Properties of Water Water and Ocean Structure

The Water Molecule H 2 O = 1 oxygen atom and 2 hydrogen atomsH 2 O = 1 oxygen atom and 2 hydrogen atoms Polar molecule with hydrogen atom positively charged; oxygen atom negatively charged.Polar molecule with hydrogen atom positively charged; oxygen atom negatively charged. Atoms are linked by covalent bondsAtoms are linked by covalent bonds This polarity causes an attraction between neighboring moleculesThis polarity causes an attraction between neighboring molecules

Dissolving Property of Water Positive hydrogen ion attracts negative chlorine ions; negative oxygen ion attracts positive sodium ion Positive hydrogen ion attracts negative chlorine ions; negative 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 opposite electrical charges, i.e. salt (Na + + Cl - )Water separates compounds held together by opposite electrical charges, i.e. salt (Na + + Cl - )

States of Water Water is only substance that naturally occurs in all 3 statesWater is only substance that naturally occurs in all 3 states Heat is a measure of how many molecules are vibrating and how fastHeat is a measure of how many molecules are vibrating and how fast Temperature is a measure of how rapidly the molecules are vibratingTemperature is a measure of how rapidly the molecules are vibrating Thus, addition or loss of heat changes water’s physical propertyThus, addition or loss of heat changes water’s physical property

Latent Heat Latent Heat of FusionLatent Heat of Fusion Latent Heat of VaporizationLatent Heat of Vaporization – Amount of heat needed to change from a solid to a liquid – Amount of heat needed to change from a liquid to a vapor

Latent Heat Latent heat of vaporization (evaporation) is far greater than latent heat of fusion (melting). Latent heat of vaporization (evaporation) is far greater than latent heat of fusion (melting). All of the H bonds between H 2 0 molecules must be broken to form vaporAll of the H bonds between H 2 0 molecules must be broken to form vapor Water - freezes 0°C; boils 100°CWater - freezes 0°C; boils 100°C

Heat Capacity of Water Ability of a substance to change temperature with a given amount of heatAbility of a substance to change temperature with a given amount of heat High heat capacity causes slow temperature changes in world’s oceanHigh heat capacity causes slow temperature changes in world’s ocean Water has a very high heat capacity compared to landWater has a very high heat capacity compared to land Helps keep the Earth’s surface temperature stableHelps keep the Earth’s surface temperature stable Heat Capacity for Common Substances

Heat Capacity of Water

Viscosity of Water The resistance of fluid to flowThe resistance of fluid to flow Water has low viscosityWater has low viscosity Affected by temperatureAffected by temperature Surface water at equator is warmer and less viscous than ArcticSurface water at equator is warmer and less viscous than Arctic Exxon Valdez 1989

Surface Tension of Water Lateral and downward attraction between individual molecules Lateral and downward attraction between individual molecules Creates a strong boundary at surfaceCreates a strong boundary at surface ↑ salt = ↑ surface tension ↑ salt = ↑ surface tension ↓ H 2 O temp = ↑ surface tension ↓ H 2 O temp = ↑ surface tension Water strider

Unique Property of Water When liquid H 2 0 loses heat and temperature lowers to freezing point, ice formsWhen liquid H 2 0 loses heat and temperature lowers to freezing point, ice forms Water expands as it freezesWater expands as it freezes Ice less dense than water – ice floatsIce less dense than water – ice floats Why does ice float on water? – Angle between H and O atoms in H 2 0 molecule increases from 105° to 109°

Density of Water TemperatureTemperature SalinitySalinity Density of water is affected by: – Below 4°C, density decreases – At 0°C, ice forms, density decreases rapidly – As water first cools, density increases and volume decreases – Adding salts increasesdensity – Adding salts increases density – Fresh H 2 0 floats on salt H 2 0

Density of Water

Compressibility of Water Substance’s ability to undergo volume changesSubstance’s ability to undergo volume changes Water has slight compressibilityWater has slight compressibility # of molecules/unit volume does not change much# of molecules/unit volume does not change much

Transmission of Light No visible light below 1,000 m No visible light below 1,000 m – Water absorbs red, orange, yellow and ultraviolet wavelengths – Only blue light remains where it is reflected and scattered Intensity of light decreases with depthIntensity of light decreases with depth Photic zone – maximum light penetrationPhotic zone – maximum light penetration Why is the ocean blue? 65% of light absorbed in 1 st m65% of light absorbed in 1 st m – Only 1% reaches 100 m

Transmission of Light Refraction Refraction – Light travels faster through water than air – As light passes from less dense air to more dense water, it changes speed and bends

Transmission of Sound Sound travels faster in waterSound travels faster in water Sound velocity in water = 1,500 m/sec (5x greater than in air)Sound velocity in water = 1,500 m/sec (5x greater than in air) Sound speed increases with pressure, temperature and salinitySound speed increases with pressure, temperature and salinity Use sound with sonarUse sound with sonar

Sound and Locating Objects When sound speed decreases with depth, waves are bent downwardWhen sound speed decreases with depth, waves are bent downward When sound speed increases with depth, waves are bent upwardWhen sound speed increases with depth, waves are bent upward An area exists where no sound waves travel – shadow zoneAn area exists where no sound waves travel – shadow zone