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Topic: Freezing point


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In the News (Tue 10 Nov 09)

  
  Freezing Point - MSN Encarta
The freezing point of a pure (unmixed) liquid is essentially the same as the melting point of the same substance in its solid form and may be regarded as the temperature at which the solid and liquid states of the substance are in equilibrium.
Hence, the freezing point or melting point of a pure substance may also be defined as the temperature at which freezing or melting continues once it has commenced.
The molecular weight of an unknown or unidentified substance may be determined by measuring the amount by which the freezing point of a solvent is lowered when a known amount of the unidentified substance is dissolved in it.
encarta.msn.com /encyclopedia_761555245/Freezing_Point.html   (520 words)

  
 The MSDS HyperGlossary: Freezing Point
Freezing point is the temperature at which a liquid becomes a solid at normal atmospheric pressure.
The normal freezing point is the temperature at a substance melts (or freezes) at one atmosphere (760 torr = 760 mm Hg = 14.7 psi = 101.3 kPa) of pressure.
Melting points may be lowered (depressed) by the addition of a soluble material to the solution.
www.ilpi.com /msds/ref/freezingpoint.html   (335 words)

  
 Theoretical Aspects of Freezing
Note that C' is not as high as C, because the initial freezing point is depressed as a result of the solute.
The freezing time is usually defined as the time from the onset of nucleation to the endof the crystal growth phase.
The freezing curve predicts the amount of ice at any given temperature, which is a function of freezing point depression and hence the number of solutes (concentration of sugar, etc.).
www.foodsci.uoguelph.ca /dairyedu/freeztheor.html   (1930 words)

  
 Freezing and Food Safety
Freezing preserves food for extended periods because it prevents the growth of microorganisms that cause both food spoilage and foodborne illness.
Freeze unopened vacuum packages as is. If you notice that a package has accidentally been torn or has opened while food is in the freezer, the food is still safe to use; merely overwrap or rewrap it.
When it is freezing outside and there is snow on the ground, it seems like a good place to keep food until the power comes on; however, frozen food can thaw if it is exposed to the sun's rays even when the temperature is very cold.
www.fsis.usda.gov /Fact_Sheets/Focus_On_Freezing/index.asp   (1977 words)

  
 Freezing Point Depression   (Site not responding. Last check: 2007-11-04)
Freezing point depression is not just another way of referring to the early February blues.
For example, consider the effect that salt has on the melting point of ice (which is the same as the freezing point of water).
In general, for dilute solutions, the amount of change in the freezing point is proportional to the concentration of the solute in the solution.
dl.clackamas.cc.or.us /ch105-03/freezing.htm   (201 words)

  
 Molar Mass by Freezing-Point Depression   (Site not responding. Last check: 2007-11-04)
is the freezing point depression constant for a particular solvent (20.5°C-kg/mol for cyclohexane in this experiment), and m is the molality of the solution (in mol solute/kg solvent).
To determine the freezing temperature of pure cyclohexane, you need to determine the mean (or average) temperature in the portion of graph with nearly constant temperature.
To determine the freezing point of the solution, you need to determine the temperature at which the mixture first started to freeze.
www.pitt.edu /~n3lsk/0114/molarmasscycloproc.html   (635 words)

  
 Study Guide:Melting,Freezing & Boiling Point   (Site not responding. Last check: 2007-11-04)
Melting point, freezing point, and boiling point are characteristic properties of chemical substances.When a solid substance is heated, it will reach a specific temperature at which it begins to melt (become liquid).
Generally, for a particular substance, the melting point temperature and freezing point temperature are the same.
The melting, freezing, and boiling point temperatures of a substance are physical properties useful to a scientist.
www.thesciencedesk.com /sgmeltfreezboil.htm   (302 words)

  
 Freezing Point of 40% Isopropyl
The change in freezing point of the solution is the freezing point depression constant of water (-1.86 C per mole solute per kilogram solvent) multiplied by the solution's molality.
This means that for every mole of solute dissolved per kilogram of solvent, the freezing point of water drops by 1.86 C from water's actual freezing point of 0 C (32 F).
Water freezes to form ice and the higher concentration of isopropanol in the remaining liquid lowers the freezing point further, and more water ice forms.
www.newton.dep.anl.gov /askasci/chem00/chem00924.htm   (812 words)

  
 This concept should be kept in mind during the discussion of the following theories that have attempted to define the ...   (Site not responding. Last check: 2007-11-04)
Amazingly, it was very recently reported that freezing point of beer ovarian function was restored by successfully grafting ovarian tissue in a human..
This is freezing point of beer due to the partial disruption of the membrane which causes a block to the conventional fusion and penetration of sperm with the egg surface..
Freezing tolerance was lost after only 1 d of deacclimation at control temperatures, freezing point of beer and this change was associated with a large reduction in sugar content..
bonkavower.xoompages.com /hugley-piment.html   (1347 words)

  
 Leading Publication Shut Down In China   (Site not responding. Last check: 2007-11-04)
The decision to shut down Freezing Point, a four-page weekly feature section of the state-run China Youth Daily that often tested the censors and challenged the party line, came less than a month after the authorities replaced the top editors of another daring newspaper, the Beijing News.
Because any move to punish it would almost certainly require his approval, the decision to close Freezing Point was seen as further evidence of Hu's personal support for a tightening of controls on the media that began two years ago, about a year after Hu took office.
Party officials summoned the senior editors of the China Youth Daily and ordered Freezing Point closed a day after distributing a five-page document that accused the section of "viciously attacking the socialist system" and condemned a recent article in it that criticized the history textbooks used in Chinese middle schools.
www.washingtonpost.com /wp-dyn/content/article/2006/01/24/AR2006012401003_pf.html   (641 words)

  
 Freezing @ iCookClub.com
In physics and chemistry, freezing is the process of cooling a liquid to the temperature (called freezing point) where it turns solid.
The freezing point for water is only the same temperature as the melting point when nucleators are present to prevent supercooling.
Freezing is a common method of food preservation which slows both food decay and the growth of micro-organisms and, by turning water to ice, makes it unavailable for bacterial growth and chemical reactions (see frozen food).
reference.icookclub.com /freezing.html   (280 words)

  
 Aicompanies.com - osmometer, freezing point, osmol gap, milk quality pasteurization
Advanced Instruments, Inc. presented the world's fastest freezing point osmometer, to the biotechnology industry, at the 2007 BioProcess International show in October 2007.
Founded in 1955, the company is the world's foremost authority for the application of freezing point depression (FPD) technology.
An osmometry, a measurement of osmolality by the freezing point method, is an important diagnostic method used in a broad range of clinical applications not currently available by any other means with added water that is like milk quality.
www.aicompanies.com   (932 words)

  
 Milk Composition - Freezing Point
point of milk: Freezing point of a solution depends on the number of particles in the solvent (water phase of milk), rather than the kind of particles.
The current official freezing point limit (-0.525 degrees Horvet or -0.505 degrees C; see Sherbon 1988 for discussion of Horvet vs Centigrade) was designed for whole-herd, bulk-tank samples or processed milk samples, and not for samples from individual cows or individual quarters.
However, freezing point of milk as a regulatory standard is really only valid for milk pooled form many cows (bulk tank milk).
classes.aces.uiuc.edu /AnSci308/Milkcompsynth/milkcomp_freezing.html   (353 words)

  
 Freezing-Point Depression   (Site not responding. Last check: 2007-11-04)
Record the freezing temperature of pure lauric acid in your data table (round to the nearest 0.1°C).
Examine the data points to locate the freezing point of the solution, as shown in Figure 2.
Record the freezing point in the Data and Calculations table (round to 0.1°C).
www.sas.upenn.edu /~tloschia/AP/labs/FPD.htm   (717 words)

