Water and Its Properties > Chapter 15: Water and Aqueous Systems 15.1 Water and its Properties.

Water and Its Properties >

Chapter 15: Chapter 15: Water and Water and

Aqueous SystemsAqueous Systems15.1 Water and 15.1 Water and its Propertiesits Properties


Water in the Liquid StateWater in the Liquid StateA water molecule is polar.A water molecule is polar.

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Water in the Liquid StateWater in the Liquid State Polar molecules are attracted to Polar molecules are attracted to

one another by dipole one another by dipole interactions. The negative end of interactions. The negative end of one molecule attracts the one molecule attracts the positive end of another molecule.positive end of another molecule.

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Water in the Liquid StateWater in the Liquid State The The

intermoleculintermolecular attraction ar attraction among water among water molecules molecules results in the results in the formation of formation of hydrogen hydrogen bonds.bonds.

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Water in the Liquid StateWater in the Liquid State

Many unique and important Many unique and important properties of water—properties of water—including its high surface including its high surface tension and low vapor tension and low vapor pressure—result from pressure—result from hydrogen bonding.hydrogen bonding.

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Surface TensionSurface TensionThe inward force, or pull, The inward force, or pull, that tends to minimize the that tends to minimize the surface area of a liquid is surface area of a liquid is called called surface tension.surface tension.

All liquids have a surface All liquids have a surface tension, but water’s surface tension, but water’s surface tension is higher than most.tension is higher than most.

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A A surfactantsurfactant is any is any substance that interferes substance that interferes with the hydrogen with the hydrogen bonding between water bonding between water molecules and thereby molecules and thereby reduces surface tension.reduces surface tension.

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Capillary ActionCapillary Actionattractive force between the surface attractive force between the surface

of a liquid and the surface of a solidof a liquid and the surface of a solid

water mercury


Water in the Liquid StateWater in the Liquid State Vapor PressureVapor Pressure

Hydrogen bonding between water Hydrogen bonding between water molecules also explains water’s molecules also explains water’s unusually low vapor pressure. unusually low vapor pressure. Because hydrogen bonds hold water Because hydrogen bonds hold water molecules to one another, the molecules to one another, the tendency of these molecules to escape tendency of these molecules to escape is low, and evaporation is slow.is low, and evaporation is slow.

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Water in the Solid StateWater in the Solid State

As water begins to cool, it As water begins to cool, it behaves initially like a typical behaves initially like a typical liquid. It contracts slightly liquid. It contracts slightly and its density gradually and its density gradually increases. When the increases. When the temperature of the water temperature of the water falls below 4˚C, the density falls below 4˚C, the density of water starts to decrease.of water starts to decrease.

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Water in the Solid StateWater in the Solid State

The structure of ice is a regular The structure of ice is a regular open framework of water molecules open framework of water molecules arranged like a honeycomb.arranged like a honeycomb.

When ice melts, the framework When ice melts, the framework collapses, and the water collapses, and the water molecules pack closer together, molecules pack closer together, making liquid water more dense making liquid water more dense than ice.than ice.

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1.1. Many of the unusual Many of the unusual properties of water are the properties of water are the result of result of

a) hydrogen bonding.a) hydrogen bonding.

b) nonpolar molecules.b) nonpolar molecules.

c) low molar mass.c) low molar mass.

d) dispersion forces.d) dispersion forces.

15.1 Section Quiz.15.1 Section Quiz.


2.2. A surfactant causes water to A surfactant causes water to spread out over a surface. This spread out over a surface. This spreading occurs because the spreading occurs because the surfactantsurfactant

a) attaches to the surface.a) attaches to the surface.

b) interferes with hydrogen b) interferes with hydrogen bonding.bonding.

c) lowers the vapor pressure.c) lowers the vapor pressure.

d) lowers the density of water.d) lowers the density of water.



3.3. Ice is less dense than liquid Ice is less dense than liquid water because in ice the water water because in ice the water molecules molecules a) expand because of weakened a) expand because of weakened covalent bonds.covalent bonds.b) have a regular open honeycomb b) have a regular open honeycomb framework.framework.c) expand because of weakened c) expand because of weakened hydrogen bonds.hydrogen bonds.d) have a more disorderly d) have a more disorderly arrangement with lower density.arrangement with lower density.



