Re: [ccp4bb] Slightly OT: crystallization teaching resources for kids

[Tim Gruene]

Dear Philippe,

I mixed up the signs and agree with you nice and much more quantitative 
explanation. 

Best,
Tim

On Thursday 05 January 2017 10:18:53 AM DUMAS Philippe wrote:
> Le Jeudi 5 Janvier 2017 08:56 CET, Tim Gruene  a écrit:
> 
> I did not follow all the previous details of this discussion, but I think
> one may say that the statement "The entropy of molecules arranged in a
> crystal must be greatly larger than in solution" is incorrect. Of course,
> there is an increase of entropy (DeltaS = S(solution) - S(crystal) > 0) 
> from the ordered crystalline state to the disordered solution state, hence
> S(crystal) < S(solution). Te nice thing is that, without knowing anything
> about the crystallization process, one can also say that DeltaS (per mole)
> = DeltaH/T, where T is the absolute temperature anf DeltaH > 0 is the heat
> absorbed by one mole of molecules going from the crystal state to the
> solution state during the melting of the crystal. Hence, the
> crystallization process, as with ice formation, produces heat (releases
> heat in the solution). Would one measure (in a calorimeter) the heat
> -DeltaH produced during crystallization,  and the number of molecules
> having formed the crystal, then one would obtain immediately the DeltaS of
> crystallization. To be accurate: all of that is correct as far as T is the
> equilibrium temperature where the two phases coexist and can exchange
> reversiby (i.e. DeltaG = DeltaH - T DeltaS = 0). For ice melting at
> atmospheric pressure this would be of course 273.15 K. Philippe Dumas
> 
> > Dear Nicolas,
> > 
> > are you sure this concept is correct?
> > 
> > The entropy of molecules arranged in a crystal must be greatly larger than
> > in solution. Hence the driving force for crystallisation is actually a
> > drop in energy, and I am not sure there is actually a barrier.
> > 
> > I would take the kids to the play ground and let them run around randomly.
> > When I blow a wistle they should line up in an orderly manner.
> > 
> > I am sure it will take some time before some sort of order is achieved,
> > for
> > the kids could face in various directions, or line up in blocks, or other
> > shapes. Once a seed is there, i.e. once e.g. 4-5 kids have created a
> > regular block, it will be much easier for the rest to line up (this is
> > consistent with Patrick's explanation).
> > 
> > Cheers,
> > Tim
> > 
> > On Wednesday 04 January 2017 05:45:50 PM Nicolas FOOS wrote:
> > > Dear Evette,
> > > 
> > > If I was is your situation (explaining nucleation and other concept). I
> > > will discuss in terms of energy.
> > > 
> > > I mean obtaining the initial nuclei is the "costly" step in terms of
> > > energy. To represent that, out the classical curve of energy, I will use
> > > a metaphoric representation such as jump over a barrier and run after.
> > > 
> > > With this analogy, it's possible to explain that the first step is
> > > 
> > > difficult and the second more accessible. If the barrier is to high,
> > > it's impossible to continue and run. If you don't have any barrier it's
> > > easy to run and if you only have a small barrier is not to difficult to
> > > jump over and run. But It also allow you to explain that if you
> > > facilitate the apparition of the first "surface" thanks to appropriate
> > > method (seeding, dust...) you can help the first step (to continue with
> > > the barrier story, it like you have ladder to help, or the ability to>
> > > decrease the size of the barrier.
> > > 
> > > For why the crystal and how, I will maybe use the example of orange
> > > pyramid in the food store. Orange are stable together because they have
> > > enough contact, because they have relatively homogeneous shape. If you
> > > mixed orange with water melon it's difficult to obtain nice pyramid.
> > > 
> > > For crystallization experiment which work, I have no Idea out of the one
> > > you already mentioned.
> > > 
> > > 
> > > Hope this help.
> > > 
> > > Nicolas
> > > 
> > > Nicolas Foos
> > > PhD
> > > Structural Biology Group
> > > European Synchrotron Radiation Facility (E.S.R.F)
> > > 71, avenue des Martyrs
> > > CS 40220
> > > 38043 GRENOBLE Cedex 9
> > > +33 (0)6 76 88 14 87
> > > +33 (0)4 76 88 45 19
> > > 
> > > On 30/12/2016 11:06, Radisky, Evette S., Ph.D. wrote:
> > > > Can anyone point to some especially useful resources to help explain
> > > > to kids (pre-chemistry, ~age 10-12) how and why molecules crystallize?
> > > > Maybe a good online movie or animation?  I am especially needing help
> > > > with the concept of nucleation, and why nucleation is slower and then
> > > > crystal growth faster once nuclei have formed.  I have been
> > > > supervising some experiments growing sucrose crystals from
> > > > supersaturated solutions, which have worked really well, but I am
> > > > having more difficulty in explaining the underlying fundamental
> > > > concepts in a way that is understandable to the kids.
> > > > 
> > > > 

