Heats of solutions (ΔH) If given the choice, you’d prefer to receive from that someone special:...

Heats of solutions Heats of solutions ((ΔΔH)H)

If given the choice, you’d prefer to If given the choice, you’d prefer to receive from that someone special:receive from that someone special:

A) A dozen red rosesA) A dozen red roses B) A dozen pink rosesB) A dozen pink roses C) A nice plantC) A nice plant D) A nice floral arrangementD) A nice floral arrangement

What is meant by the term heat of What is meant by the term heat of solution?solution?

It is the It is the netnet amount of amount of heat energy absorbed heat energy absorbed

or released when a or released when a solute dissolves in a solute dissolves in a

solvent.solvent.

What tends to be a confusing part of What tends to be a confusing part of this topic is the frame of reference. this topic is the frame of reference. The frame of reference we use is the The frame of reference we use is the “solution system” (the beaker where “solution system” (the beaker where

the solution is prepared).the solution is prepared).

So, if after dissolving solute in So, if after dissolving solute in solvent, the beaker/solution is solvent, the beaker/solution is

warmer than the surroundings, heat warmer than the surroundings, heat will flow:will flow:

A) In (into the beaker from the surroundings)A) In (into the beaker from the surroundings) B) Out (out of the beaker into the surroundings)B) Out (out of the beaker into the surroundings)

When the solution warms up due When the solution warms up due to the dissolving process, we say to the dissolving process, we say

the process is:the process is: A) Endothermic (meaning heat flows into A) Endothermic (meaning heat flows into

the beaker from the surroundings)the beaker from the surroundings) B) Exothermic (meaning heat flows out of B) Exothermic (meaning heat flows out of

the beaker into the surroundings)the beaker into the surroundings)

Because heat will flow out of a Because heat will flow out of a

warm beaker, we call that a –warm beaker, we call that a –ΔΔHH.. It is defined as negative because It is defined as negative because

energy is going out of the energy is going out of the solution system.solution system.

How do we explain How do we explain the temperature the temperature

change? (Why does change? (Why does the temperature the temperature

change?)change?)

It is a function of three types of It is a function of three types of intermolecular interactions. Identify intermolecular interactions. Identify

the three types.the three types.

They are:They are:

Solute-soluteSolute-solute SolventSolvent--solventsolvent

SolSoluteute--solsolventvent

Which one(s) absorb energy?Which one(s) absorb energy? 1) 1) Solute-soluteSolute-solute 2) Solvent2) Solvent--solventsolvent 3) 3) SolSoluteute--solsolventvent A) 1A) 1 B) 2B) 2 C) 3C) 3 D) 1 & 2D) 1 & 2

Energy is required to overcome Energy is required to overcome solute-solute solute-solute

and and solventsolvent--solventsolvent

interactions.interactions.

When new When new solute-solute-solventsolventinteractions are formed, energy is interactions are formed, energy is

released.released.

The difference between the The difference between the energy required (or absorbed) to energy required (or absorbed) to

overcome intermolecular overcome intermolecular attractions and the energy attractions and the energy

released in the new attractions released in the new attractions determines the net heat of determines the net heat of

solution.solution.

If during the dissolution, more If during the dissolution, more energy is released than required, energy is released than required,

the solution will feel:the solution will feel:

A) WarmerA) Warmer B) CoolerB) Cooler

If during the dissolution, more If during the dissolution, more energy is required than released energy is required than released

the solution is considered:the solution is considered:

A) EndothermicA) Endothermic B) ExothermicB) Exothermic


the solution is defined to have a :the solution is defined to have a :

A) – A) – ΔΔH H B) + B) + ΔΔH H

If during the dissolution, more If during the dissolution, more energy is released than required, energy is released than required,



If during the dissolution, more If during the dissolution, more energy is released than required energy is released than required

the solution is defined to have a :the solution is defined to have a :

A) – A) – ΔΔH H B) + B) + ΔΔH H

If during the dissolution, more If during the dissolution, more energy is released than required energy is released than required

the solution is considered:the solution is considered:

A) EndothermicA) Endothermic B) ExothermicB) Exothermic

If a solution has a – If a solution has a – ΔΔH, the solution H, the solution will feel _________ when the solute will feel _________ when the solute

is dissolved. is dissolved.