  
 Freezing Point Depression
The freezing points will be obtained by studying the rate at which liquid stearic acid and some of its solutions containing the unknown cool in air.
The freezing point of the pure liquid is the constant temperature observed while the liquid is freezing to a solid.
Near the freezing point you will begin observing solid stearic acid in the liquid, and the solid phase will increase in amount as cooling proceeds until the stearic acid is a solid mass.
www.cod.edu /people/faculty/fullerd/Experiments/FPDepression02/FreezingPtDepression.html   (2348 words)

  
 FREEZING STRESS   (Site not responding. Last check: 2007-11-04)
The presence of dew or misting raises the freezing point of the leaves and causes frost injury to occur at warmer temperatures.
Sugars may depress the freezing point of the tissue, act as a nutrient and energy reserve, alter phase properties of membranes in the dry state, act as a cryoprotectant to preserve protein structure and function, or influence glass formation at low temperatures.
Enrichment of non-acclimated protoplasts with the lipids from acclimated protoplasts, or with mono- or with di-unsaturated phosphatidylcholine increased freezing tolerance.
cropsoil.psu.edu /Courses/AGRO518/FREEZING.htm   (14479 words)

  
 Freezing Point Depression
It is extremely inaccurate to determine the molecular mass of a weak acid by freezing point depression.
Not to mention the fact that it is not stated that it is water freezing point depression...
It means that the liquid substance of known freezing point freezes at lower temperature, when there is something dissolved.
www.physicsforums.com /showthread.php?t=77256   (1030 words)

  
 Melting point - Wikipedia, the free encyclopedia
For example, the melting point and freezing point of the element mercury is 234.32 kelvins (−38.83 °C or −37.89 °F).
Unlike the boiling point, the melting point is relatively insensitive to pressure.
Melting points are often used to characterise organic compounds and to ascertain the purity.
en.wikipedia.org /wiki/Melting_point   (381 words)

  
 Freezing Point Depression   (Site not responding. Last check: 2007-11-04)
The freezing point of the solvent (the temperature at which solid and liquid phases are in equilibrium) is determined by cooling the solution and plotting a graph of temperature as a function of time.
However, a solution will freeze over a range of temperatures and will not exhibit the constant freezing point of the pure liquid; instead of exhibiting a horizontal portion, the plot will show a change of slope when solid solvent begins to form.
In practice, it is necessary to first determine the freezing point of the solvent alone, since the solvent may not be pure.
web.centre.edu /shiba/che132L/frz_pt.htm   (1653 words)

  
 Salt and the Freezing Point of Water .....................................
The water and ice are at 0°C, which is the melting point of ice and the freezing point of water.
Molecules of ice are constantly escaping into the water (melting), and molecules of water are being captured on the surface of the ice (freezing).
The higher the concentration of salt, the lower the freezing point drops.
www.worsleyschool.net /science/files/saltandfreezing/ofwater.html   (1091 words)

  
 Freezing point depression   (Site not responding. Last check: 2007-11-04)
The depression of the freezing point of a solution with respect to the pure solvent is analogous to boiling point elevation.
Thus, at the freezing point of a solution, the solvent in the solution and the solvent in the solid (which is composed only of solvent) must coexist.
This is the triple point on the phase diagram, as this is the point at which all three phases coexist.
nyu.edu /classes/tuckerman/honors.chem/lectures/lecture_13/node8.html   (271 words)

  
 FREEZING POINT DEPRESSION   (Site not responding. Last check: 2007-11-04)
The vapor pressure is lowered, the boiling point is raised, and the freezing point is lowered.
For dilute solutions, the decrease in freezing point and the increase in boiling point are directly proportional to the number of moles of solute particles dissolved per 1000 grams of solvent (molality).
Both the freezing of the ice cream and the decrease in temperature of the snow-salt mixtures represent a loss of heat.
www.oswego.edu /wscp/fp.htm   (872 words)

  
 The Freezing of Human Oocytes (Eggs)
Cryoprotectant is the term used to refer to the fluid that is used to place the eggs in prior to freezing, and is usually a mixture of sugars and organic chemical liquids that are designed to buffer the egg cell during the stresses of freezing and thawing.
To put egg freezing into context, it is interesting to consider that human sperm (spermatozoa) have been successfully frozen for decades, and that the first successful report of human embryo freezing that generated a pregnancy was in 1983.
As the initial concerns with egg freezing are being eroded by better understanding of the principals of cryopreserving such large and delicate cells, and by better technology, there becomes less and less reason not to start taking this form of tissue storage more seriously.
www.ivf.com /freezing.html   (3166 words)

  
 Freezing Point Depression   (Site not responding. Last check: 2007-11-04)
The purpose of this lab is to determine how much the freezing point of a pure substance changes when impurities are added.
T is the amount the freezing point lowers or “depresses”, k is a constant unique to every substance, and m is molality, defined as “moles of solute per kilogram of solvent.”
The purpose of this activity is to determine the freezing point depression constant for naphthalene, and to compare our experimental value to the accepted value.
www.dbooth.net /mhs/chem/colligative01.html   (313 words)

  
 EastSouthWestNorth: The Li-Lu Statement on Freezing  Point
Previously, Freezing Point had been ordered by the editor-in-chief to withdraw or swap articles numerous times, and that is a normal phenomenon in newspaper publishing.
During the reorganization period of Freezing Point weekly magazine, there must a serious attempt to summary the lessons, to rectify the idea of the direction of the pubcation, to perfect the regulatory system, to define the process of publication clearly and to implement the system of responsibility.
Bingdian, or Freezing Point, was a weekly insert in the China Youth Daily that made a name for itself by running in-depth reports on social issues and corruption.
www.zonaeuropa.com /20060218_2.htm   (3782 words)

  
 ChemTeam: Boiling Point Elevation and Freezing Point Depression
In the 1880's, when van 't Hoff was compiling and examining boiling point and freezing point data, he did not understand what i meant.
For example, pure water has a boiling point of 100 °C and a freezing point of 0 °C. In boiling for example, as pure water vapor leaves the liquid, only pure water is left behind.
The ratio with the lowest point is called a "eutectic" alloy; a 63 parts tin to 37 parts lead electrical solder is one such eutectic mixture.
dbhs.wvusd.k12.ca.us /webdocs/Solutions/BP-Elev-and-FP-Lower.html   (959 words)

  
 EastSouthWestNorth: From Binyan to Freezing Point   (Site not responding. Last check: 2007-11-04)
In the latter case, the Freezing Point weekly magazine was suspended for re-organization, and the chief editor Li Datong and the deputy editor Lu Yuegang were both relieved of their duties.
Freezing Point can resume publication, the Freezing Point team can still be said to exist, and Li Datong and Lu Yuegang did not fall into Liu Binyan's condition back then.
Freezing Point appeared precisely in this atmosphere of reform in journalism.
www.zonaeuropa.com /20060405_1.htm   (2829 words)

  
 RFA: ‘Freezing Point’ Journalists Hit Out at Chinese Government Over Press Freedom
Freezing Point will be reinstated without them in March, and one of the first articles it will carry will criticize prominent historian Yuan Weishi, whose article on the official versions of Chinese history sparked the row in the first place.
Li and Lu said top officials appeared particularly angry at the amount of exposure given to the row over Freezing Point in overseas media, and cited their granting of interviews to foreign media organizations as a key factor in the government’s decision to transfer them.
Freezing Point is one of the most courageous publications in China,” U.S.-based commentator Hu Ping said during the panel discussion.
www.rfa.org /english/news/politics/2006/02/17/china_freezingpoint   (781 words)

  
 General Chemistry Online: FAQ: Solutions: How can freezing point depression be explained in terms of free energies?
is the freezing point of the pure water.
The lower chemical potential of solution water shifts the point of intersection to the left, so the freezing point of the solution is lower than the freezing point of the pure solvent.
That would suggest that equal concentrations of ions or molecules cause equal freezing point depressions, regardless of what the solute is. Experimental results agree with this prediction, so long as the concentrations are low.
antoine.frostburg.edu /chem/senese/101/solutions/faq/thermo-explanation-of-freezingpoint-depression.shtml   (888 words)

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