Re: [ccp4bb] Slightly OT: crystallization teaching resources for kids

[Keller, Jacob]

Has anyone on the list heard of growing 5-minute lysozyme crystals in an ITC 
bomb? Seems like it should produce a nice measureable change in heat. I suspect 
it will be endothermic, not exo, but am not too confident.

JPK

-Original Message-
From: CCP4 bulletin board [mailto:CCP4BB@JISCMAIL.AC.UK] On Behalf Of DUMAS 
Philippe (VIE)
Sent: Thursday, January 05, 2017 4:19 AM
To: CCP4BB@JISCMAIL.AC.UK
Subject: Re: [ccp4bb] Slightly OT: crystallization teaching resources for kids

 
Le Jeudi 5 Janvier 2017 08:56 CET, Tim Gruene <tim.gru...@psi.ch> a écrit: 

I did not follow all the previous details of this discussion, but I think one 
may say that the statement "The entropy of molecules arranged in a crystal must 
be greatly larger than in solution" is incorrect.
Of course, there is an increase of entropy (DeltaS = S(solution) - S(crystal) > 
0)  from the ordered crystalline state to the disordered solution state, hence 
S(crystal) < S(solution). 
Te nice thing is that, without knowing anything about the crystallization 
process, one can also say that DeltaS (per mole) = DeltaH/T, where T is the 
absolute temperature anf DeltaH > 0 is the heat absorbed by one mole of 
molecules going from the crystal state to the solution state during the melting 
of the crystal. Hence, the crystallization process, as with ice formation, 
produces heat (releases heat in the solution). Would one measure (in a 
calorimeter) the heat -DeltaH produced during crystallization,  and the number 
of molecules having formed the crystal, then one would obtain immediately the 
DeltaS of crystallization.
To be accurate: all of that is correct as far as T is the equilibrium 
temperature where the two phases coexist and can exchange reversiby (i.e. 
DeltaG = DeltaH - T DeltaS = 0). For ice melting at atmospheric pressure this 
would be of course 273.15 K.
Philippe Dumas

> Dear Nicolas,
> 
> are you sure this concept is correct?
> 
> The entropy of molecules arranged in a crystal must be greatly larger 
> than in solution. Hence the driving force for crystallisation is 
> actually a drop in energy, and I am not sure there is actually a barrier.
> 
> I would take the kids to the play ground and let them run around randomly. 
> When I blow a wistle they should line up in an orderly manner.
> 
> I am sure it will take some time before some sort of order is 
> achieved, for the kids could face in various directions, or line up in 
> blocks, or other shapes. Once a seed is there, i.e. once e.g. 4-5 kids 
> have created a regular block, it will be much easier for the rest to 
> line up (this is consistent with Patrick's explanation).
> 
> Cheers,
> Tim
> 
> On Wednesday 04 January 2017 05:45:50 PM Nicolas FOOS wrote:
> > Dear Evette,
> > 
> > If I was is your situation (explaining nucleation and other 
> > concept). I will discuss in terms of energy.
> > 
> > I mean obtaining the initial nuclei is the "costly" step in terms of 
> > energy. To represent that, out the classical curve of energy, I will 
> > use a metaphoric representation such as jump over a barrier and run after.
> > 
> > With this analogy, it's possible to explain that the first step is

