1. Describe what happens on a particle level at the boiling point of a liquid.
2. Determine boiling point temperatures using a vapor pressure curve; compare and contrast intermolecular forces of a substance using the data on a vapor pressure curve.
3. Explain on a particle basis why a solution has a lower vapor pressure, an elevated boiling point, and a depressed freezing point, compared to that of the pure solvent.
4. Calculate the molality (m) of a solution, moles of solute or kilograms of solvent given the other 2 variables; calculate the change in boiling point or freezing point temperature based on the molality (m) of a solution.
Here's a video describing vapor pressure and boiling:
A series of curves on one set of axes can be shown. Here is one graph used in NYS Regents Chemistry:
Here's a lab to determine the vapor pressure of water at various temperatures so that students can graph it. I like that it's pretty reasonable to gather the materials and to perform.
Remember eye safety goggles and aprons
Here is a lecture about intermolecular forces and the effect on boiling point temperature. The discussion is very fast but very comprehensive -- you may have to view it more than once to better follow this discussion:
You may wonder about why all this talking about vapor pressure and boiling? Because a solute has an effect on boiling point and freezing point. This is a video demonstrating solute affecting boiling point and freezing point. This seems to be a student video and has a few misspellings -- oops!
But wait! What is molality? You may remember my discussion Molarity a few days ago. Here is a brief discussion (5 minutes) of molarity (M) vs. molality (m):
Here is a worksheet with answers and strategy suggestions:
Salt lowering the freezing point temperature of ice has a few practical applications. It is commonly used on icy roads and sidewalks to lower the freezing point temperature and prevent ice formation.
States are trying a variety of solvents other than salt to save money. Here's Massachusetts' webpage that contains a table of the salt fighting substances:
For making ice cream, salt is mixed with the ice surrounding the system to lower its temperature and aid in freezing the cream/sugar mixture.
Here is an easy way to make ice cream using salt and ice:
Check out my lab book "Chemistry on a Budget" at amazon.com:
Each lab is presented with two possible report formats -- both with the same procedure -- one with 10 questions to be answered as a conclusion, the other with a full laboratory report required. This was to give the teacher the option of what type of report is desired!
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Have a good end of the week!