A) warm A) warm B) cool B) cool

If more energy is released than If more energy is released than required when a solute it dissolved, , required when a solute it dissolved, ,

the solution will feel _________ the solution will feel _________ when the solute is dissolved. when the solute is dissolved.

A) warm A) warm B) cool B) cool

If more energy is released than If more energy is released than required when a solute it dissolved, , required when a solute it dissolved, ,

the solution will have a: the solution will have a:

A) + A) + ΔΔH H

B) – B) – ΔΔH H

When NaOH is When NaOH is dissolved, the solution dissolved, the solution

gets warmergets warmer

When NaNOWhen NaNO33 is is

dissolved, the solution dissolved, the solution gets coolergets cooler

When a solution is When a solution is formed, an energy formed, an energy

change occurs.change occurs.

When a solution gets When a solution gets warmer, energy is warmer, energy is being ________.being ________.

released into the released into the surrounding surrounding environmentenvironment

Because the “solution Because the “solution system” is releasing system” is releasing

(losing) energy, (losing) energy, we’ll say it has a –we’ll say it has a –ΔΔH, H,

a negative heat of a negative heat of solution.solution.

When a solution gets When a solution gets cooler, energy is cooler, energy is being ________.being ________.

absorbed from the absorbed from the surrounding surrounding environmentenvironment

Because the “solution Because the “solution system” is absorbing system” is absorbing

(gaining) energy, (gaining) energy, we’ll say it has a +we’ll say it has a +ΔΔH, H,

a positive heat of a positive heat of solution.solution.

Where is this energy Where is this energy change coming from?change coming from?

Consider the large salt Consider the large salt block. If it is placed block. If it is placed in a pool after some in a pool after some time it will _______.time it will _______.

When it dissolves, When it dissolves, what was a large salt what was a large salt

block is now tiny block is now tiny particles spread particles spread

throughout the water. throughout the water.

In order to change it In order to change it from a block of salt into from a block of salt into many small particles of many small particles of salt energy is _______.salt energy is _______. A) RequiredA) Required B) ReleasedB) Released

So the act of breaking So the act of breaking apart the solute apart the solute

requires energy and requires energy and will cool the water. will cool the water.

There are also There are also attractions/bonds attractions/bonds between one water between one water particle and another particle and another

that need to be that need to be broken/overcome. broken/overcome.

Then there are Then there are attractions/bonds attractions/bonds between the solute between the solute

and solvent particles. and solvent particles. These release energy.These release energy.

It (heat of solution) is It (heat of solution) is measured in kJ/molmeasured in kJ/mol

Acid + carbonate Acid + carbonate

COCO22 + H + H22O + “salt”O + “salt”

NaNa22COCO33 + MgBr + MgBr22

2 NaBr + MgCO2 NaBr + MgCO33

No acid involved hereNo acid involved here

HAPPY HAPPY BIRTHDAY BIRTHDAY REANNA!!REANNA!!

From,From,

CaraCara

4 things “drive” a reaction4 things “drive” a reaction

Make a precipitate Make a precipitate (insoluble substance)(insoluble substance)

Make a gas Make a gas Make water (HMake water (H22O)O)

Movement of electronsMovement of electrons

Matter can be classified Matter can be classified into two categoriesinto two categories

Matter

MixturesPure

Substances

MixturesMixtures can be broken can be broken into two categoriesinto two categories

Mixtures

Homogeneous Heterogeneous

Pure SubstancePure Substance can be can be broken into two categoriesbroken into two categories

Pure Substances

Elements Compounds

““MatterMatter” can be classified two ” can be classified two waysways

Pure substancesPure substances ElementsElements CompoundsCompounds

MixturesMixtures Uniform mixtures are Uniform mixtures are

called…called… HomogenousHomogenous Non-uniform Non-uniform

mixtures are called…mixtures are called… HeterogeneousHeterogeneous

Chunky peanut butter would be Chunky peanut butter would be considered a ________ mixture.considered a ________ mixture.

HeterogeneousHeterogeneousWhy?Why?It isn’t “uniform”. It’s partly It isn’t “uniform”. It’s partly

creamy (peanut butter), and creamy (peanut butter), and partly chunky (peanuts)partly chunky (peanuts)

Chunky peanut butter would also Chunky peanut butter would also be considered a ________be considered a ________

Good snack right now Good snack right now Put it on some toastPut it on some toastMmmmMmmmYou’d probably want some You’d probably want some

milk too eh?milk too eh?