> > difficult and the second more accessible. If the barrier is to high, 
> > it's impossible to continue and run. If you don't have any barrier 
> > it's easy to run and if you only have a small barrier is not to 
> > difficult to jump over and run. But It also allow you to explain 
> > that if you facilitate the apparition of the first "surface" thanks 
> > to appropriate method (seeding, dust...) you can help the first step 
> > (to continue with the barrier story, it like you have ladder to help, or 
> > the ability to> decrease the size of the barrier.
> > 
> > For why the crystal and how, I will maybe use the example of orange 
> > pyramid in the food store. Orange are stable together because they 
> > have enough contact, because they have relatively homogeneous shape. 
> > If you mixed orange with water melon it's difficult to obtain nice pyramid.
> > 
> > For crystallization experiment which work, I have no Idea out of the 
> > one you already mentioned.
> > 
> > 
> > Hope this help.
> > 
> > Nicolas
> > 
> > Nicolas Foos
> > PhD
> > Structural Biology Group
> > European Synchrotron Radiation Facility (E.S.R.F) 71, avenue des 
> > Martyrs CS 40220
> > 38043 GRENOBLE Cedex 9
> > +33 (0)6 76 88 14 87
> > +33 (0)4 76 88 45 19
> > 
> > On 30/12/2016 11:06, Radisky, Evette S., Ph.D. wrote:
> > > Can anyone point to some especially useful resources to help 
> > > explain to kids (pre-chemistry, ~age 10-12) how 

Re: [ccp4bb] Slightly OT: crystallization teaching resources for kids

[VIE]

Le Jeudi 5 Janvier 2017 08:56 CET, Tim Gruene  a écrit:

I did not follow all the previous details of this discussion, but I think one 
may say that the statement "The entropy of molecules arranged in a crystal must 
be greatly larger than in solution" is incorrect.
Of course, there is an increase of entropy (DeltaS = S(solution) - S(crystal) > 
0)  from the ordered crystalline state to the disordered solution state, hence 
S(crystal) < S(solution).
Te nice thing is that, without knowing anything about the crystallization 
process, one can also say that DeltaS (per mole) = DeltaH/T, where T is the 
absolute temperature anf DeltaH > 0 is the heat absorbed by one mole of 
molecules going from the crystal state to the solution state during the melting 
of the crystal. Hence, the crystallization process, as with ice formation, 
produces heat (releases heat in the solution). Would one measure (in a 
calorimeter) the heat -DeltaH produced during crystallization,  and the number 
of molecules having formed the crystal, then one would obtain immediately the 
DeltaS of crystallization.
To be accurate: all of that is correct as far as T is the equilibrium 
temperature where the two phases coexist and can exchange reversiby (i.e. 
DeltaG = DeltaH - T DeltaS = 0). For ice melting at atmospheric pressure this 
would be of course 273.15 K.
Philippe Dumas

> Dear Nicolas,
>
> are you sure this concept is correct?
>
> The entropy of molecules arranged in a crystal must be greatly larger than in
> solution. Hence the driving force for crystallisation is actually a drop in
> energy, and I am not sure there is actually a barrier.
>
> I would take the kids to the play ground and let them run around randomly.
> When I blow a wistle they should line up in an orderly manner.
>
> I am sure it will take some time before some sort of order is achieved, for
> the kids could face in various directions, or line up in blocks, or other
> shapes. Once a seed is there, i.e. once e.g. 4-5 kids have created a regular
> block, it will be much easier for the rest to line up (this is consistent with
> Patrick's explanation).
>
> Cheers,
> Tim
>
> On Wednesday 04 January 2017 05:45:50 PM Nicolas FOOS wrote:
> > Dear Evette,
> >
> > If I was is your situation (explaining nucleation and other concept). I
> > will discuss in terms of energy.
> >
> > I mean obtaining the initial nuclei is the "costly" step in terms of
> > energy. To represent that, out the classical curve of energy, I will use
> > a metaphoric representation such as jump over a barrier and run after.
> >
> > With this analogy, it's possible to explain that the first step is

