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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
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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.
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Space for Growth: Colloidal Crystallization in Microgravity
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).
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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.
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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
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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
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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).
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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
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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
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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.
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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).
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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.
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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.
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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.
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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).
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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).
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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.
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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
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“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
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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.
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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).
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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
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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).
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Figure 12: PHaSE results: Larger colloidal crystals grew with the f.c.c. structure
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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).
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Figure 13: PCS results: binary colloidal crystal growth in microgravity
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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
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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
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Interfaces. Retrieved from: http://www.mpikg-golm.mpg.de/kc/
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DLVO theory fails for biological and colloidal systems. Physical Review
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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.
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Cape Canaveral, Florida. October 15-18, 2001.
Van Blaaderen, A. Ruel, R., Wiltzius, P. (1997). Template-directed colloidal
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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
Space for Growth: Colloidal Crystallization in Microgravity
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.
E.U.: Creating and investigating scientific models allows us to observe phenomena that
are impossible to completely recreate on Earth.
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.
E.U.: Creating and investigating scientific models allows us to observe phenomena that
are impossible to completely recreate on Earth.
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.
E.U.: Creating and investigating scientific models allows us to observe phenomena that
are impossible to completely recreate on Earth.
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.
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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
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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.
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*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
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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.
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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
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“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
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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.
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“Around The World”
(NASA, 2007)
Objective: · To create a model of how satellites
orbit Earth.
Science Standards: Science as Inquiry,
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.
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Crystallization Model”
(NASA, 2007)
Objective: · To demonstrate how atoms in a
solid arrange themselves.
Science Standards: Science as Inquiry,
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.
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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.
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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.
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“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.
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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.
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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
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