesize what will happen

if you filled the cup with water and then poked a hole in the bottom. Have

them write the hypothesis (with a reason) in words and draw a picture.

2. Have students share their thoughts.

3. Poke a hole in the bottom of the cup with a pencil, hold your finger over

the hole and pour in the water to fill the cup.

4. Release your finger and have the students write down their observations.

(the water should flow almost straight down)

5. Ask the students what they would see if you dropped the cup at the exact

same time that you released your finger. Have them write down their

hypotheses and then share out.

Wagenborg 30

6. Perform the act (the water will not be seen falling out of the cup).

7. Listen to students’ responses for why. Explain to them that gravity played a

part in both examples and that they will learn how in this unit.

* The students should keep their hypotheses in their notebooks because they will revisit

their responses towards the end of the unit. This will serve the role of a pre test.

Differentiated Instructional Support For The Unit:

Instruction is differentiated according to learner needs. This applies to those who need

help meeting the objectives or those who exceed them.

• Students who have difficulty writing may verbally present how different things

react in microgravity and give oral explanations about what is happening.

• Students will be placed in groups based on their academic ability. The groups will

be heterogeneous to provide support for all students.

• In some lessons a video camera will be used to videotape the experiment (not the

students). The video cameras allow, the replay of the experiment. This replay can

be done frame-by-frame to allow students to see what is happening.

• Those students who need to be challenged may work on the extension activities

listed after the lesson.

Lessons

*All days are based on a forty-five minute period

*Where and Hook* Day 1 This will be the introductory and pre-assessment day. First I will perform the attention

grabber activity (described above) to get them interested and curious about the entire unit.

(hook). Next I will have students create their concept maps (described above). Finally, I

will have a discussion to prepare them and get their thoughts about what will take place

the next two weeks. This includes discussions about topics, activities and assignments.

(where). At the start of each class students will answer a pre-class question that we serve

as an indication of where the lesson is headed that day, a hook to get them excited and

curious about what we are doing that day and a pre-assessment to let me know about their

knowledge and misconceptions on that particular topic.

*Reflect* Each night for homework (in addition to other assignments given) the students will

reflect on the day’s activities. They will focus on what they learned, how they felt and

how they think it applies to their world. The next day we will review these assignments.

This will allow me to guide them in building a more complete understanding as they

perform each activity.

Wagenborg 31

*Engage* Day 2 Activity: Microgravity in the Classroom-Can Throw (NASA, 2007)

E.U.: The amount of gravity between two objects depends upon various conditions and

forces in the universe.

E.U.: Creating and investigating scientific models allows us to observe phenomena that

are impossible to completely recreate on Earth.

Objective: To demonstrate how microgravity is created by freefall

The purpose of this activity is for students to create a microgravity environment

for a can using freefall using a soda can and water. After answering a pre-class question,

the students will work in groups observing the water flow from the can during different

stages of motion. The goal is for the students to see how gravity is reduced during

freefall, which can be compared to how microgravity is created in space. Students will

write down all of their observations and we will have a wrap up discussion during the last

part of class.

Day 3 Activity: Around The World (NASA, 2007)

E.U.: The amount of gravity between two objects depends upon various conditions and

forces in the universe.



Objective: To create a model of how satellites orbit the Earth.

The purpose of this activity is for students to use experimentation to discover the

conditions needed for a small ball on a string to go around a larger ball. Students will

work in groups and discover the angle and speed necessary for this to occur. This will

simulate how a satellite orbits the Earth. A video camera will be used to record the

attempts (focused only on the experiment not the students). The students will complete

data sheets that will be collected and we will have a wrap up discussion during the last

part of class.

Day 4 Activity: Crystallization Model (NASA, 2007)

E.U.: The presence or absence of gravity affects the behavior, structure and function of

materials that it acts upon.



Objective: To demonstrate how atoms in a solid arrange themselves.

The purpose of this activity is for the students to be able to observe and then explain how

gravity influences the positioning of atoms in a solid. BBs will be placed on a platform

and will be subjected to different speeds. The BBs will represent the atoms, the platform

Wagenborg 32

will represent the Earth environment and the speeds resemble temperature. This activity

is a teacher demonstration given to one small group at a time. Students will first answer a

pre-class question and then list and draw predictions for what they think will occur to the

BBs at different speeds. The students will record all of their data on sheets that will be

collected. We will have a discussion about what was observed and discuss how these

events would be different in a microgravity environment.

Days 5 and 6 Activity: Microscopic Observation of Crystal Growth

E.U.: The presence or absence of gravity affects the behavior, structure and function of

materials that it acts upon.



