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Chapter 2Chapter 2

An Introduction An Introduction to Chemistryto Chemistry

Lecture 7: Properties of WaterLecture 7: Properties of Water

•• Organic moleculesOrganic molecules

•• Primary structure from carbonPrimary structure from carbon--carbon bondscarbon bonds

•• Most biological moleculesMost biological molecules

•• Examples: carbohydrates, lipids, proteinsExamples: carbohydrates, lipids, proteins

Types of CompoundsTypes of Compounds

•• Inorganic moleculesInorganic molecules

•• Primary structure from anything except Primary structure from anything except

carboncarbon--carbon bondscarbon bonds

•• Examples: NHExamples: NH33, O, O22, , NaClNaCl, CO, CO22

•• Most important for life is waterMost important for life is water

Types of CompoundsTypes of Compounds

•• We are mostly water!We are mostly water!

•• All chemical processes for life occur in waterAll chemical processes for life occur in water

•• Metabolism stops if cell’s water content drops Metabolism stops if cell’s water content drops

below 50%below 50%

Properties of WaterProperties of Water

•• Keys to water’s unique propertiesKeys to water’s unique properties

•• PolarityPolarity

•• Hydrogen bondsHydrogen bonds

Properties of WaterProperties of Water

•• Cohesion: Cohesion: the ability of molecules of a single the ability of molecules of a single

compound to stick togethercompound to stick together

•• Water likes to stick to itselfWater likes to stick to itself

•• Due to hydrogen bondsDue to hydrogen bonds

Properties of WaterProperties of Water

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•• Adhesion:Adhesion: the ability of molecules of one the ability of molecules of one

compound to stick to molecules of another compound to stick to molecules of another

compoundcompound

•• Water likes to stick to other moleculesWater likes to stick to other molecules

•• Due to polarity (not necessarily hydrogen bonds)Due to polarity (not necessarily hydrogen bonds)

Properties of WaterProperties of Water

Water sticking to itselfWater sticking to itself

Water sticking toWater sticking to

Something elseSomething else

•• The balance between these forces leads to all The balance between these forces leads to all

kinds of phenomenakinds of phenomena

Properties of WaterProperties of Water

•• The balance between these forces leads to all The balance between these forces leads to all

kinds of phenomenakinds of phenomena

Properties of WaterProperties of Water

•• The balance between these forces leads to all The balance between these forces leads to all

kinds of phenomenakinds of phenomena

Properties of WaterProperties of Water

•• Surface tensionSurface tension

•• Hydrogen bonds at the surface of water are Hydrogen bonds at the surface of water are

especially strongespecially strong

•• Reduces evaporationReduces evaporation

•• Acts as barrier (example: eyes)Acts as barrier (example: eyes)

Properties of WaterProperties of Water

•• Surface tensionSurface tension

Properties of WaterProperties of Water

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•• Surfactants are substances that disrupt surface Surfactants are substances that disrupt surface

tensiontension

•• Examples: soap, egg yolk, EDTA, fabric Examples: soap, egg yolk, EDTA, fabric

softeners, laxatives, insecticidessofteners, laxatives, insecticides

Properties of WaterProperties of Water

•• Lung surfactantLung surfactant

Properties of WaterProperties of Water

•• Heat capacityHeat capacity Specific heatSpecific heat

•• Measure of how much thermal energy a Measure of how much thermal energy a

substance can absorb without changing substance can absorb without changing

temperaturetemperature

•• How much heat it can storeHow much heat it can store

Properties of WaterProperties of Water

•• Specific heatSpecific heat

•• Water has a VERY high specific heat Water has a VERY high specific heat –– the the

second highest found in naturesecond highest found in nature

•• Remarkable because of small massRemarkable because of small mass

•• Due to hydrogen bondsDue to hydrogen bonds

Properties of WaterProperties of Water

•• Specific heatSpecific heat

•• