Lab Assessment List

-Constructing the solubility curve for KCl

Possible Points

Points Earned

  1. Make a solubility graph for KCl which has:                             __22__
  1. Answers to questions (on back of this sheet)                         __18__
  2. Procedure (has all the steps)                                                    __10__
  3. Lab summary paragraph                                                           __10__

5. Lab participation                                                                             __5 ___

6. Presentation (neatness, spelling, grammar,                                 __5____

this list is stapled to front of papers)

QUESTIONS: (Answer these in full sentences. Make sure work is neat and spell-checked)

  1. Two compounds were used in this lab. What are their formulas? List the names of the elements that go into making them.
  2. What makes a compound different than a mixture?
  3. How is solubility measured? Is it a property that can be used to help you identify a substance?
  4. Was this lab a demonstration of chemical change? Read your book from 75-78 to see if making a solution of KCl and water represents a chemical reaction. Defend your answer with what you observed in the experiment?
  5. What are the three main factors that impact the solubility of a solute?
  6. Why did you have to stir the solution while cooling it? Why did you have to stir gently?
  7. KCl is what chemists categorize as a "salt". The container it comes in says that you should contact a physician if you accidentally ingest it. Yet, we eat "salt" every day. Why do you suppose KCl is called a "salt"?
  8. Explain why the KCl crystals form when the solution is cooled. Incorporate kinetic molecular theory into your answer.
  9. Use the graph you made of the averages from the classes to answer these questions:
    A) At 50 C, how much KCl can you dissolve into 100 mL of water?

B) If you had 400 mL of pure water that was boiling, how much KCl would you be able to dissolve into it?

C) What would you see happen if you stirred 50 g of KCl into a beaker of 100mL of water that was at a temperature of 10 C? Make sure your answer tells what you'll see before, during and after the mixing.

 10.   Compare a "saturated solution" to an "unsaturated solution".