Objective: To explain crystal nucleation and growth rate during solidification.

The purpose of this activity is for the students to observe and then be able to describe

how a crystal forms when influenced by gravity. The students will answer a pre-class

question and then observe two white powders, mennite and salol. They will make and

draw predictions for what they think the powders would look like during phase changes.

On each of the two days, the students will melt a powder; expose it to colder

temperatures and then watch under a microscope as it re-crystallizes. Only one of the

powders will be experimented with each day. Students will work in small groups and

complete their data sheets, which will be collected. At the end of each day we will

reconvene and discuss what was observed and if what they saw would be different in a

microgravity environment.

Days 7- 8

“Zeolite Crystal Growth”

(NASA, 2007)

Purpose: This lesson will allow students to grow zeolite crystals and see what effect

gravity has on their growth. The goal is for students to further deepen their

understandings of the effects of gravity of objects and to develop an understanding of

why scientists conduct microgravity experiments. Zeolite crystals are used in the

production of gas, as filters in aquariums and in laundry detergents.

Enduring Understandings:

. Gravity-driven phenomena, or lack there of, affect the structure, behavior and

function of materials that the force acts upon.

. Creating and investigating scientific models allows us to observe phenomena

that are impossible to completely recreate on Earth.

Wagenborg 33

Time Frame: The main part of the lesson will take two forty-five minute class periods,

the total lesson requires eight days due to daily observations. This time

table can be reduced if there are time restrictions.

Objective: To grow zeolite crystals and

investigate how gravity affects their growth.

Science Standards: Science as Inquiry,

Physical Science ,Unifying Concepts and

Processes Change, Constancy, & Measurement

Science Process Skills: Observing

Communicating ,Measuring ,Collecting Data,

Controlling Variables, Investigating

MATERIALS AND TOOLS

Sodium aluminate NaAIO 2

FW=81.97

Sodium metasilicate anhydrous, purum,

Na2O3Si, FW=122.06

Sodium hydroxide pellets, 97+%, average

composition

NaOH, FW=40

Triethanolamine (TEA), 98%

(HOHCH2)3N, FW=149.19

Distilled water

1000 ml Pyrex ® glass beaker

Aluminum foil

Metric thermometer with range up to 100C

Laboratory hot plate

2-60 ml high-density polyethylene bottles with

caps

4-30 ml high-density polyethyene bottles with caps

Plastic gloves

Goggles

Glass microscope slides

Permanent marker pen for marking on bottles

Waterproof tape

Lead fishing sinkers

Tongs

Eyedropper

Optical microscope, 400X

Wagenborg 34

Activity Management: The preparation of zeolite crystals, although not difficult, is an

involved process. A number of different chemicals must be carefully weighed and mixed.

You may wish to prepare the chemicals yourself or assign some of your more advanced

students to the task. Refer to the materials and tools list on the next page for a detailed list

of what is required.

This activity involves maintaining a hot water bath continuously for up to 8 days. If you

do not have the facilities to do this, you can conduct the experiment for just the 0 and 1

TEA (triethanolamine) samples described below. Crystals may also be formed if the hot

water bath is turned off at the end of the school day and turned on the succeeding day.

Crystallization times will vary under this circumstance, and close monitoring of the

formation of the crystalline precipitate will be necessary.

Following the growth of zeolite crystals, small samples can be distributed to student

groups for microscopic study.

*Where and Hook*

Student Pre- Class:

Students will answer the following before the lesson begins.

• “Why do Astronauts conduct experiments in space?”

• “We are going to grow zeolite crystals. What do you know about crystals? Draw

what you think the crystals that we will grow will look like.”

Data Collection: Each student will be given two data sheets (see appendix) on which

they will write and draw their observations and record their results.

Wagenborg 35

Procedure:

1.While wearing hand and eye protection, weigh 0.15 grams of

sodium hydroxide and place it in a 60 ml, high-density polyethylene

bottle. Add 60 ml of distilled water to the bottle and cap it. Shake the

bottle vigorously until the solids are completely dissolved. Prepare a

second bottle identical to the first.

2.Add 3.50 grams of sodium metasilicate to one of the bottles and

again cap it and shake it until all the solids are dissolved. Mark this

bottle "silica solution." To the second bottle, add 5.6 grams of

sodium aluminate and cap it and shake it until all the solids are

dissolved. Mark this bottle "alumina solution."