An exampleAn example

If something is If something is solublesoluble it it means that itmeans that it

Can be dissolvedCan be dissolved

““Dissolution” is just a fancy Dissolution” is just a fancy word meaningword meaning

DissolvesDissolves

If something If something cannotcannot be be dissolved we say that dissolved we say that

substance is…substance is…

InInsolublesoluble

In a solution of water and In a solution of water and sodium nitrate, the water is sodium nitrate, the water is

called the…called the…““SolventSolvent”” The The sodium nitratesodium nitrate is called the… is called the…

““Solute” (sol-yute)Solute” (sol-yute)(Or in Sam’s case: sol-hjute)(Or in Sam’s case: sol-hjute)

In a solution of water and salt, In a solution of water and salt, the salt is called the…the salt is called the…

““Solute” (sol-yute)Solute” (sol-yute)The water is called the…The water is called the…

““Solvent”Solvent”

In a mixture, the In a mixture, the substances that make up substances that make up the mixture the mixture retain their retain their individual propertiesindividual properties

When mixtures are made, When mixtures are made, the properties of the the properties of the

mixture are a mixture are a combination combination of the properties of what of the properties of what

makes up the mixturemakes up the mixture

We discussed three types We discussed three types of “mixtures”:of “mixtures”:

SolutionsSolutions

ColloidsColloids

SuspensionsSuspensions

Mixtures that are made up Mixtures that are made up of very small particles are of very small particles are

called…called…

“ “Solutions”Solutions”

A solution is made up A solution is made up of a solute and a of a solute and a

solventsolvent

There are a wide There are a wide range of range of

solute-solvent solute-solvent combinationscombinations

Types of Types of solutionsolution combinations: combinations: Gas-gasGas-gas Gas-liquidGas-liquid Liquid-gasLiquid-gas Liquid-liquidLiquid-liquid Liquid-solidLiquid-solid Solid-liquidSolid-liquid Solid-solidSolid-solid

A word about alcoholA word about alcohol

Not all alcohols are Not all alcohols are consumableconsumable

The alcohol from grain The alcohol from grain is “ethyl alcohol”. is “ethyl alcohol”.

This can be consumedThis can be consumed

The alcohol from The alcohol from wood is “methyl wood is “methyl

alcohol”. This cannot alcohol”. This cannot be consumed.be consumed.

Rubbing alcohol is Rubbing alcohol is “isopropyl alcohol”. “isopropyl alcohol”.

This cannot be This cannot be consumed.consumed.

A solution is a mixture A solution is a mixture of two different of two different

substances that are substances that are evenly distributedevenly distributed

Particle diagramsParticle diagrams

Mixtures made up of a Mixtures made up of a little larger particles are little larger particles are

called colloidal dispersionscalled colloidal dispersions

a.k.a colloidsa.k.a colloids Colloids scatter light Colloids scatter light

(Tyndall effect)(Tyndall effect)

A “colloidal dispersion” A “colloidal dispersion” is also called a colloidis also called a colloid

A colloid consists of a A colloid consists of a dispersed phasedispersed phase (what (what there is less of) and a there is less of) and a dispersing medium dispersing medium

(what there is more of)(what there is more of)

Colloids Colloids appear appear homogeneoushomogeneous but are but are

actually heterogeneousactually heterogeneous

Types of Types of colloidcolloid combinations: combinations:

Gas dispersed in a liquidGas dispersed in a liquid Liquid dispersed in a gasLiquid dispersed in a gas Liquid dispersed in a liquidLiquid dispersed in a liquid Liquid dispersed in a solidLiquid dispersed in a solid Solid dispersed in a liquidSolid dispersed in a liquid Solid dispersed in a gasSolid dispersed in a gas Solid network dispersed in a liquidSolid network dispersed in a liquid

Identify these types of Identify these types of colloidcolloid combinations:combinations:

