Chapter 9(Page 269)

What is a solution?

Is vinegar a solution?

Is marble a solution?

Is milk a solution?

Solid copper sulfate(CuSO4)

Copper sulfate solution

In solution the copper ions (Cu2+) dissociate from the sulfate ions (SO42–)

A true solution is homogeneous on the molecular level

All solutions contain one solvent and at least one solute

dissolved: term used to describe when molecules of solute are completely separated from each other and dispersed into a solution.

• Solutions are important because most of the reactions in our body occur in solutions

• Air is a solution made up of different gasses• 14 carat gold is a solution made up of 14 out

of every 24 grams is gold (the other 10 grams is made up of silver)

• Some solutions are polar and others are molecular (ionic solutions conduct electricity and molecular do not)

• Wet skin is 1000 times more conductive than dry skin (this is why water should not be near electricity)

• A solution is made up of a solvent (the liquid or the most abundant amount) and the solute (the least abundant amount)

• When a solution is made, the solute normally is dissolved in the solvent

• Water is the universal solvent because it dissolves so many different compounds

• To dissolve means to totally disassociate the molecules of solute in the solvent

• Your body is about 60% water by weight• When you exercise, you can lose as much

as a half gallon of water which must be replaced or your body would stop working (this is why water is so important)

• Water is polar which means that it has a partially negative charged end of the molecule and a partially positive charged end

• Water also has what is called hydrogen bonding (a special type of intermolecular bonding)

Methane is a linear compound and does not contain hydrogen bonding like water

Water has hydrogen bonds and this produces the surface tension that can allow a pin to float on water, something that methanol cannot do

Water is a really good solvent that can dissolve other polar molecules

A really good solvent for organic compounds (non polar) is acetone and mineral spirits

There are different types of water which have different purposes Distilled water is water that is collected

specifically at 100oC and allowed to cool (the water is pure since that is the boiling point of water)

Deionized water is water that has had the ions removed (ions like Fe, Mg, Ca) that make water hard

Tap water is water that has been treated with chlorine, fluorine and may also have other ions like those found in the pipes that carry them

Water is called the universal solvent and there are symbols that come along with chemical reactions

Some of the symbols are: s – solid l – liquid g – gas aq – dissolved in water

There is a strong attraction among water molecules due to hydrogen bonding

Special case of water

Water is a small, polar molecule

Why are the boiling points so different?

WaterH2O

18 g/mole

MethaneCH4

16 g/mole

Boils at +100oC Boils at –161oC

Special case of water

WaterH2O

18 g/mole

MethaneCH4

16 g/mole

Boils at +100oC Boils at –161oC

Hydrogen bonding leads to interesting properties in water

polar nonpolar

Hydrogen bonds keep water molecules together, preventing them

from separating easily.

Without these strong intermolecular forces, methane

is a gas at room temperature

Special case of water

Hydrogen bonding leads to interesting properties in water

Substances are generally denser in the solid phase than in the liquid phase.

Water is different

In ice, hydrogen bonds force water molecules to align in a crystal structure where molecules are farther apart than they are in a liquid.

Why ice floats in water

Special case of water

Water as a solvent

hydration: the process of molecules with any charge separation to collect water molecules around them.

Not chemically bonded

Are there different “kinds” of water?

Tap water

Deionized water

Distilled water

Tap water contains dissolved salts and minerals.

Distilled water and deionized water have been processed to remove dissolved salts and minerals.

Deionization is a specific filtration process to remove all ions.

Distillation boils water to steam which is then condensed back to liquid water

In general,“like” dissolves

“like”

Polar solvents dissolve polar solutes

Nonpolar solvents dissolve nonpolar solutes

Not everything dissolves in water. Why not?

Take a new sheet of paper and fold it into three sections

Write your name, the title of the chapter and the number

On the first section from the sheet of paper, please write six things that you learned from your notes so far that could appear on your test.

In order for many chemical reactions to occur they must be in aqueous form (in water)

Solids are close together, but they are low in energy and cannot react as quickly

Gases are full of energy, but they are so few and far between so even though they have the energy to react, they must literally touch each other to react and bond

The life of all living organisms involve the chemical reactions that occur in aqueous settings

Least common state of matter!

Liquids exist only in a narrow range of temperatures and pressures

Definite volume Takes shape of container Particles in constant motion Particles closer together than a gas Greater attraction between molecules

than in a gas Caused by Dipole-dipole and London

dispersion forces

More ordered than gases Not bound in fixed positions Called fluids A substance that can flow and therefore

take the shape of its container Relative high density Relative incompressibility Ability to diffuse

Surface tension - A force that tends to pull adjacent parts of a liquids surface together.

Capillary action - The attraction of the surface of a liquid to the surface of a solid.