3.Using a permanent marker pen, mark the four, 30 ml high-density

polyethylene bottles with the following identifications: 0 TEA, 1

TEA, 5 TEA, and 10 TEA. 4. Place 0.85 grams of TEA into the

bottle marked "1 TEA." Place 4.27 grams of TEA into the bottle

marked "5 TEA." Place 8.55 grams of TEA into the bottle marked

"10 TEA." Do not place any TEA into the bottle marked "0 TEA."

4.Add 10 ml of the alumina solution to each of the bottles. Also add

10 ml of the silica solution to each bottle.

5.Cap each bottle tightly and shake vigorously. Secure each cap with

waterproof tape and tape a lead sinker to the bottom of each bottle.

The sinker should weigh down the bottle so it will be fully immersed

in the hot water.

6.Prepare a hot water bath by placing approximately 800 ml of water

in a 1000 ml Pyrexs beaker. Place the four weighted bottles into the

beaker. The water should cover the bottles. Cover the beaker with

aluminum foil and punch a small hole in the foil to permit a metric

thermometer to be inserted. Fix the thermometer in such a way as to

prevent it from touching the bottom of the beaker. Place the beaker

on a hot plate and heat it to between 85 and 95 C. It will be

necessary to maintain this temperature throughout the experiment.

Although the aluminum foil will reduce evaporation, it will be

necessary to periodically add hot (85 to 90 C) water to the beaker to

keep the bottles covered.

7.After 1 day of heating, remove the bottle marked 0 TEA from the

bath with a pair of tongs. Using an eyedropper, take a small sample

of the white precipitate found on the bottom of the bottle. Place the

sample on a glass microscope slide and examine for the presence of

crystals under various magnifications. Make sketches or photograph

Wagenborg 36

any crystals found. Be sure to identify magnification of the sketches

or photographs and estimate the actual sizes of the crystals.

Determine the geometric form of the crystals. Look for crystals that

have grown together.

8.Repeat procedure 8 for the 1 TEA bottle after 2 days of heating.

Repeat the procedure again for the 5 TEA bottle after 5 days and for

the 10 TEA bottles after 8 days. Compare the size, shape, and

intergrowth of the crystals formed in each of the bottles.

Homework:

Students will be given an article from the ESA (see link below) on the interests and

findings of Microgravity Research. They will select one of the five interests and one of

the four discoveries to summarize. In their summaries they must include how it affects

them directly.

http://www.spaceflight.esa.int/file.cfm?filename=mgprogsexpts

Lesson Assessment:

Students’ sketches and written descriptions of the zeolite crystals, and informal teacher

observations will be used to judge their level of understanding.

Extension:

Obtain zeolite filter granules from a pet shop. The granules are used for filtering

ammonia from aquarium water. Set up a funnel with filter paper and fill it with the

granules. Slowly pour a solution of water and household ammonia (ammonia without

lemon or other masking scents) into the granules. Collect the liquid below and compare

the odor of the filtered solution and the unfiltered solution. Try running the filtered

solution through a second time and again compare the odors. Be sure to wear eye

protection.

Wagenborg 37

Background Information For The Teacher

Zeolites

Zeolites are crystals made up of the elements silicon,

aluminum, and oxygen. The crystals consist of

alternating arrays of silica (beach sand, SiO2) and

alumina (aluminum oxide, Al203) and can take on many

geometric forms such as cubes and tetrahedra.

Internally, zeolites are rigid sponge-like structures with

uniform but very small openings (e.g., 0.1 to 1.2

nanometers or 0.1 to 1.2 X 10-9

meters). Because of this

property, these inorganic crystals are sometimes called

"molecular sieves." For this reason, zeolites are

employed in a variety of chemical processes. They

allow only molecules of certain sizes to enter their

pores while keeping molecules of larger sizes out. In a

sense, zeolite crystals act like a spaghetti strainer that

permits hot water to pass through while holding back

the spaghetti. As a result of this filtering action, zeolites

enable chemists to manipulate molecules and process

them individually.

The many chemical applications for zeolite crystals

make them some of the most useful inorganic materials

in the world. They are used as catalysts in a large

number of chemical reactions. (A catalyst is a material

that has a pronounced effect on the speed of a chemical

reaction without being affected or consumed by the

reaction.) Scientists use zeolite crystals to produce the

entire world's gasoline though a chemical process

called catalytic cracking. Zeolite crystals are often used

in filtration systems for large municipal aquariums to

remove ammonia from the water. Because they are

environmentally safe, zeolites have been used in

laundry detergents to remove magnesium and calcium

ions. This greatly improves detergent that suds in

mineral-rich "hard" water. Zeolites can also function as

filters for removing low concentrations of heavy metal

ions, such as Hg, Cd, and Pb, or radioactive materials

from wastewaters.

Although scientists have found many beneficial uses for zeolites, they have only an

incomplete understanding of how these crystals nucleate (first form from solution) and

grow (become larger). When zeolites nucleate from a water solution, their density (twice

that of water) causes them to sink to the bottom of the special container (called an

Wagenborg 38

autoclave) they are growing in. This is a process called sedimentation, and it causes the

crystals to fall on top of each other. As these crystals continue to grow after they have

settled, some merge to produce a large number of small, intergrown zeolite crystals

instead of larger, separate crystals.

Zeolite crystal growth research in the microgravity environment of Earth orbit is expected

to yield important information for scientists that may enable them to produce better

zeolite crystals on Earth. In microgravity, sedimentation is significantly reduced and so is

gravity-driven convection. Zeolite crystals grown in microgravity are often of better

quality and larger in size than similar crystals grown in control experiments on Earth.

Exactly how and why this happens is not fully understood by scientists. Zeolite crystal

growth experiments on the Space Shuttle and on the future International Space Station

should provide invaluable data on the nucleation and growth process of zeolites. Such an

understanding may lead to new and more efficient uses of zeolite crystals.

Wagenborg 39

*Exhibit*

Days 9 and 10 and Beyond

During the final days of the unit students will complete a quiz, work on their post unit

concept map, and present their performance assessment (toys with and without gravity).

These tasks will allow students to provide evidence of their understanding through the

exhibition of their work. These are all described above.

Additional Resources

NASA’s Microgravity Lessons. This is a website produced by NASA’s Education

Division. This website contains the five activities that I put into this unit and many others

as well. Activities on microgravity’s affect surface tension; flammability and fluid

dynamics are just some of the examples of activities that could be found.

(http://quest.nasa.gov/space/teachers/microgravity/index.html)

NASA Educator Resource Laboratory. This address and website is the source for all

additional materials, questions or comments that deal with the activities involved in this

unit. This address is for schools in the mid-Atlantic region. The website contains

addresses for additional regions.

NASA Educator Resource Laboratory

Mail Code 130.3

NASA Goddard Space Flight Center

Greenbelt, MD 20771-0001

Phone: (301) 286-8570 http://spacelink.nasa.gov

Educational Videotape. Microgravity- Length 23:24. This video describes how gravity

affects science experiments and the types of experiments done in a microgravity

environment. Experiments include those done on the space shuttle and on the

International Space Station. This tape can be order through NASA’s educators website at:

http://spacelink.nasa.gov

Microgravity Slides - Grades: 8-12 .This set of 24 slides shows the basic concepts of

microgravity. Pictures, demonstrations and diagrams are used to provide students will

visual representations of key ideas. This slide set can be ordered through

Wagenborg 40

NASA On-line Resources for Educators. This provides current educational information

and instructional resource materials to teachers, faculty, and students. This site contains

lesson plans involving different areas of science and mathematics, historical information

and current NASA projects related to student interests. The site also provides links to

other sites for similar topics. The NASA Education Home Page:

http://www.hq.nasa.gov/education

Stephen Hawkins On-Line Microgravity Education and Research Center. This site

contains information for teachers from kindergarten and up, students and parents

involving microgravity. There are pictures of previous space flights, schedules of

upcoming flights and recent media releases about the subject.

http://www.hawkingcenter.org/

SpaceRef Dictionary. This website contains a glossary to important words used with

microgravity and astronomy. It also contains links to NASA’s Office of Life and

Microgravity Sciences and Applications.

http://www.spaceref.com/directory/education/microgravity_sciences/

Gravity and Black Holes-Annotated Resources. This site contains a list of fiction and

non-fictions books and web sites that involve microgravity.

http://www.adlerplanetarium.org/education/resources/gravity/annotated.shtml

Virtual Astronaut. This site provides resources for teachers in all grades. The resources

are in PDF format and include lessons, games, NASA, flight information.

http://virtualastronaut.tietronix.com/teacherportal/EducatorResources.aspx

Discovery Education. This site provides information and resources on the International

Space Station. This includes how humans function and what work is done in space.

http://school.discoveryeducation.com/schooladventures/spacestation/resources.html

Acknowledgements: I would like to thank my pedagogy reader, Amy Dewees, a member of MISEP Cohort 1,

for her guidance during the creation of this unit.

I would also like to thank my wife Nicole, for her love, patience and support during this

whole process.

