Ice Nucleation
Ice Nucleation
Introduction:
Background-
The creation of a new phase from a super cooled state occurs through germs. Germs are small, transient clusters of the new phase, or something approximating it, which exist in various sizes, dispersed within the parent phase. Continuous fluctuations in the sizes of these clusters may result in a germ growing large enough to become stable. This is expressed as reaching the critical size for stability, and hence nucleation of the new phase. The instability of germs smaller than the critical size and the stability of those larger than the critical size arise from the decreasing surface to volume ratio of the germ with increasing size. Molecules at the germ=s surface are most likely to return from the germ to the metastable phase, so that the higher is the proportion of interior molecules the more likely it is that the germ will become permanent and grow. There are two types of nucleation: homogeneous and heterogeneous nucleation. Homogeneous nucleation requires a greater degree of super cooling than Heterogeneous nucleation. Ice formation from the vapor phase is termed deposition, while ice nucleation from the liquid is termed freezing.
Objective-
By conducting this experiment we will test what causes the ice nucleation. It may either be the broth or the bacteria.
Hypothesis-
If the plain broth is added then the DDH2O will not nucleate.
Materials & Method:
Procedure-
The bench was cleaned with 70% ethanol. Distilled water in a test tube was placed in a supercooling bath of ice and ethanol. A drop of Pseudomonas syringae was added to the test tube and observed. The experiment was also conducted using broth in place of the syringae.
Method-
Two test tubes were used with distilled water in them. They were placed in a tub of ice and 100% ethanol was placed on the ice. Pipettes were used to collect the culture and broth. A thermometer was used. The...
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