> > difficult and the second more accessible. If the barrier is to high,
> > it's impossible to continue and run. If you don't have any barrier it's
> > easy to run and if you only have a small barrier is not to difficult to
> > jump over and run. But It also allow you to explain that if you
> > facilitate the apparition of the first "surface" thanks to appropriate
> > method (seeding, dust...) you can help the first step (to continue with
> > the barrier story, it like you have ladder to help, or the ability to> 
> > decrease the size of the barrier.
> >
> > For why the crystal and how, I will maybe use the example of orange
> > pyramid in the food store. Orange are stable together because they have
> > enough contact, because they have relatively homogeneous shape. If you
> > mixed orange with water melon it's difficult to obtain nice pyramid.
> >
> > For crystallization experiment which work, I have no Idea out of the one
> > you already mentioned.
> >
> >
> > Hope this help.
> >
> > Nicolas
> >
> > Nicolas Foos
> > PhD
> > Structural Biology Group
> > European Synchrotron Radiation Facility (E.S.R.F)
> > 71, avenue des Martyrs
> > CS 40220
> > 38043 GRENOBLE Cedex 9
> > +33 (0)6 76 88 14 87
> > +33 (0)4 76 88 45 19
> >
> > On 30/12/2016 11:06, Radisky, Evette S., Ph.D. wrote:
> > > Can anyone point to some especially useful resources to help explain
> > > to kids (pre-chemistry, ~age 10-12) how and why molecules crystallize?
> > > Maybe a good online movie or animation?  I am especially needing help
> > > with the concept of nucleation, and why nucleation is slower and then
> > > crystal growth faster once nuclei have formed.  I have been
> > > supervising some experiments growing sucrose crystals from
> > > supersaturated solutions, which have worked really well, but I am
> > > having more difficulty in explaining the underlying fundamental
> > > concepts in a way that is understandable to the kids.
> > >
> > > Thanks!
> > > Evette
> > >
> > > Evette Radisky, PhD
> > >
> > > Associate Professor of Cancer Biology
> > >
> > > Mayo Clinic Cancer Center
> > >
> > > Griffin Cancer Research Building
> > >
> > > 4500 San Pablo Road 
> > >
> > > Jacksonville, FL 32224 
> > >
> > > tel: 904-953-6372 
> > >
> > > fax: 904-953-0277 
> --
> --
> Paul Scherrer Institut
> Dr. Tim Gruene
> - 

Re: [ccp4bb] Slightly OT: crystallization teaching resources for kids

[Frank von Delft]

I reckon you compare it to something going viral on the intertubes - 
most posts or videos do nothing, they only go viral if enough people 
share them.



On 05/01/2017 07:56, Tim Gruene wrote:

Dear Nicolas,

are you sure this concept is correct?

The entropy of molecules arranged in a crystal must be greatly larger than in
solution. Hence the driving force for crystallisation is actually a drop in
energy, and I am not sure there is actually a barrier.

I would take the kids to the play ground and let them run around randomly.
When I blow a wistle they should line up in an orderly manner.

I am sure it will take some time before some sort of order is achieved, for
the kids could face in various directions, or line up in blocks, or other
shapes. Once a seed is there, i.e. once e.g. 4-5 kids have created a regular
block, it will be much easier for the rest to line up (this is consistent with
Patrick's explanation).

Cheers,
Tim

On Wednesday 04 January 2017 05:45:50 PM Nicolas FOOS wrote:

Dear Evette,

If I was is your situation (explaining nucleation and other concept). I
will discuss in terms of energy.

I mean obtaining the initial nuclei is the "costly" step in terms of
energy. To represent that, out the classical curve of energy, I will use
a metaphoric representation such as jump over a barrier and run after.