Wagenborg 41

Appendix

Lesson Procedures

Microgravity in the Classroom

Around the World

Crystallization Model

Microscopic Observation of Crystal Growth

Data Sheets For The Following Lessons

Around the World

Crystallization Model

Microscopic Observation of Crystal Growth

Zeolite Crystal Growth

Performance Assessment Graphic Organizer

Wagenborg 42

“Microgravity In The Classroom: Can Throw”

(NASA, 2007)

Objective: · To demonstrate how microgravity

is created by freefall.

Science Standards:

Science as Inquiry

Physical Science

- position and motion of objects

Change, Constancy, & Measurement

- evidence, models, & exploration

Science Process Skills:

Observing

Communicating

Making Models

Defining Operationally

Investigating

Predicting

Mathematics Standards:

Computation & Estimation

Measurement

MATERIALS AND TOOLS

Empty aluminum soft drink can

Sharp nail

Catch basin

Water

Towels

Television camera, videotape recorder,

and monitor (optional)

Procedure:

1. Punch a small hole with a nail near the bottom of an empty soft drink can.

2. Close the hole with your thumb and fill the can with water.

3. While holding the can over a catch basin, remove your thumb to show that the water

falls out of the can.

4. Close the hole again and stand back about 2 meters from the basin.

5. Toss the can through the air to the basin, being careful not to rotate the can in flight.

6. Observe the can as it falls through the air.

(Optional) Videotape the can toss and play back the toss frame-to-frame to observe the

Wagenborg 43

hole of the can.

Explanation: When the can is stationary, water easily pours out of the small hole and

falls to the catch basin. However, when the can is tossed, gravity's effects on the can and

its contents are greatly reduced. The water remains in the can through the entire fall

including the upward portion. This is the same effect that occurs on aircraft flying in

parabolic arcs.

Wagenborg 44

“Around The World”

(NASA, 2007)

Objective: · To create a model of how satellites

orbit Earth.


Physical Science - position and motion of

object, Change, Constancy, & Measurement -

evidence, models, & exploration

Science Process Skills: Observing,

Communicating, Making Models Defining

Operationally Investigating

MATERIALS AND TOOLS

Large ball*

Small ball

2 meters of string

Flower pot* ,* A world globe can substitute for the large

ball and flower pot

Activity Management: This activity can be conducted as a demonstration or a small

group activity at a learning station where student groups take turns.

Pick a small ball to which it is easy to attach a string. A small slit can be cut into a tennis

ball or racquetball with a sharp knife. Then, a knotted string can be shoved through the

slit. The slit will close around the string. A screw eye can be screwed into a solid rubber

or wood ball and a string attached to it.

If using this as an activity, have students work in groups of two. The large ball and

flowerpot should be placed on the floor in an open area. Tell students to imagine the ball

is Earth with its North Pole straight up. One student will stand near the ball and pot and

hold the end of the string the small ball is attached to. This student's hand should be held

directly over the large ball's north pole, and enough string should be played out so that

the small ball comes to rest where the large ball's equator should be. While the first

student holds the string steadily the second student starts the small ball moving. The

objective is to move the small ball in a direction and at a speed that will permit it to orbit

Wagenborg 45

the big ball. Save the student reader for use after students have tried the activity.

Additional Information: This model of a satellite orbiting around Earth is effective for

teaching some fundamentals of orbital dynamics. Students will discover that the way to

orbit the small ball is to pull it outward a short distance from the large ball and then start

it moving parallel to the large ball's surface. The speed they move it will determine where

the ball ends up. If the small ball moves too slowly, it will arc "down" to Earth's surface.

NASA launches orbital spacecraft in the same way. They are carried above most of

Earth's atmosphere and aimed parallel to Earth's surface at a particular speed. The desired

altitude for the satellite determines the speed. Satellites in low orbits must travel faster

than satellites in higher orbits.

In the model, the small ball and string become a pendulum. If suspended properly, the at-

rest position for the pendulum is at the center of the large ball. When the small ball is

pulled out and released, it swings back to the large ball. Although the real direction of

gravity's pull is down, the ball seems to move only in a horizontal direction. Actually, it

is moving downward as well. A close examination of the pendulum reveals that as it is

being pulled outward, the small ball is also being raised higher off the floor.

The validity of the model breaks down when students try orbiting at different distances

from the large ball without adjusting the length of the string. To make the small ball orbit

at a higher altitude without lengthening the string, the ball has to orbit faster than a ball in

a lower orbit. This is the opposite of what happens with real satellites.

Assessment: Use the student pages for assessment.

Extensions:

Investigate the mathematical equations that govern satellite orbits such as the relationship

between orbital velocity and orbital radius.

Learn about different kinds of satellite orbits (e.g., polar, geostationary, geosynchronous)

and what they are used for.

