Chapter 17Water and Aqueous Systems

• Liquid Water and Its Properties

• Water Vapor and Ice

• Aqueous Solutions

• Heterogeneous Systems

Water

• Make a list of everything you know about water:

Why is this going to hurt?

Ch 17.1 Liquid Water and Its Properties

• The Water Molecule

• Surface Properties

• Specific Heat Capacity

The Water Molecule

• H2O

• Triatomic

• O-H Polar Covalent Bond

• Oxygen highly electronegative, therefore acquires the slightly negative charge

• Bond Angle of 105o

• Dipole forces of attraction

Properties due to Hydrogen Bonding

• High Surface Tension

• Low Vapor Pressure

• High Specific Heat Capacity

• High Heat of Vaporization

• High Boiling Point

Surface Tension

• Molecules in a liquid are pulled in all directions due to intermolecular forces

• The molecules at the top are only pulled down and to the sides, they are not pulled up. – These molecules tend to tighten up the top

Surfactant

• A wetting agent that decreases surface tension of water, soap

Low Vapor Pressure

• Hydrogen Bonds hold water molecules together preventing them from entering the vapor phase

Specific Heat Capacity

• 4.18J (1 cal) to raise 1g of water 1oC

• High due to hydrogen bonding

Water in Space

• http://video.google.com/videoplay?docid=-5089084492638545730

• http://video.google.com/videoplay?docid=243028165368764588&q=water+in+space&total=3270&start=0&num=10&so=0&type=search&plindex=9

• http://video.google.com/videoplay?docid=5098206590977878321&q=water+in+space&total=3270&start=10&num=10&so=0&type=search&plindex=1

Chapter 17.2 Water Vapor and Ice

• Evaporation and Condensation

• Ice

Evaporation

• Heat of Vaporization - 2.26kJ of energy is needed to convert 1g of water at 100oC to 1g of steam at 100oC (on your reference table)

• How much energy in kJ is required to change 52.3g of water at 100oC to steam at 100oC?

Condensation

• 2.26kJ is given off when 1g of steam at 100oC is converted to 1g of water at 100oC

• How much energy in kJ is given off to change 12.4g of steam at 100oC to water at 100oC?

Ice

• As water cools it behave like most liquids and its density increases.

• Once it cools to 4oC, it decreases in density.

• Ice has about a 10% greater volume than water.

• Ice has a lower density than water, therefore it floats.

Why does ice float?

Heat of Fusion

• 334J of energy is needed to convert 1g of ice at 0oC to 1g of water at 0oC (on your reference table)

• How much energy in kJ is required to change 21.8g of ice at 0oC to water at 0oC?

Ch 17.3 Aqueous Solutions

• Solvents and Solutes

• The Solution Process

• Electrolytes and Nonelectrolytes

• Water of Hydration

Aqueous Solutions

• Water with dissolved samples in it

Solvents

• The dissolving medium

Solutes

• The dissolved particles

Name the Solvent and Solute

• Kool Aid

Name the Solvent and Solute

• Hot Chocolate

Name the Solvent and Solute

• Salt Water

Name the Solvent and Solute

• Tea

Solution Process in Three Steps

• Step 1 – Separation of solvent molecules, requires energy to break intermolecular forces (ΔH1)

• Step 2 – Separation of solute molecules, requires energy to break intermolecular forces (ΔH2)

• Step 3 – Solvent and Solute Molecules Mix, may be exothermic or endothermic (ΔH3)

Heat of Solution ΔHsoln

• ΔHsoln = ΔH1 + ΔH2 + ΔH3

• ΔHsoln < 0 , exothermic, solution process is favorable

• ΔHsoln > 0 , endothermic, solution process is not favorable

Electrolytes

• Compounds that conduct an electrical current in an aqueous solution or molten state

• All ionic compounds are electrolytes• Barium sulfate conducts electricity in the

molten state but not in the aqueous state, WHY?

• Insoluble in water

Nonelectrolytes

• Compounds that do not conduct an electrical current in an aqueous solution of molten state

Weak Electrolytes

• When in solution, only a fraction of the solute exists as ions

Strong Electrolytes

• When in solution, most of the solute exists as ions

Strong Electrolytes

Weak Electrolytes

Non-Electrolytes

ACIDS(Inorganic)

HCl

HBr

HI

HNO3

H2SO4

HClO4

BASES(Inorganic)

NaOH

KOH

Soluble Salts KCl

MgSO4

KClO3

Heavy Metal Halides HgCl2

PbCl2

Bases(Inorganic)

NH3

Acids (Organic)

Acetic Acid

Bases (Organic)

aniline

H2O

Most Organic Compounds

Glucose

Glycerol

Water of Hydration (Crystallization)

• The water molecules that make up part of a crystal

• A compound that contains water of hydration is called a hydrate

Copper(II) Sulfate Pentahydrate – Deep Blue Crystals

Ch 17.4 HeterogeneousAqueous Systems

• Suspensions

• Colloids

Suspensions

• Mixtures from which particles settle out upon standing

• The particles are much larger than that of a solution

• Heterogeneous

• Particles larger than 100nm

• Can be filtered

Colloid

• Heterogeneous mixtures containing particles that are intermediate in size between suspensions and solutions

• Size between 1nm and 100nm• Glue, Jell-O, paint, smoke• Cloudy or milky in appearance when

concentrated• Clear or almost clear when they are dilute

Tyndall Effect

• Scattering of visible light in all directions

• Suspensions can exhibit the Tyndall Effect, solutions never do

Brownian Motion

• Chaotic movement of colloidal particles

• Caused by collisions between water particles and small dispersed colloidal particles

• These collisions prevent the particles from settling

Emulsions

• Colloidal dispersions of liquids in liquids

• Example: Oil and water mixed together with soap