ExampleExample Dispersed Dispersed phasephase

Dispersing Dispersing mediummedium

PaintPaint

SmokeSmoke

AerosolAerosol

JelloJello




PaintPaint SolidSolid LiquidLiquid

SmokeSmoke SolidSolid GasGas

AerosolAerosol LiquidLiquid GasGas

JelloJello Solid networkSolid network liquidliquid




ButterButter

Whipped creamWhipped cream

MilkMilk




ButterButter LiquidLiquid SolidSolid

Whipped creamWhipped cream GasGas LiquidLiquid

MilkMilk LiquidLiquid LiquidLiquid

““suspensions” are…suspensions” are…

mixtures made up of mixtures made up of particles so large they must particles so large they must be stirred (agitated) to keep be stirred (agitated) to keep from falling to the bottomfrom falling to the bottom

A solution is made up of A solution is made up of particles that are very…particles that are very…

SmallSmall (less than 1 (less than 1 nanometer in size)nanometer in size)

Types of solute-solvent Types of solute-solvent combinationscombinations

If COIf CO22 is “dissolved in” O is “dissolved in” O2 2

this would be athis would be a

Gas solute (COGas solute (CO22) )

in a gas solvent (Oin a gas solvent (O22))

If COIf CO22 is dissolved in water is dissolved in water


Gas solute (COGas solute (CO22) )

in a liquid solvent in a liquid solvent (water)(water)

If sugar is dissolved in If sugar is dissolved in waterwater this would be athis would be a

Solid solute (sugar) Solid solute (sugar) in a liquid solvent in a liquid solvent (water)(water)

If water is dissolved in airIf water is dissolved in air


liquid solute (water) liquid solute (water) in a gas solvent (air) in a gas solvent (air)

If alcohol is dissolved in If alcohol is dissolved in waterwater this would be athis would be a

liquid solute (alcohol) liquid solute (alcohol) in a liquid solvent in a liquid solvent (water)(water)

An alloy is when two An alloy is when two metals are mixed. So this metals are mixed. So this

would be awould be asolid solute (tin) solid solute (tin) in a solid solvent in a solid solvent (copper) to make brass(copper) to make brass

Liquid solutions can be Liquid solutions can be classified as either classified as either

electrolytes or electrolytes or non-electrolytesnon-electrolytes

What does GatoradeWhat does Gatorade®® replenish?replenish?

ElectrolytesElectrolytesPrimarilyPrimarily Na Na++ and K and K++

““Electrolytes”Electrolytes” are substances which are substances whichDissolve in Dissolve in

waterwaterConduct Conduct

electricity electricity (current)(current)

““Non-electrolytes”Non-electrolytes” are substances are substances whichwhich

Dissolve in Dissolve in waterwater

Do not Do not conduct conduct electricity electricity (current)(current)

Electrolytes conduct electricity Electrolytes conduct electricity becausebecause

They form They form ionsions in water in water Examples:Examples: NaCl NaCl Na Na++ + Cl + Cl--

NaOH NaOH Na Na++ + OH + OH--

KK22SOSO44 2 K 2 K++ + SO + SO44--


They form They form ionsions in water in waterAnother word for this is they Another word for this is they

““dissociatedissociate”.”.

What does GatoradeWhat does Gatorade®® replenish?replenish?

ElectrolytesElectrolytesPrimarilyPrimarily Na Na++ and K and K++

Where do these sodium and Where do these sodium and potassium ions come from?potassium ions come from?

Sodium comes from NaClSodium comes from NaCl NaCl NaCl Na Na++ + Cl + Cl-- KK+ + comes from KHcomes from KH22POPO44

KHKH22POPO44 K K+++ H+ H22POPO44--

What really happens What really happens when a chemical when a chemical

dissolves in a liquid?dissolves in a liquid? Water molecules Water molecules surroundsurround

molecules of the solute molecules of the solute chemicalchemical

This process of the This process of the solvent breaking apart solvent breaking apart and surrounding the and surrounding the

solute is called solute is called “solvating”“solvating”

RatesRates of dissolution of dissolution(dissolving)(dissolving)

How fast something How fast something dissolvesdissolves

Three things can be done to make Three things can be done to make most solids dissolve faster:most solids dissolve faster:

Stir it (agitate)Stir it (agitate)Increase the surface area Increase the surface area

(make the particles smaller)(make the particles smaller)Heat up the solutionHeat up the solution

Why do each of these help to Why do each of these help to solvate the solute?solvate the solute?