Look up the gravitational pull for different planets. Would there be any differences in

orbits for a planet with a much greater gravitational pull than Earth's? Less than Earth's?

4. Use the following equation to determine the velocity a satellite must travel to remain in

orbit at a particular altitude:

v = velocity of the satellite in meters GM = gravitational constant times Earth's mass

(3.99x1014

meters 3 /sec

2) r = Earth's radius (6.37x10

6 meters) plus the altitude of the

satellite.

Wagenborg 46

Crystallization Model”

(NASA, 2007)

Objective: · To demonstrate how atoms in a

solid arrange themselves.


Physical Science - position and motion of

objects, Unifying Concepts & Processes

Change, Constancy, & Measurement , Science

& Technology - abilities of technological design

Science Process Skills:

Observing

Communicating

Collecting Data

Inferring

Predicting

Interpreting Data

Hypothesizing

Controlling Variables

Investigating

CONTENTS

MATERIALS AND TOOLS

Wood base and supports

Shallow pan

3 Small bungee cords

Small turnbuckle

Surplus 1 10 volt AC electric motor

Motor shaft collar

Variable power transformer

Several hundred BBs

Hook and loop tape

Activity Management: The crystal model device described here is best suited for use as

a classroom demonstration. It is a vibrating platform that illustrates in two dimensions the

development of crystal structure and defect formation. BBs, representing atoms of one

kind, are placed into a shallow pan, which is vibrated at different speeds. The amount of

vibration at any one time represents the heat energy contained in the atoms. Increasing

the vibration rate simulates heating of a solid material.

Eventually, the atoms begin to separate and move chaotically. This simulates melting.

Reducing the amount of vibration brings the atoms back together where they "bond" with

each other. In this demonstration, gravity pulls the BBs together to simulate chemical

bonds. By observing the movement of BBs, a number of crystal defects can be studied as

they form and transform. Because of movements in the pan, defects can combine

(annihilation) in such a way that the ideal hexagonal structure is achieved and new

defects form.

Wagenborg 47

The model is viewed best with small groups of students standing around the device. After

the solid "melts," diminish the motor speed gradually to see the ways the atoms organize

themselves. It is important that the platform be adjusted so it is slightly out of level. That

way, as the motor speed diminishes the BBs will move to the low side of the pan and

begin organizing themselves. If this does not happen, apply light finger pressure to one

side of the pan to lower it slightly. This will not affect the vibration movements

significantly. While doing the demonstration, also stop the vibration suddenly. This will

simulate what happens when molten material is quenched (cooled rapidly).

The motor collar required in the materials list is available from a hardware store. The

purpose of the collar is to provide an off center weight to the shaft of the motor. The

setscrew in the collar may have to be replaced with a longer one so that it reaches the

motor shaft for proper tightening.

Constructing The Vibrating Platform Note: Specific sizes and part descriptions have

not been provided in the materials list because they will depend upon the dimensions of

the surplus electric motor obtained. The motor should be capable of several hundred

revolutions per minute.

1.Mount three vertical supports on to the wooden base. They can be attached with corner braces or by

some other means.

2.Mount the surplus motor to the bottom of the vibrating platform. The specific mounting technique

will depend upon the motor. Some motors will feature mounting screws. Otherwise, the motor may

have to be mounted with some sort of strap. When mounting, the shaft of the motor should be aligned

parallel to the bottom of the platform.

3.Slip the collar over the shaft of the motor and tighten the mounting screw to the shaft. See the

diagram for how the shaft and collar should look when the collar is attached properly.

4.Suspend the platform from the three vertical supports with elastic shock (bungee) cords or springs.

Add a turnbuckle to one of the cords for length adjustment. Shorten that cord an amount equal to the

length of the turnbuckle so the platform hangs approximately level.

Wagenborg 48

Conducting The Experiment

1.Turn up the voltage on the variable transformer until the BBs are dancing about in the

pan. This represents melting of a solid.

2.Shut the variable transformer off. This represents rapid cooling of the liquid to a glassy

(amorphous) state. Observe and sketch the pattern of the BBs and of the defects.

3.Turn up the voltage again and gradually reduce the vibration until the BBs are moving

slowly. Observe how the BBs move and pack together.

Assessment: Collect the student work sheets.

Extensions:

Obtain some mineral crystal samples and examine them for defects. Most crystals will

have some visible defects. The defects will be at a much larger scale than those illustrated

in the student reader. One defect that is easy to find in the mineral quartz is color

variations due to the presence of impurities.

Investigate the topic of impurities deliberately incorporated in crystals used to

manufacture computer chips. What do these defects do?

