1. Molality, Colloids, Suspensions

2. Evaluation/Assessment:
Objective:
Today I will be able to:
Explain why suspensions and colloids are not solutions
Calculate the concentration of a solution using the equation for molality and mole fractions
Evaluation/Assessment:
Informal assessment – monitoring student progress as they complete the practice
Formal assessment – analyzing student responses to the classwork and exit ticket.
Common Core Connection
Build Strong Content Knowledge
Make sense of problem and persevere in solving them
Look for and express regularity in repeated reasoning

3. Lesson Sequence Evaluate: Warm – Up
Explain: Molality, Suspensions and Colloid Notes
Elaborate: Molality Calculations
Explain: Mole Fraction
Elaborate: Mole Fraction Calculations
Evaluate: Exit Ticket

4. Warm - Up What is the proper lab technique for preparing a solution?
What is the difference between an unsaturated, saturated and supersaturated solution?

5. Objective Today I will be able to:
Explain why suspensions and colloids are not solutions
Calculate the concentration of a solution using the equation for molality

6. Homework Finish Molality/Mole Fraction Calculations
Wear closed toe shoes Friday for Dilutions lab

7. Agenda Warm-Up Molality, Suspensions and Colloids Notes
Molality Calculations
Mole Fraction Notes
Mole Fraction Calculations
Exit Ticket

8. Molality, Suspensions and Colloids Notes

9. Molality (m) = moles of solute/kg of solvent
Molality is used for vapor pressure and temperature change
Used because it does not change with change in temperature

10. Things that Remind Mr. Klotz of Solutions (but are not)
Suspension - a mixture from which some particles will slowly settle when left alone for a period of time (muddy water)
- Particles that settle can be filtered out

11. Things that Remind Mr. Klotz of Solutions (but are not)
Colloid – heterogeneous mixture of two or more substances that appears to be a solution
Smoke (solid in gas), marshmallow (gas in a solid), whipped cream (gas in a liquid)

12. Things that Remind Mr. Klotz of Solutions (but are not)
Tyndal Effect – allows you to distinguish between a true solution and a colloid
Shine a light on a true solution, and the light is invisible
Shine a light on a colloid, and you will be able to see the light beam as it reflects off the relatively large solute particles (headlights in fog)

15. Molality Calculations

16. Mole Fraction

17. Mole Fraction
Χi = moles of i
total moles

18. Mole Fraction Example
0.100 mole of NaCl is dissolved into grams of pure H2O. What is the mole fraction of NaCl?
Steps to solve the problem
Convert mass of H2O  moles of H20
Add the moles of H2O and NaCl together to get the total number of moles in the solution
Divide the moles of NaCl by the total number of moles
Answer: 0.982
No units because it is a ratio!

19. Mole Fraction Practice
Complete the practice at your desk. The problems you do not finish will become your homework.

20. Exit Ticket
How would you prepare 1.5 L a 2.0 M solution from a stock solution of 6.0M HCl?