Types of Solutions and Solubility Curves Mrs. Wilson Monday 4-18 and Tues 4-19 Types of Solutions and Solubility Curves Mrs. Wilson

Objectives Distinguish between solutions, colloids, and suspensions; electrolytes and non-electrolytes; and strong / weak electrolytes. Distinguish between solutions based on their degree of saturation: saturated, supersaturated, and unsaturated solutions. Interpret solubility curves for different ionic compounds to determine the degree of saturation of a solution. Homework: Colors of Chemistry Lab due next class. We’ll finish the lab questions next class.

Daily Quiz You do not need a calculator. You do need a periodic table.

Lesson 6.5: Types of Solutions A. Solutions, Colloids, Suspensions

Lesson 6.5: Types of Solutions A. Solutions, Colloids, Suspensions Tyndall effect: shown only in colloids – the colloidal particles are larger than the wavelength of the incident light, so that light beam “scatters” or broadens in width. Think of car headlights shining through fog.

Dissociation = separation of ions from each other Lesson 6.5: Types of Solutions B. Electrolytes vs. Nonelectrolytes; Weak vs. Strong Electrolytes Dissociation = separation of ions from each other All three solutions have complete dissolution (solute is completely dissolved) ~100% dissociation 0% dissociation Ex: Sugar water Ex: Vinegar, ammonia Ex: HCl, salt water

DEMO and VIDEO Water, Gatorade, Monster Any of you have drinks you want to test?  (You can’t drink them afterwards, obviously…)

Lesson 6. 5: Types of Solutions C Lesson 6.5: Types of Solutions C. Saturated, Unsaturated and Supersaturated Solutions Unsaturated = contains less than the max. mass of solute that could possibly dissolve in 100 g of H2O at a given temperature. Saturated = contains the max. mass of solute that can dissolve in 100 g H2O at a given temp. **As long as that temp. remains constant, any extra solid solute will be undissolved at the bottom of the saturated solution. ** The only factor that can change the solubility of a solute is temperature and pressure (for gaseous solutes only). To make a saturated solution, unsaturated, heat the solution!

VIDEO Unsaturated, Saturated and Supersaturated Project

Lesson 6. 5: Types of Solutions C Lesson 6.5: Types of Solutions C. Saturated, Unsaturated and Supersaturated Solutions Supersaturated = contains more than the max. mass of solute that solution can normally dissolve Make a saturated solution (w/ undissolved solute at the bottom) Heat the mixture to dissolve the solute (now it’s unsaturated) Cool the mixture EXTREMELY SLOWLY. Now it’s supersaturated. This system is unstable – any disturbance or the addition of a “seed crystal” will trigger crystallization to re-form a saturated solution.

QUICK LAB and VIDEO There are three setups. Crystallization There are three setups. Perform a test to see if the two test tubes contain an unsaturated, saturated or supersaturated solution. Obtain a test tube that contains a warmed solution. Perform a test to see if this test tube contains an unsaturated, saturated or supersaturated solution. Return this test tube to the hot water bath.

Lesson 6. 5: Types of Solutions C Lesson 6.5: Types of Solutions C. Saturated, Unsaturated and Supersaturated Solutions Another way to distinguish degrees of saturation is to consult a solubility curve. Supersaturated Unsaturated

Any point on a line represents a saturated solution. Example At 90oC, 40 g of NaCl(s) in 100g H2O(l) represent a saturated solution. Any point below a line represents an unsaturated solution. Example At 90oC, 30 g of NaCl(s) in 100g H2O(l) represent an unsaturated solution. 10 g of NaCl(s) has to be added to make the solution saturated.

Any point above a line represents a supersaturated solution. Example At 90oC, 50 g of NaCl(s) in 100g H2O(l) represent a supersaturated solution. Eventually, 10 g of NaCl(s) will crystallize; the liquid above the crystals will be saturated. Any solution can be made saturated, unsaturated, or supersaturated by changing the temperature. For solid solutes, when T increases, solubility increases. For gaseous solutes, when T decreases, solubility increases.

(answers to these questions and the homework is online)

Let’s go over the test…