Design a crystal-growing experiment that could be used on the International Space

Station. Conduct a ground-based version of that experiment. How would the experiment

apparatus have to be changed to work on the space station?

5.Using hook and loop tape, mount the pan on the upper side of the vibrating platform.

6.Place several hundred BBs in the pan. If the BBs spread out evenly over the pan, lengthen the

turnbuckle slightly so the BBs tend to accumulate along one side of the pan.

7.Turn on the motor by raising the voltage on the variable transformer. If the device is adjusted

properly, the BBs will start dancing in the pan in a representation of melting. Lower the voltage

slowly. The BBs will slow down and begin to arrange themselves in a tight hexagonal pattern. If you

do not observe this effect, adjust the leveling of the platform slightly until you do. It may also be

helpful to adjust the position of the motor slightly.

Wagenborg 49

“Microscopic Observation of Crystal Growth”

(NASA, 2007)

Objective: To observe crystal nucleation and

growth rate during directional solidification.

Science Process Skills: Observing

Communicating ,Investigating

Science Standards:

Science as Inquiry

Physical Science

- position and motion of objects

- properties of objects and materials

Unifying Concepts and Processes

Change, Constancy, & Measurement

MATERIALS AND TOOLS

Bismarck brown Y

Mannite (d-mannitol)

HOCH2(CHOH)4CH20H

Salol (Phenyl salicylate)

C13H10O3

Microprojector

Student microscopes (instead of a micro projector)

Glass microscope slides with cover glass

Ceramic bread-and-butter plate

Refrigerator

Hot plate or desktop coffee cup warmer

Forceps

Dissecting needle

Spatula

Eye protection

Activity Management The mannite part of this activity should be done as a

demonstration, using a micro projector or microscope with a television system. It is

necessary to heat a small quantity of crystalline mannite on a glass slide to 168C and

observe its recrystallization under magnification. The instructions call for melting the

mannite twice and causing it to cool at different rates. It is better to prepare separate

samples so they can be compared to each other. The slide that is cooled slowly can easily

be observed under magnification as crystallizes. You may not have time to observe the

rapidly chilled sample properly before crystallization is complete. The end result,

however, will be quite apparent under magnification. If students will be conducting the

second part of the activity, it is suggested that you prepare several sets of mannite slides

so they may be distributed for individual observations. The salol observations are suitable

for a demonstration, but because of the lower melting temperature (48C), it is much safer

for students to work with that the mannite. A desktop coffee cup warmer is sufficient for

melting the salol on a glass slide. Because of the recess of the warmer's plate, it is best to

Wagenborg 50

set several large metal washers on the plate to raise its surface. The washers will conduct

the heat to the slide and make it easier to pick up the heated slide with forceps. Point out

to the students that they should be careful when heating the salol because overheating

will cause excessive evaporation and chemical odors, and will increase the time it takes

for the material to cool enough for crystallization to occur. The slide should be removed

from the hot plate just as it starts melting. The glass slide will retain enough heat to

complete the melting process.

Only a very small amount of Bismarck brown is needed for the last part of the activity

with salol. Only a few dozen grains are needed. Usually just touching the spatula to the

chemical causes enough particles to cling to it. Gently tap the spatula held over the

melted salol to transfer the particles. It will be easier to do this if the salol slide is placed

over a sheet of white paper. This will make it easier to see that the particles have landed

in the salol.

If students are permitted to do individual studies, go over the procedures while

demonstrating crystallization with the d-mannitol. Have students practice sketching the

crystallized mannitol samples before they try sketching the salol.

Refer to the chemical notes below for safety precautions required for this activity.

Notes On Chemicals Used: Bismarck Brown Y Bismarck brown is a stain used to dye

bone specimens for microscope slides. Because Bismarck brown is a stain, avoid getting

it on your fingers. Bismarck brown is water-soluble. Mannite (d-mannitol)

HOCH2(CHOH)4CH20H Mannite has a melting point of approximately 168C. It may be

harmful if inhaled or swallowed. Wear eye protection and gloves when handling this

chemical. Conduct the experiment in a well-ventilated area. Salol (phenyl salicylate)

C13H10O3 It has a melting point of 43 degrees C. It may irritate eyes. Wear eye

protection.

Procedure: Observations of Mannite

1.Place a small amount of mannite on a microscope slide and place the slide on a hot

plate. Raise the temperature of the hot plate until the mannite melts. Be careful not to

touch the hot plate or heated slide. Handle the slide with forceps.

2.After melting, cover the mannite with a cover glass and place the slide on a ceramic

bread-and- butter plate that has been chilled in a refrigerator. Permit the liquid mannite to

crystallize.