With this analogy, it's possible to explain that the first step is
difficult and the second more accessible. If the barrier is to high,
it's impossible to continue and run. If you don't have any barrier it's
easy to run and if you only have a small barrier is not to difficult to
jump over and run. But It also allow you to explain that if you
facilitate the apparition of the first "surface" thanks to appropriate
method (seeding, dust...) you can help the first step (to continue with
the barrier story, it like you have ladder to help, or the ability to
decrease the size of the barrier.

For why the crystal and how, I will maybe use the example of orange
pyramid in the food store. Orange are stable together because they have
enough contact, because they have relatively homogeneous shape. If you
mixed orange with water melon it's difficult to obtain nice pyramid.

For crystallization experiment which work, I have no Idea out of the one
you already mentioned.


Hope this help.

Nicolas

Nicolas Foos
PhD
Structural Biology Group
European Synchrotron Radiation Facility (E.S.R.F)
71, avenue des Martyrs
CS 40220
38043 GRENOBLE Cedex 9
+33 (0)6 76 88 14 87
+33 (0)4 76 88 45 19

On 30/12/2016 11:06, Radisky, Evette S., Ph.D. wrote:

Can anyone point to some especially useful resources to help explain
to kids (pre-chemistry, ~age 10-12) how and why molecules crystallize?
Maybe a good online movie or animation?  I am especially needing help
with the concept of nucleation, and why nucleation is slower and then
crystal growth faster once nuclei have formed.  I have been
supervising some experiments growing sucrose crystals from
supersaturated solutions, which have worked really well, but I am
having more difficulty in explaining the underlying fundamental
concepts in a way that is understandable to the kids.

Thanks!
Evette

Evette Radisky, PhD

Associate Professor of Cancer Biology

Mayo Clinic Cancer Center

Griffin Cancer Research Building

4500 San Pablo Road 

Jacksonville, FL 32224 

tel: 904-953-6372 

fax: 904-953-0277 

Re: [ccp4bb] Slightly OT: crystallization teaching resources for kids

[Tim Gruene]

Dear Nicolas,

are you sure this concept is correct?

The entropy of molecules arranged in a crystal must be greatly larger than in 
solution. Hence the driving force for crystallisation is actually a drop in 
energy, and I am not sure there is actually a barrier.

I would take the kids to the play ground and let them run around randomly. 
When I blow a wistle they should line up in an orderly manner.

I am sure it will take some time before some sort of order is achieved, for 
the kids could face in various directions, or line up in blocks, or other 
shapes. Once a seed is there, i.e. once e.g. 4-5 kids have created a regular 
block, it will be much easier for the rest to line up (this is consistent with 
Patrick's explanation).