Vaporization- Changing a liquid or solid to a gas

Evaporation - When particles escape and non-boiling liquid and enter the gas state

Write a $3.00 summary on what you have learned using 4 of the vocabulary words used in this section

Complete the questions 1-11 on page 290

Honors Chemistry Homework Page 291 # 28 - 35

Solubility Molarity Saturated Aqueous equilibrium Supersaturated

Concentration

More solute Less solute

How can we express concentration quantitatively (with numbers)?

In a healthy person, potassium is dissolved in blood at a concentration of 140 to 200 mg/L.

If the concentration is less than 130 mg/L: muscle weakness and heart rhythm instability (hypokalemia)

If the concentration is higher than 215 mg/L: heart instability (hyperkalemia)

Concentration

The concentration is expressed as the mass of potassium per volume unit of blood

The concentration of a solution describes how much of a solute (the solid or least amount) is dissolved in the solvent (the liquid or the one that is the most abundant)

A solution is concentrated when there is a lot of solute in the liquid

A solution is dilute when there is a little amount of solute in the liquid

Some solutes can dissolve more than others and that describes solubility

Temperature and solubility

You can dissolve (a lot) more sugar at higher temperatures

Temperature and solubility

For other solutes, solubility changes very little with temperature

There are three different types of concentrations: Percent using grams of solute per liter of

solution Percent using mass of solute to divided by

mass of solution Moles of solute per liter of solution (molarity)

Temperature affects:

- the solubility of solutes how much

- the rate of solubility how fast

Calculate the molarity of a salt solution made by adding 6.0 g of NaCl to 100 mL of distilled water.

Concentration

Asked: Molarity of solution

Given: Volume of solution = 100.0 mL, mass of solute (NaCl) = 6.0 g

Relationships:

22.99 35.45 58.44 /

1,000 1.0 , 100 0.10

molesM

L

Formula mass of NaCl g mole

mL L therefore mL L

Dissolving rate

Substances are often ground up into powder to make them dissolve faster

A 1 cm cube has a surface area of 6 cm2

The same volume has a surface area of 9 cm2 when

divided up into smaller cubes

Preparing a solution

1. Determine the formula mass of the solute.

2. Use the formula mass of the solute to determine the grams of solute needed.

3. Weigh the grams of solute on the balance.

4. Add the solute to a volumetric flask or graduated cylinder.

5. Fill the flask about two thirds of the way up with distilled water.

6. Mix the solution until the solid dissolves completely.

7. Fill the volumetric flask or graduated cylinder up to the correct volume marker.

How to prepare a 500.0 mL solution of a 1.0 M CaCl2 solution.

Definite shape Definite volume Definite melting point - temp

at which a solid become a liquid

crystals have a definite mp

A solution is said to be saturated when it has as much solute as is possible to be dissolved (if anymore is added, it does not dissolve)

At the saturation point, there is a dynamic (active) aqueous equilibrium that is seen (the amount of dissolved solute is equal to the amount of solute becoming un-dissolved)

Solutions can sometimes be forced to dissolve more solute than normal - this is done by first dissolving the solute then raising the temperature, dissolving more, then slowly lowering the temperature back to the desired temp ( at the new final lower temperature, there would be more solute dissolved than if the temperature was not raised before adding solute)

An example of this is water at freezing point can dissolve 177g sugar / ml of water and at 90oC the amount that can be dissolved has more than doubled to 410g sugar / ml of water

This process is used in the making of rock candy and sodas (with sodas, the pressure instead of the temperature is used)

Many salts cannot be forced to dissolve more in water, regardless of the temperature (sodium chloride is a good example at 20oC its solubility is 26.4 % and at 70oC it only rises to just over 27 %)

In water oxygen can dissolve more in cold water than in warm water (so in the ocean, there is more oxygen in the deep than in the shallow water

To prepare a solution of known molarity you: Find the formula mass of the solute Determine the number of moles needed and

multiply it by the formula mass of the solute Weigh the grams of solute on a balance Full a volumetric flask 2/3 full with solvent

then add and mix solute well Completely fill the flask to the correct volume

mark (use an eye dropper to be more accurate)

Prepare 500 ml of a 1.0 M CaCl2 solution

Formula Molarity = moles / Liters

Moles = 40.078 + (2 x 35.5) = 110.98

So dissolve 110 g in a total of 1L water to get 1 M Or 55.49 g in 500mL solution of water

Two type of solids:Crystalline Solids - arranged in an orderly, geometric, repeating pattern.

• salt, sugar, ammethyst ,calciteAmorphous Solids particles are arranged in a random pattern

glass, plastics

Crystal structure- the total three dimensional arrangement of particles of a crystal.

