Chemistry Topic 7

Properties of Solutions

• 2/2 Chemistry

• Properties of Solutions

• Aim: How do we describe solutions and their properties?

• Obj: SWBAT explain different parts of a solution and how different factors affect solubility

• Do Now: How can we refocus to succeed this semester?

• Homework: Memorize your Student ID numbers

• Solution = homogeneous mixture

• Ex Salt water NaCl(aq)

• Alloy = a solution of metals

Parts of a Solution

• Solute = the substance that is being dissolved

– There’s usually less of this

• Solvent = the substance that dissolves the solute.

•WATER SOLUTIONS ARE CALLED AQUEOUS SOLUTIONS AND THE NOTATION (aq) IS USED.

Solubility

• Materials that dissolve are said to be soluble

• Materials that don’t dissolve are said to be insoluble.

• LIKE

DISSOLVES

LIKE

Solubility

Solute Type

Nonpolar Solvent

Polar Solvent

Nonpolar Soluble Insoluble

Polar Insoluble Soluble

Ionic Insoluble Soluble

Like Dissolves Like

Temperature

• As temperature increases, most solids become more soluble in water.

• Gases are the opposite, as Temperature increases, the solubility of all gases in liquids decreases.

Pressure

• Pressure has little to no effect on the solubility of solids or liquids.

• As pressure increases, gases become more soluble.

• 2/3 Chemistry

• Properties of Solutions

• Aim: How do different substances differ in their solubilities?

• Obj: SWBAT interpret data to determine the concentration of solutions as well as recognize patterns in solubility

• Solubility show us how many grams of a solute can dissolve at various temperatures

• Reference Table G shows the solubility of substances at different temperatures in

100 g of water

• Unsaturated = when more of a solute can dissolve in the solvent

– Below the line

• Saturated = when the maximum amount of a solute is dissolved in the solvent

– On the line

– There is an EQUILIBRIUM between dissolving and falling out of solution

• Supersaturated = When more than the maximum amount of solute is dissolved in the solution

– Above the line

– Formed when you cool a saturated solution (slowly) and no crystals form

Recognizing Solution Saturation

• Unsaturated – If more solute is added, it will dissolve

• Saturated – There is already undissolved solute

– If more solute is added, it won’t dissolve and will fall to the bottom

• Supersaturated – If more solute is added, crystals will form and fall

out of solution.

• Workbook Problems

• 2/4 Chemistry

• Properties of Solutions

• Aim: How do we calculate solution concentrations?

• Obj: SWBAT calculate molarity and describe how this relates to the concept of moles

• Molarity (M) – the number of moles of solute in 1 L of solution

• 11.5 moles of CaCl2 are dissolved into 26.0 liters water. Find the molarity?

• Sea water contains roughly 28.0 g of NaCl per liter. What is the molarity of sodium chloride in sea water?

• How many moles of Na2CO3 are in 10.0 mL of a 2.0 M solution?

How many moles of NaCl are contained in 100.0 mL of a 0.20 M solution?

• Practice Problems

• 2/9 Chemistry

• Properties of Solutions

• Aim: How do we calculate percent by mass and volume and parts per million?

• Obj: SWBAT calculate percent composition and describe how this relates to the concept of solutions

• Homework: Worksheet

Percent by Mass

• What is the percent mass of sodium hydroxide if 2.50 g of NaOH are added to 50.00 g of H2O?

Percent by Volume

• What is the percent by volume of alcohol if 50.0 mL of ethanol is diluted with water to form a total volume of 300 mL?

Parts per Million

• Approximately 0.0043 g of oxygen can be dissolved in 100 mL of water at 20 oC. Express this in terms of parts per million.

• More Practice

• 2/10 Chemistry

• Properties of Solutions

• Aim: How do colligative properties affect solutions?

• Obj: SWBAT describe colligative properties and their effects on solutions, including how these properties are used everyday

• Homework: Finish Review packet (that means you’ll start it in class, so I don’t want to hear any, “but that’s homework” nonsense)

• Colligative Properties = properties that change based on the concentration of a solution

• Examples = Boiling Point Elevation, Freezing Point Depression

Ionic vs. Molecular

• Ionic compounds dissolve in water and separate into their ions. (electrolyte)

• Molecular compounds do not dissociate. (nonelectrolyte)

• Take into account the number of ions.

– More ions at the same Molarity = more concentrated = stronger colligative properties

• Freezing Point Depression – the more concentrated the solution, the lower the freezing point will be

• Boiling Point Elevation – the more concentrated the solution, the higher the boiling point will be

Colligative Properties

Vapor Pressure

• Vapor = gas phase of a substance that at room temp is solid or liquid

• The higher the vapor pressure, the weaker the intermolecular forces (Table H)

• Propanone has the weakest, ethanoic acid has the strongest

Boiling Point

• As temperature increases, so does vapor pressure

• Boiling point – when vapor pressure equals atmospheric pressure.

– This is why the boiling point of water is different at the top of a mountain.

• 2/11 Chemistry

• Properties of Solutions

• Aim: How do prepare for our exam

• Obj: SWBAT work through practice problems to deepen their understanding of the topic

• Homework: Study