Cheers,
Tim

On Wednesday 04 January 2017 05:45:50 PM Nicolas FOOS wrote:
> Dear Evette,
> 
> If I was is your situation (explaining nucleation and other concept). I
> will discuss in terms of energy.
> 
> I mean obtaining the initial nuclei is the "costly" step in terms of
> energy. To represent that, out the classical curve of energy, I will use
> a metaphoric representation such as jump over a barrier and run after.
> 
> With this analogy, it's possible to explain that the first step is
> difficult and the second more accessible. If the barrier is to high,
> it's impossible to continue and run. If you don't have any barrier it's
> easy to run and if you only have a small barrier is not to difficult to
> jump over and run. But It also allow you to explain that if you
> facilitate the apparition of the first "surface" thanks to appropriate
> method (seeding, dust...) you can help the first step (to continue with
> the barrier story, it like you have ladder to help, or the ability to
> decrease the size of the barrier.
> 
> For why the crystal and how, I will maybe use the example of orange
> pyramid in the food store. Orange are stable together because they have
> enough contact, because they have relatively homogeneous shape. If you
> mixed orange with water melon it's difficult to obtain nice pyramid.
> 
> For crystallization experiment which work, I have no Idea out of the one
> you already mentioned.
> 
> 
> Hope this help.
> 
> Nicolas
> 
> Nicolas Foos
> PhD
> Structural Biology Group
> European Synchrotron Radiation Facility (E.S.R.F)
> 71, avenue des Martyrs
> CS 40220
> 38043 GRENOBLE Cedex 9
> +33 (0)6 76 88 14 87
> +33 (0)4 76 88 45 19
> 
> On 30/12/2016 11:06, Radisky, Evette S., Ph.D. wrote:
> > Can anyone point to some especially useful resources to help explain
> > to kids (pre-chemistry, ~age 10-12) how and why molecules crystallize?
> > Maybe a good online movie or animation?  I am especially needing help
> > with the concept of nucleation, and why nucleation is slower and then
> > crystal growth faster once nuclei have formed.  I have been
> > supervising some experiments growing sucrose crystals from
> > supersaturated solutions, which have worked really well, but I am
> > having more difficulty in explaining the underlying fundamental
> > concepts in a way that is understandable to the kids.
> > 
> > Thanks!
> > Evette
> > 
> > Evette Radisky, PhD
> > 
> > Associate Professor of Cancer Biology
> > 
> > Mayo Clinic Cancer Center
> > 
> > Griffin Cancer Research Building
> > 
> > 4500 San Pablo Road 
> > 
> > Jacksonville, FL 32224 
> > 
> > tel: 904-953-6372 
> > 
> > fax: 904-953-0277 
-- 
--
Paul Scherrer Institut
Dr. Tim Gruene
- persoenlich -
Principal Investigator
Biology and Chemistry
OFLC/102
CH-5232 Villigen PSI

Phone: +41 (0)56 310 5297

GPG Key ID = A46BEE1A



signature.asc
Description: This is a digitally signed message part.

Re: [ccp4bb] Slightly OT: crystallization teaching resources for kids

[Patrick Shaw Stewart]

Yes, but the kids will want to know WHY there is an energy barrier.

I prefer my explanation below.

Happy New Year to all

Patrick
_

> I am especially needing help with the concept of nucleation, and why
nucleation is slower and then crystal growth faster once nuclei have
formed.

I always explain this by pointing out that, when the crystal is very small,
each new molecule that lands on the surface of the nascent crystal can only
be attached on one or two sides.  When the crystal is larger, molecules
that land are more likely to become attached on two, three or more sides.

Atomic force microscopy images of "islands" that appear on the faces of
crystals are also helpful.  Islands are more likely to appear on larger
faces.  Once they appear they can rapidly spread to the edges of the
crystal, which is (one mechanism explaining) why crystals have flat faces.





On 4 January 2017 at 16:45, Nicolas FOOS  wrote:

> Dear Evette,
>
> If I was is your situation (explaining nucleation and other concept). I
> will discuss in terms of energy.
>
> I mean obtaining the initial nuclei is the "costly" step in terms of
> energy. To represent that, out the classical curve of energy, I will use a
> metaphoric representation such as jump over a barrier and run after.
>
> With this analogy, it's possible to explain that the first step is
> difficult and the second more accessible. If the barrier is to high, it's
> impossible to continue and run. If you don't have any barrier it's easy to
> run and if you only have a small barrier is not to difficult to jump over
> and run. But It also allow you to explain that if you facilitate the
> apparition of the first "surface" thanks to appropriate method (seeding,
> dust...) you can help the first step (to continue with the barrier story,
> it like you have ladder to help, or the ability to decrease the size of the
> barrier.
>
> For why the crystal and how, I will maybe use the example of orange
> pyramid in the food store. Orange are stable together because they have
> enough contact, because they have relatively homogeneous shape. If you
> mixed orange with water melon it's difficult to obtain nice pyramid.
>
> For crystallization experiment which work, I have no Idea out of the one
> you already mentioned.
>
>
> Hope this help.
>
> Nicolas
>
> Nicolas Foos
> PhD
> Structural Biology Group
> European Synchrotron Radiation Facility (E.S.R.F)
> 71, avenue des Martyrs
> CS 40220
> 38043 GRENOBLE Cedex 9+33 (0)6 76 88 14 87 <+33%206%2076%2088%2014%2087>+33 
> (0)4 76 88 45 19 <+33%204%2076%2088%2045%2019>
>
> On 30/12/2016 11:06, Radisky, Evette S., Ph.D. wrote:
>
> Can anyone point to some especially useful resources to help explain to
> kids (pre-chemistry, ~age 10-12) how and why molecules crystallize? Maybe a
> good online movie or animation?  I am especially needing help with the
> concept of nucleation, and why nucleation is slower and then crystal growth
> faster once nuclei have formed.  I have been supervising some experiments
> growing sucrose crystals from supersaturated solutions, which have worked
> really well, but I am having more difficulty in explaining the underlying
> fundamental concepts in a way that is understandable to the kids.
>
> Thanks!
> Evette
>
> Evette Radisky, PhD
>
> Associate Professor of Cancer Biology
>
> Mayo Clinic Cancer Center
>
> Griffin Cancer Research Building
>
> 4500 San Pablo Road
>
> Jacksonville, FL 32224
>
> tel: 904-953-6372
>
> fax: 904-953-0277
>
>
>