Unit cell- smallest portion of a crystal lattice that shows the three-dimensional pattern of the entire lattice.

On the second section of that sheet of paper, please write six things that you learned from your notes so far that could appear on your test.

Positive and negative ions Group 1 & 2 combine with group 16 & 17 Hard Brittle High MP Good Insulators

Contain single atoms Each is covalently bonded to the next Diamond, quartz, silicon carbide Tend to be giant molecules Very hard and brittle High melting points Non-conductors or semiconductors

Consist of metal atoms surrounded by a sea of electrons.

High electrical conductivity Melting points vary greatly

Covalently bonded molecules Held together by intermolecular forces If nonpolar- London dispersion If polar- by dispersion, dipole-dipole and

hydrogen bonding Low melting points Easily vaporized, relatively soft, good

insulators

amorphous solids have no definite mp -- instead become thick sticky liquids.

Super-cooling High density-- generally

solids have their greatest density

Antimony and bismuth are less dense in solid than a liquid.

Water is less dense as solid Density of water = 1 g/cm3

Write a $3.00 summary on what you have learned using 4 of the vocabulary words used in this section

Complete the questions 12-19 on page 290

Honors Chemistry Homework: Page 291 # 43 - 48

Heat of solution Enthalpy Colligative properties Entropy Molality Electrolyte Volatile

Which acid will dissolve the limestone fastest?

Reaction rates

Higher temperature generally means a faster reaction rate

Reaction rates

In many cases, the amount of solute (concentration) can change the rate (speed) in which the reaction can occur

A 2 M solution can increase the rate of a reaction twice than of a 1 M solution because there are more particles that can take part in the reaction process

In digestion, increasing the surface area of the food exposes more of the food to the digestive juices, thus speeding up the digestion process

Other things that can increase the rate of a reaction are sometimes, temperature, pressure, and surface area) depending on the type of reactions

To summarize the facts, a higher concentration or temperature generally increases the reaction rate

When a solute dissolves in water, interparticulate bonds are broken and hydrogen bonds may form between water and the solute molecules and energy may be gained or lost in the process

The energy gained or released when bonds are broken when a solute dissolves in a solution is called heat of solution

When calcium chloride dissolves in water, it gives off heat to the surroundings (an increase of temperature) and is called an exothermic reaction – used in heat packs

When ammonium nitrate dissolves in water it absorbs heat from the surroundings and the temperature drops and is called an endothermic reaction – used in cold packs

The heat that is involved in a chemical reaction is called enthalpy

Enthalpy is negative in an exothermic reaction since the reaction gives off energy to the surroundings

Enthalpy is positive in an endothermic reaction since the reaction absorbs energy from the surroundings

A calorimeter is a device used to calculate the amount of heat gained or lost in a chemical reaction

In simple labs, a coffee-cup calorimeter is used since Styrofoam is generally a good insulator and keeps heat inside the container (good for reactions like ionic salts dissolving in water, neutralization reactions between acids and bases, and oxidation-reduction reactions between metals and acids

The heat comes from calcium chloride dissolving

In an exothermic process, energy is released

In an endothermic process, energy is absorbed

The cooling effect comes from ammonium nitrate absorbing heat as it dissolves

heat of solution: the energy absorbed or released when a solution dissolves in a particular solvent.

Energy released

Energy absorbed

Change of heat in a solution (∆H) = (grams of solution) X (specific heat of solution) X Change in Temperature (∆T)

Or

Change of Heat of solution (∆H solution)

= - change of heat in the reaction (∆H reaction)

Calorimetry

A coffee cup calorimeter is an isolated system

Calori-metry

“heat” “measure”

thermometer

Remember: Heat and temperature are related

If we can calculate ∆Hsolution, we can determine ∆Hreaction

qsolution = (grams of solution) x (specific heat of solution) x ΔT

qsolution = –qreaction

ΔHreaction = qreaction / moles

qsolution = (grams of solution) x (specific heat of solution) x ΔT

qsolution = –qreaction

ΔHreaction = qreaction / moles

4.18p o

JC water

g C

Seen in Chapter 3.2

Relationships:

Solve: First note that the temperature increased, so the reaction released energy to the solution. This means the reaction is exothermic and will have a negative H. Total volume of solution is 40.0 mL + 40.0 mL = 80.0 mLTotal mass of solution is 80.0 g using the densitywater (1.0 g/mL).

