These are flashcards an notes made by students on topics like 'molecules', 'crystals' and 'transition', originating from:

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- Wageningen University
ISBN-13 9990002019708
665 Flashcards & Notes
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Study Cards on molecules, crystals, transition

What is the rate of crystal growth dependent on?
The diffusion rate.
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Why does the crystal growth have a maximum?
The diffusion rate decreases with lower temperatures and higher concentrations (viscosity).
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How do the graphs look of crystal growth vs. Temperature and concentration when the solution is far away from the glass transition? And when it is close to the glass transition?
Like this.
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Why does a crystal have a specific shape?
Because the crystals do not grow equally fast at all sides. They grow at specific sides where the molecules can easily fit in the regular pattern in which the molecules are arranged in the crystal. On other faces, the molecules can grow but much more slowly (they have to be distorted) or not at all (they don't fit). This causes the crystal not be spherical, but having a specific shape: hexagonal (8 growing faces), cubic (6 growing faces) or needle-shaped (2 growing faces) or other shapes.
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What is the induction time?
A time before the significant crystallization takes place. This time is the time needed for nucleation and the time needed for crystal growth. The time is infinitely long when the supersaturation (or supercooling) is zero, and also infinitely large at the glass transition, as the whole system is immobilised at that point.
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Why do crystals become very regular when they grow slowly?
Branching occurs. Due to an error in the arrangement of the molecules on the growing surface, the growing face splits up, and from the face, two or even more faces start to grow.
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What is a spherulite?
A sphere containing fat crystals, surrounded by liquid oil. A spherulite is porous and only partly crystalline. It can be found at the bottom of olive oil when stored at colder temperature.
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