15.2 15.2 Homogeneous Homogeneous

Aqueous SystemsAqueous Systems

Water and Its Properties >15.2Solvents and Solvents and

SolutesSolutesAn An aqueous solutionaqueous solution is is water that contains water that contains dissolved substances.dissolved substances.

In a solution, the dissolving In a solution, the dissolving medium is the medium is the solventsolvent..

In a solution, the dissolved In a solution, the dissolved particles are the particles are the solutesolute..


The Solution ProcessThe Solution Process

The process by which the The process by which the positive and negative ions positive and negative ions of an ionic solid become of an ionic solid become surrounded by solvent surrounded by solvent molecules is called molecules is called solvation.solvation.

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The Solution ProcessThe Solution Process

Polar solvents such as Polar solvents such as water dissolve ionic water dissolve ionic compounds and polar compounds and polar compounds. compounds. Nonpolar solvents such Nonpolar solvents such as gasoline dissolve as gasoline dissolve nonpolar compounds.nonpolar compounds.

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Water and Its Properties >Electrolytes and Electrolytes and NonelectrolytesNonelectrolytes

An An electrolyteelectrolyte is a is a compound that conducts an compound that conducts an electric current when it is in electric current when it is in an aqueous solution or in the an aqueous solution or in the molten state. molten state. All ionic compounds are All ionic compounds are electrolytes because they electrolytes because they dissociate into ions.dissociate into ions.

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The bright glow shows The bright glow shows that sodium chloride is that sodium chloride is a a strong electrolytestrong electrolyte because nearly all the because nearly all the dissolved sodium dissolved sodium chloride exists as chloride exists as separate Naseparate Na++ and Cl and Cl–– ions.ions.

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A A weak weak electrolyteelectrolyte conducts conducts electricity poorly electricity poorly because only a because only a fraction of the fraction of the solute in the solute in the solution exists as solution exists as ions.ions.

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A compound that A compound that does not conduct does not conduct an electric an electric current in either current in either aqueous solution aqueous solution or the molten or the molten state is called a state is called a nonelectrolyte.nonelectrolyte.

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A compound that contains A compound that contains water of hydration is called a water of hydration is called a hydrate.hydrate. In writing the formula of a In writing the formula of a hydrate, use a dot to connect hydrate, use a dot to connect the formula of the compound the formula of the compound and the number of water and the number of water molecules per formula unit.molecules per formula unit.

HydratesHydrates15.2


HydratesHydrates To determine what percent of a To determine what percent of a

hydrate is water, first determine hydrate is water, first determine the mass of the number of moles of the mass of the number of moles of water in one mole of hydrate. Then water in one mole of hydrate. Then determine the total mass of the determine the total mass of the hydrate. The percent by mass of hydrate. The percent by mass of water can be calculated using this water can be calculated using this equation.equation.

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Sample Sample Problem 15.1Problem 15.1


Practice Problem For Practice Problem For Sample Problem 15.1Sample Problem 15.1


HydratesHydrates

Deliquescent CompoundsDeliquescent CompoundsDeliquescent compounds Deliquescent compounds remove sufficient water from remove sufficient water from the air to dissolve completely the air to dissolve completely and form solutions. These and form solutions. These compounds become wet compounds become wet when exposed to normally when exposed to normally moist air.moist air.

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1.1. Choose the correct words for the Choose the correct words for the spaces. In any solution, the material spaces. In any solution, the material that is dissolved is called the _______ that is dissolved is called the _______ and the material in which the substance and the material in which the substance is dissolved is called the _______ .is dissolved is called the _______ .

a) solid, liquida) solid, liquid

b) solvent, soluteb) solvent, solute

c) solute, solventc) solute, solvent

d) crystal, disperserd) crystal, disperser



2.2. In the solution process, the In the solution process, the

a) solvent molecules are a) solvent molecules are surrounded by positive and surrounded by positive and negative ions.negative ions.

b) solvent molecules become b) solvent molecules become dispersed in an ionic crystal.dispersed in an ionic crystal.

c) ions become emulsified in the c) ions become emulsified in the solvent.solvent.

d) positive and negative ions are d) positive and negative ions are surrounded by solvent molecules.surrounded by solvent molecules.



3.3. All ionic compounds are All ionic compounds are electrolytes because they electrolytes because they

a) conduct electricity in the solid a) conduct electricity in the solid state.state.

b) dissociate into ions in the b) dissociate into ions in the aqueous and/or the molten state.aqueous and/or the molten state.

c) remain as positive-negative pairs c) remain as positive-negative pairs even when dissolved.even when dissolved.

d) only conduct electricity in the d) only conduct electricity in the molten state.molten state.