The positive sign indicates heat is absorbed.We reverse the sign as heat gained by the solution is lost by the reaction. Therefore qrxn = –1.67 kJ.

solution solution p solutionq m C T

80.0 4.18 27.0 22.0

1,672 1.67

o o o

solution

solutionq g J g C

kJq J

C C

What we have seen so far…

Reaction rates increase with:

increasing concentrations

increasing temperatures

Chemical reactions are accompanied by changes in enthalpy, ΔH

,

#

reaction solution solution p solution

reactionreaction

q q m C T

qH

of moles

,

#

reaction solution solution p solution

reactionreaction

q q m C T

qH

of moles

Volumes of solute and solvent do not add up to the volume of solution

20 g salt

80 mL water

87 mL solution!

Salt dissociates into ions, which fit in between water molecules

Solution vs. pure solvent

The density of a solution increases as more solute is added

Solution vs. pure solvent

When solutes are added to water it changes the density of water (for example, salt water is more dense than fresh water)

Almost all solute increases the density of water The density of diet soda is less than that of

water so it floats while regular sodas sink because they have over 40 g of sugar added that makes them more dense than regular water

When salt is added to water, the freezing point of water lowers (this is why it is used on the roads before a snow storm in the winter)

Also, adding salt to water raises the boiling point

Colligative properties are those properties that do not change based on the nature or type of particle such as freezing point depression

For dilute solutions there is a direct relationship between the increase in the number of solute particles and the decrease in the solution’s freezing point

In order for a solution to freeze it must have a structured arraignment of its particles

Entropy “S” is the amount of randomness in a system so when a substance freezes, it entropy decreases and when a substance becomes a liquid or a gas the entropy increases (since the particles are less organized)

When scientist want to calculate the change in freezing point based on the concentration of a solute, a new unit of concentration must be used that does not involve temperature or volume like molarity, this new unit is called molality

Molality is the number of moles of solute per kilograms of solvent

When liquids are heated their volume can change this is why molarity cannot be used to accurately calculate the change in freezing point

Freezing point depression

Why does ice melt when salt is sprinkled on it?

Pure water freezes at 0oC, but a water and salt solution freezes at a lower temperature.

Electrolyte solutions

Aqueous solutions containing dissolved ions are able to conduct electricity

1 mole of solute → 2 moles of ions

1 mole of solute → 3 moles of ions

The greater the number of particles in solution, the greater the effects.

colligative property: physical property of a solution that depends only on the number of dissolved solute particles not on the type (or nature) of the particle itself.

colligative property: physical property of a solution that depends only on the number of dissolved solute particles not on the type (or nature) of the particle itself.

Pure solventSolid formation is not hindered

SolutionSolute particles “get in the way” of solid formation

Ord

er

En

tro

py

more

less more

less

Freezing point depression is a

colligative property

To calculate the freezing point of a solution:

Do not get confused with molarity, M (moles solute / L of solution)

Two practical properties of colligative properties are: Antifreeze Deicer

Calculate the freezing point of a 1.8 m aqueous solution of antifreeze which contains ethylene glycol (C2H6O2) as the solute.

Calculate the freezing point of a 1.8 m aqueous solution of antifreeze that contains ethylene glycol (C2H6O2) as the solute.

Asked: The freezing point of a 1.8 m solution of ethylene glycol

Given: Molality = 1.8 m; Kf = 1.86oC/m (for water the solvent)

Relationships:

Solve:

Answer: The freezing point is lowered by 3.35oC.

f fT K m

1.86 1.8 3.3

3.

5

30 3.35 5

o of

o

f

o oFreezing point of antifreeze solution

T K m C m m

C C

C

C

On the third section from that sheet of paper, please write six more things that you learned from your notes so far that could appear on your test.

Equilibrium - dynamic condition in which two opposing physical or chemical changes occur at equal rates in a given closed (constant mass ) system

System Phase Condensation Concentration

When a physical or chemical system at equilibrium is disturbed by application of a stress (such as a change in concentration, pressure, or temperature), it attain a new equilibrium position that minimizes the stress.

The pressure exerted by the molecules of a vapor which are in equilibrium with its corresponding liquid at a given temperature

Water can be a liquid up to 374.10C See next slide

Triple point- indicates the temperature and pressure at which the solid, liquid, and vapor of the substance can coexist.

Critical temperature- the temperature above which the substance cannot exist in the liquid state

On the first section from the back page of that sheet of paper, please write six more things that you learned from your notes so far that could appear on your test.

Volatile- liquids that evaporate readily ether perfume acetone

Structure OH H

1050

sp3 hybrid bonds for the O-H

H---O very polar

Molecule is polar

Write a $3.00 summary on what you have learned using 4 of the vocabulary words used in this section

Complete the questions 20-27 on page 256

Complete questions 56 – 60 on page 256

Honors Chemistry Homework Page 256 # 56 - 60

Homework requirement: Learn all terms and concepts covered on this topic.

Make sure you have all assignments between page 890 and 293 completed and turned in by your test date.