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 <nicolas.f...@esrf.fr> 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.uk Douglas 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) 148-864-9090 US toll-free 1-877-225-2034 Regd. England 2177994, VAT Reg. GB 480 7371 36