4.4. The formula for iron(II) The formula for iron(II) sulfate heptahydrate issulfate heptahydrate is

a) FeSOa) FeSO44(H(H22O)O)77

b) FeSOb) FeSO44•(H•(H22O)O)77

c) Fe•2SOc) Fe•2SO44•7H•7H22OO

d) FeSOd) FeSO44•7H•7H22OO



15.3 15.3 Heterogeneous Heterogeneous

Aqueous SystemsAqueous Systems


SuspensionsSuspensions

A A suspensionsuspension is a mixture is a mixture from which particles settle out from which particles settle out upon standing. upon standing. A suspension differs from a A suspension differs from a solution because the solution because the particles of a suspension are particles of a suspension are much larger and do not stay much larger and do not stay suspended indefinitely.suspended indefinitely.

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ColloidsColloidsA A colloidcolloid is a is a heterogeneous mixture heterogeneous mixture containing particles that containing particles that range in size from 1 nm to range in size from 1 nm to 1000 nm. The particles in a 1000 nm. The particles in a colloid are spread colloid are spread throughout the dispersion throughout the dispersion medium.medium.

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ColloidsColloids The Tyndall EffectThe Tyndall Effect

The scattering of visible light The scattering of visible light by colloidal particles is called by colloidal particles is called the the Tyndall effectTyndall effect..

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ColloidsColloids Particles in colloids and Particles in colloids and

suspensions reflect or scatter suspensions reflect or scatter light in all directions. Solutions light in all directions. Solutions do not scatter light.do not scatter light.

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ColloidsColloids Brownian MotionBrownian Motion

The chaotic movement of colloidal The chaotic movement of colloidal particles, which was first observed by the particles, which was first observed by the Scottish botanist Robert Brown (1773–Scottish botanist Robert Brown (1773–1858), is called 1858), is called Brownian motion. Brownian motion.

Brownian motion is caused by Brownian motion is caused by collisions of the molecules of the collisions of the molecules of the dispersion medium with the small, dispersion medium with the small, dispersed colloidal particles.dispersed colloidal particles.

15.3

Water and Its Properties >ColloidsColloids

CoagulationCoagulation A colloidal system can be destroyed, or A colloidal system can be destroyed, or

coagulated, by the addition of ions having coagulated, by the addition of ions having a charge opposite to that of the colloidal a charge opposite to that of the colloidal particles. particles.

The added ions neutralize the charged The added ions neutralize the charged colloidal particles. The particles can clump colloidal particles. The particles can clump together to form heavier aggregates and together to form heavier aggregates and precipitate from the dispersion.precipitate from the dispersion.

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ColloidsColloids

Emulsions Emulsions An An emulsionemulsion is a colloidal is a colloidal dispersion of a liquid in a dispersion of a liquid in a liquid. An emulsifying agent liquid. An emulsifying agent is essential for the formation is essential for the formation of an emulsion and for of an emulsion and for maintaining the emulsion’s maintaining the emulsion’s stability.stability.

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1.1. One characteristic that is One characteristic that is unique to a suspension is that unique to a suspension is that the particles in it the particles in it

a) settle due to gravity.a) settle due to gravity.

b) are too small to be seen.b) are too small to be seen.

c) cannot be filtered.c) cannot be filtered.

d) produce the Tyndall effect.d) produce the Tyndall effect.



2.2. Homogenized milk contains Homogenized milk contains finely divided particles that do not finely divided particles that do not settle out rapidly and are not readily settle out rapidly and are not readily filtered. Thus, homogenized milk is a filtered. Thus, homogenized milk is a

a) colloid.a) colloid.

b) substance.b) substance.

c) suspension.c) suspension.

d) solution.d) solution.



3.3. The scattering of light The scattering of light known as the Tyndall effect can known as the Tyndall effect can be seen in be seen in

a) emulsions and solutions.a) emulsions and solutions.

b) colloids and suspensions.b) colloids and suspensions.

c) solutions and suspensions.c) solutions and suspensions.

d) colloids and solutions.d) colloids and solutions.


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Water and Its Properties > Chapter 15: Water and Aqueous Systems 15.1 Water and its Properties.

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