Properties of WaterProperties of Water

Water and Ocean StructureWater and Ocean Structure

The Water MoleculeThe Water Molecule

• HH22O = 1 oxygen atom O = 1 oxygen atom and 2 hydrogen atomsand 2 hydrogen atoms

• Polar molecule Polar molecule with with hydrogen atom positively hydrogen atom positively charged; oxygen atom charged; oxygen atom negatively charged.negatively charged.

• Atoms are linked by Atoms are linked by covalent bondscovalent bonds

• This polarity causes an attraction between This polarity causes an attraction between neighboring moleculesneighboring molecules

Dissolving Property of WaterDissolving Property of Water

• Positive hydrogen ion attracts negative chlorine ions; Positive hydrogen ion attracts negative chlorine ions; negative oxygen ion attracts positive sodium ionnegative oxygen ion attracts positive sodium ion

• Water’s dissolving ability related to molecular structureWater’s dissolving ability related to molecular structure

• Water separates compounds held together by Water separates compounds held together by opposite electrical charges, i.e. salt (Naopposite electrical charges, i.e. salt (Na++ + Cl + Cl--))

States of WaterStates of Water

• Water is only substance that naturally occurs in all 3 statesWater is only substance that naturally occurs in all 3 states

• HeatHeat is a measure of how many molecules are vibrating and is a measure of how many molecules are vibrating and how fasthow fast

• TemperatureTemperature is a measure of how rapidly the molecules are is a measure of how rapidly the molecules are vibratingvibrating • Thus, addition or loss of heat changes water’s physical propertyThus, addition or loss of heat changes water’s physical property

Latent HeatLatent Heat

• Latent Heat of FusionLatent Heat of Fusion • Latent Heat of VaporizationLatent Heat of Vaporization– Amount of heat needed to Amount of heat needed to

change from a solid to a change from a solid to a liquidliquid

– Amount of heat needed to Amount of heat needed to change from a liquid to a change from a liquid to a vaporvapor

Latent HeatLatent Heat

• Latent heat of vaporization (evaporation) is far greater Latent heat of vaporization (evaporation) is far greater than latent heat of fusion (melting).than latent heat of fusion (melting).

• All of the H bonds between HAll of the H bonds between H220 molecules must be broken 0 molecules must be broken to form vaporto form vapor

• Water - freezes 0Water - freezes 0°C; boils 100°C°C; boils 100°C

Heat Capacity of WaterHeat Capacity of Water

• Ability of a substance to Ability of a substance to change temperature with change temperature with a given amount of heata given amount of heat

• High heat capacity causes High heat capacity causes slow temperature changes slow temperature changes in world’s oceanin world’s ocean

• Water has a very high heat Water has a very high heat capacity compared to landcapacity compared to land

• Helps keep the Earth’s surface Helps keep the Earth’s surface temperature stabletemperature stable

Heat Capacity for Common Substances

Heat Capacity of WaterHeat Capacity of Water

Viscosity of WaterViscosity of Water

• The resistance of fluid The resistance of fluid to flowto flow

• Water has low viscosityWater has low viscosity

• Affected by temperatureAffected by temperature

• Surface water at equator Surface water at equator is warmer and less is warmer and less viscous than Arcticviscous than Arctic

Exxon Valdez 1989

Surface Tension of WaterSurface Tension of Water• Lateral and downward attraction Lateral and downward attraction

between individual moleculesbetween individual molecules

• Creates a strong boundary at Creates a strong boundary at surfacesurface

• ↑ ↑ salt = ↑ surface tensionsalt = ↑ surface tension

• ↓ ↓ HH22O temp = ↑ surface tensionO temp = ↑ surface tension

Water striderWater strider

Unique Property of WaterUnique Property of Water

• When liquid HWhen liquid H220 loses heat 0 loses heat and temperature lowers to and temperature lowers to freezing point, ice forms freezing point, ice forms

• Water expands as it Water expands as it freezesfreezes

• Ice less dense than Ice less dense than water water – ice floats– ice floats

Why does ice float on water?

– Angle between H and O Angle between H and O atoms in Hatoms in H220 molecule 0 molecule increases from 105° to increases from 105° to 109°109°

Density of WaterDensity of Water

• TemperatureTemperature

• SalinitySalinity

Density of water is affected by:Density of water is affected by:

– Below 4Below 4°C, density decreases°C, density decreases

– At 0At 0°C, ice forms, density °C, ice forms, density decreases rapidlydecreases rapidly

– As water first cools, density As water first cools, density increases and volume increases and volume decreasesdecreases

– Adding salts increasesAdding salts increases densitydensity

– Fresh HFresh H220 floats on salt H0 floats on salt H2200

Density of WaterDensity of Water

Compressibility of WaterCompressibility of Water

• Substance’s ability to Substance’s ability to undergo volume undergo volume changeschanges

• Water has slight Water has slight compressibilitycompressibility

• # of molecules/unit # of molecules/unit volume does not volume does not change muchchange much

Transmission of LightTransmission of Light

• No visible light below 1,000 mNo visible light below 1,000 m– Water absorbs red, orange, Water absorbs red, orange,

yellow and ultraviolet yellow and ultraviolet wavelengthswavelengths

– Only blue light remains Only blue light remains where it is reflected and where it is reflected and scattered scattered

• Intensity of light Intensity of light decreases with depthdecreases with depth

• Photic zone – maximum Photic zone – maximum light penetration light penetration

Why is the ocean blue?

• 65% of light absorbed in 165% of light absorbed in 1stst m m– Only 1% reaches 100 mOnly 1% reaches 100 m

Transmission of LightTransmission of Light• RefractionRefraction

– Light travels faster through Light travels faster through water than airwater than air

– As light passes from less As light passes from less dense air to more dense dense air to more dense water, it changes speed and water, it changes speed and bendsbends

Transmission of SoundTransmission of Sound

•Sound travels faster in waterSound travels faster in water

• Sound velocity in water = Sound velocity in water = 1,500 m/sec (5x greater 1,500 m/sec (5x greater than in air)than in air)

• Sound speed increases Sound speed increases with pressure, with pressure, temperature and salinitytemperature and salinity

• Use sound with sonarUse sound with sonar

Sound and Locating ObjectsSound and Locating Objects

• When sound speed decreases with depth, waves are bent When sound speed decreases with depth, waves are bent downwarddownward• When sound speed increases with depth, waves are bent When sound speed increases with depth, waves are bent upwardupward• An area exists where no sound waves travel – An area exists where no sound waves travel – shadow zoneshadow zone