-- 
 patr...@douglas.co.ukDouglas Instruments Ltd.
 Douglas House, East Garston, Hungerford, Berkshire, RG17 7HD, UK
 Directors: Peter Baldock, Patrick Shaw Stewart

 http://www.douglas.co.uk
 Tel: 44 (0) 148-864-9090US toll-free 1-877-225-2034
 Regd. England 2177994, VAT Reg. GB 480 7371 36

Re: [ccp4bb] Slightly OT: crystallization teaching resources for kids

[Nicolas FOOS]

Dear Evette,

If I was is your situation (explaining nucleation and other concept). I 
will discuss in terms of energy.


I mean obtaining the initial nuclei is the "costly" step in terms of 
energy. To represent that, out the classical curve of energy, I will use 
a metaphoric representation such as jump over a barrier and run after.


With this analogy, it's possible to explain that the first step is 
difficult and the second more accessible. If the barrier is to high, 
it's impossible to continue and run. If you don't have any barrier it's 
easy to run and if you only have a small barrier is not to difficult to 
jump over and run. But It also allow you to explain that if you 
facilitate the apparition of the first "surface" thanks to appropriate 
method (seeding, dust...) you can help the first step (to continue with 
the barrier story, it like you have ladder to help, or the ability to 
decrease the size of the barrier.


For why the crystal and how, I will maybe use the example of orange 
pyramid in the food store. Orange are stable together because they have 
enough contact, because they have relatively homogeneous shape. If you 
mixed orange with water melon it's difficult to obtain nice pyramid.


For crystallization experiment which work, I have no Idea out of the one 
you already mentioned.



Hope this help.

Nicolas

Nicolas Foos
PhD
Structural Biology Group
European Synchrotron Radiation Facility (E.S.R.F)
71, avenue des Martyrs
CS 40220
38043 GRENOBLE Cedex 9
+33 (0)6 76 88 14 87
+33 (0)4 76 88 45 19

On 30/12/2016 11:06, Radisky, Evette S., Ph.D. wrote:
Can anyone point to some especially useful resources to help explain 
to kids (pre-chemistry, ~age 10-12) how and why molecules crystallize? 
Maybe a good online movie or animation?  I am especially needing help 
with the concept of nucleation, and why nucleation is slower and then 
crystal growth faster once nuclei have formed.  I have been 
supervising some experiments growing sucrose crystals from 
supersaturated solutions, which have worked really well, but I am 
having more difficulty in explaining the underlying fundamental 
concepts in a way that is understandable to the kids.


Thanks!
Evette

Evette Radisky, PhD

Associate Professor of Cancer Biology

Mayo Clinic Cancer Center

Griffin Cancer Research Building

4500 San Pablo Road 

Jacksonville, FL 32224 

tel: 904-953-6372 

fax: 904-953-0277