3.Observe the sample with a microprojector. Note the size, shape, number, and

boundaries of the crystals.

4.Prepare a second slide, but place it immediately on the micro projector stage. Permit the

mannite to cool slowly. Again observe the size, shape, and boundaries of the crystals.

Mark and save the two slides for comparison using student microscopes. Forty power is

sufficient for comparison. Have the students make sketches of the crystals on the two

slides and label them by cooling rate.

Wagenborg 51

Observations of Salol

1.Repeat the procedure for mannite (steps 1-4) with the salol, but do not use glass cover

slips. Use a desktop coffee cup warmer to melt the salol. It may be necessary to add a

seed crystal to the liquid on each slide to start the crystallization. Use a spatula to carry

the seed to the salol. If the seed melts, wait a moment and try again when the liquid is a

bit cooler. (If the micro projector you use does not have heat filters, the heat from the

lamp may re-melt the salol before crystallization is completed.)

2.Prepare a new salol slide and place it on the micro projector stage. Drop a tiny seed

crystal into the melt and observe the solid-liquid interface.

3.Remelt the salol on the slide and sprinkle a tiny amount of Bismarck brown on the melt.

Drop a seed crystal into the melt and observe the motion of the Bismarck brown granules.

The granules will make the movements of the liquid visible. Pay close attention to the

granules near the growing edges and points of the salol crystals.

Assessment: Collect the student data sheets.

Extensions:

Design a crystal-growing experiment that could be flown in space. The experiment

should be self-contained and the only astronaut involvement that of turning a switch on

and off.

Design a crystal-growing experiment for spaceflight that requires astronaut observations

and interpretations. Research previous crystal-growing experiments in space and some of

the potential benefits researchers expect from space-grown crystals.

Wagenborg 52

Wagenborg 53

Wagenborg 54

Wagenborg 55

Wagenborg 56

Wagenborg 57

Wagenborg 58

Wagenborg 59

Wagenborg 60

Performance Assessment

Choose three toys or common products that use motion to function and provide complete

descriptions in the graphic organizer below. Choose objects that we have not discussed.

You also may include drawings with your descriptions.

Toy or Common

Product

How gravity helps it work or

move (perform)

How do you think it will

perform in a microgravity

environment and why you

think this

Ohio Department of Education

http://ims.ode.state.oh.us/ODE/IMS/Default.asp?bhcp=1

Wagenborg 61

Sources

AAAS (1993). Benchmarks For Science Literacy. New York: Oxford University Press.

Amazing Space (2006). Formal Education Group of the Space Telescope Science

Institute's Office of Public Outreach.

http://amazing-space.stsci.edu/eds/

Dal, B. (2007). How Do We Help Students Build Beliefs That Allow Them to Avoid

Critical Learning Barriers and Develop A Deep Understanding of Geology?

Eurasia Journal of Mathematics, Science & Technology Education, 2007, 3(4),

251-269.

European Space Agency (ESA). (2007). Experiments in microgravity. Manned

Spacecrafts and Microgravity. Downloaded from

http://www.spaceflight.esa.int/file.cfm?filename=mgprogsexpts

Holt, Rinhart & Winston. (2004). Forces and Motion. Austin, Texas: Harcourt

Education Company.

NASA. (2007). Microgravity: A teacher’s guide with activities in science, mathematics

and technology. National Aeronautics and Space Administration, Office of Life

and Microgravity Sciences and Applications Microgravity Research Division,

Office of Human Resources and Education Division.

http://quest.nasa.gov/space/teachers/microgravity/index.html

NSTA. (1996). National Science Education Standards. National Academy Press.

Washington D.C.

Ohio’s Instructional Management System. (2008). Ohio Department of Education

http://ims.ode.state.oh.us/ODE/IMS/Default.asp?bhcp=1

Prescott, A. (2004) Student misconceptions about projectile motion. PHD Study,

Macquarie University.

http://www.merga.net.au/documents/RP722005.pdf

Thagard, P. (1992). Conceptual revolution. Princeton: Princeton University Press.

Vosniadou, S. (1994). Capturing and modelling the process of conceptual change.

Learning and Instruction, 4, 45-69.

Wiggins, G. & McTighe, J. (2005). Understanding By Design. Alexandria,VA:

Association for Supervision and Curriculum Development.

Date post:	02-Aug-2020
Category:	Documents
Upload:	others
View:	6 times
Download:	0 times

Space for Growth: Colloidal Crystallization in …bwagenbo/MISEPCapstoneProject.pdfWagenborg 3 Space...

Documents