They make the collisions They make the collisions between the solute and between the solute and solvent more frequent.solvent more frequent.

(i.e., bring fresh solvent into (i.e., bring fresh solvent into contact with the solute)contact with the solute)


They form They form ionsions in water in waterAnother word for this is they:Another word for this is they: “ “dissociatedissociate”.”.

What does KNOWhat does KNO33

dissociate into?dissociate into?

KK++ and NO and NO33--

What does KWhat does K22SOSO44


2K2K++ and SO and SO4422--

What does Mg(OH)What does Mg(OH)22


MgMg2+2+ and 2 OH and 2 OH--

Solutions that cannot hold Solutions that cannot hold any more solute are any more solute are

called…called…

“ “saturated” solutions”saturated” solutions”

Saturated solutions are in Saturated solutions are in equilibrium becauseequilibrium because

If some undissolved solute If some undissolved solute dissolves, then some already dissolves, then some already dissolved solute will dissolved solute will recrystalize. These processes recrystalize. These processes happen at the happen at the same same raterate..

Solutions that can hold Solutions that can hold more solute than they more solute than they

presently have are called…presently have are called…

““unsaturated” solutionsunsaturated” solutions

A “super-saturated” solution is A “super-saturated” solution is one that one that

Has dissolved more solute Has dissolved more solute than a similar solution would than a similar solution would under normal conditions.under normal conditions.

(They are very unstable) (They are very unstable)

A “super-saturated” solution is A “super-saturated” solution is made bymade by

Heating the solution up so Heating the solution up so you can get more solute to you can get more solute to dissolve in it, then letting it dissolve in it, then letting it cool.cool.

Molarity (M)Molarity (M) is a measure is a measure of a solution’s…of a solution’s…

ConcentrationConcentration

Which is more concentrated, a Which is more concentrated, a 1.40 M NaOH solution, or a 1.40 M NaOH solution, or a

0.55 M Na0.55 M Na22SOSO44 solution? solution?

The 1.40 M NaOH The 1.40 M NaOH solutionsolution

The formula for The formula for calculating Molarity (M)calculating Molarity (M)

is:is:

Moles of solute Liters of solution

Solubility of Solubility of gases gases as as it relates toit relates to pressure pressure

How is soda pop carbonated?How is soda pop carbonated?(How do they get the CO(How do they get the CO22 gas gas

in it?)in it?)They force it in by bottling it at They force it in by bottling it at

high pressurehigh pressure (5-10 (5-10 atmospheres of pressure) atmospheres of pressure)

So we can say that as the So we can say that as the pressure of a gas above the pressure of a gas above the

solution increases, the solubility solution increases, the solubility of the gas…of the gas…

IncreasesIncreases(more pressure means more gas (more pressure means more gas

will dissolve)will dissolve)This is known as…(whose law?) This is known as…(whose law?) ““Henry’s Law”Henry’s Law”

Gas solubility as it relates Gas solubility as it relates to to temperaturetemperature

Two cans of pop are opened. Two cans of pop are opened. One is placed in the One is placed in the fridgefridge;;

one is placed on the one is placed on the countercounter. .

Which can “goes flat” sooner Which can “goes flat” sooner and why?and why?

The one on the counter The one on the counter because the warmer the because the warmer the pop, the quicker it loses pop, the quicker it loses

it’s fizz (COit’s fizz (CO22 gas) gas)

So, as the So, as the temperaturetemperature of a of a solution goes up, the solution goes up, the

solubility of a gassolubility of a gas in that in that solution goes…solution goes…

Down. Down. Less gas will dissolve Less gas will dissolve in a warm solution than in a in a warm solution than in a cold solution.cold solution.

Ions that do not participate in a Ions that do not participate in a chemical reaction are called…chemical reaction are called…

Spectator ionsSpectator ions

A colligative property on one that A colligative property on one that depends on the _________, not depends on the _________, not

the _________the _________ConcentrationConcentrationNot the identity (so it makes Not the identity (so it makes

no difference if we’re talking no difference if we’re talking about sugar, salt, lithium about sugar, salt, lithium bromide….bromide….

Heats of solutions (ΔH) If given the choice, you’d prefer to receive from that someone special:...

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