Warm Up: Pg Work silently. Raise hand to ask Ms. Hughes anything.

1. Get a pink packet from the side shelves. 2. Do NOT write the question, only the answer.3. Do NOT write in the packet. Write on a SEPARATE

sheet. Label the warm up with the date.4. This is GEE practice so you must put an answer for

EVERY question even if it’s a guess. Leave NOTHING blank.

5. After time we will go over them.6. When finished, put the papers in the CORRECT order.

Announcements

• Unit 6 test this Friday (3/12)

• If you have not taken 5 chemistry tests yet this semester, see me after to arrange a make up

• Retake GLEs for GRADE BOOST

THIRD QUARTER END THIS FRIDAY!!!

Mystery Element

• Named for the sons of the Earth goddess in Greek mythology

• Very strong and very light

• Used in surgical pins and artificial hips

• 10,000lbs of it are used to make a Boeing 747

Take 1

Counting Eggs

• Often times instead of counting individual eggs we count them in groups of 12– 1 dozen = 12

– 3 dozen eggs OR 36 eggs

Counting Molecules: The Mole

• Instead of counting individual molecules we count groups of 6.022 x 1023.

– 1 mole = 6.022 x 1023

– 6.022 x 1023 = 602,200,000,000,000,000,000,000

Moles and Weight

• Because every compound is made of different atoms, every compound weighs a different amount.

• So, 1 mole of different compounds would also weigh a different amount.

What are solutions?

• Homogeneous mixture in which one substance dissolves in another.

• Parts of a solution:– Solute: the substance that dissolves

– Solvent: the substance that does the dissolving

How do solutes “dissolve”?

• Solvation: solvent particles pull apart and surround solute particles.

Observe the following solutions:

• If these solutions are made of the same solute and solvents, why do they look different?

Concentration

• Concentration measures the ratio of the number of molecules to the amount of solvent (usually water)

• If there are a lot of molecules in a little water the solution is concentrated

• If there are few molecules in a lot of water the solution is dilute

Molarity

• Molarity is the number of moles of solute in one liter of solution

• The unit for molarity is mol/L

V

molM

Molality

• Molality is the concentration of a solution expressed in moles of substance per kilogram of a solvent

• The unit for molality is mol/kg

kg

molm

Normality

• Normality is the concentration of a solution expressed in gram equivalents of solute per liter of solution

Molarity Example Problem

• You have 3.50L of a solution that contains 40 mol of sodium chloride (NaCl). What is the molarity of that solution?

Molality Example Problem

• A solution was prepared by dissolving 20 mol of sucrose (C12H22O11) in 125 g of water. Find the molal concentration of this solution.

Normality Example Problem

• A solution was prepared by dissolving 10 mol of Li2O in 4 L of H2O. What is the normality with respect to the Li+ ion?

Salt, Pasta Water, and Snow

• Anyone ever been told to add salt to boiling water so the pasta will cook faster?– Does this actually work?

• Why do northern cities own trucks whose job it is to pour salt on the roads when it snows?

Solubility and Ionization

• Like dissolves Like– Polar solutes dissolve in polar solvents– Ionic solutes are polar

• When an ionic solute dissolves, it breaks into its ions– This is called ionization– NaCl dissolves into 2 particles– CaCl2 dissolves into 3 particles– C12H22O11 dissolves into 1 particle (its not ionic)

BP and FP Changes

• A substance’s BP and FP change when something is dissolved– The ions hold onto the liquid particles tightly

• Answer the following questions. Explain your answer in a complete sentence

– If the ions are holding on the water particles more tightly, will it be harder or easier to boil the water? Will the Boiling Point be higher or lower?

– If the ions are holding on the water particles more tightly, will it be harder or easier to freeze the water? Will the Freezing Point be higher or lower?

Why?

• Explain, in complete sentences, why people add salt to water to make the pasta cook faster.

• Explain, in complete sentences, why salt is added to roads when it snows.

BP and FP Change Equation

kmiT Change in temperature

constant

molality

Number of dissolved particles

kg

molm

kb for water is 0.51 °C/m

kf for water is -1.86 °C/m

Why called “colligative” property?

• Colligative means it doesn’t matter what the solute is, only how much of it there is

An Example

• What is the boiling point of a 0.75 m MgF2 if water is the solvent?

Practice Questions

• Which of the following will increase the boiling point of solvent the most?– 1 m NaCl– 1 m C12H22O11

– 1 m CaCl2– 1 m Al2O3

– 1 m MgO

• What is the freezing point of a salt (NaCl) water solution with a molality of 3 m?

Question #1 Question #2

More Practice

• What is the molarity of a solution with 2.0 moles of CaCl2 in 4 L of H2O?

• What is the molality of a solution with 4.0 moles of CaCl2 in 6 L of H2O?

• What is the boiling point of a solution with 4 m CaCl2 in water?

Practice Quietly by yourself. Raise you hand if you have a question

Complete Concentration and Colligative Properties worksheet

Lab

• Read the directions carefully

• Listen for my call to rotate

• Rotate clockwise

• Always leave your station clean

• Do NOT leave your station until it’s time to rotate

Done Early?

• Start on homework

• Conferences

• Make up work– intermolecular forces worksheet and foldable– Retake or make up TESTS!!!

• Work quietly, be respectful

Sum up

• What did we learn today?

• HW: – Unfinished classwork

• Top Ten: – How’d we do?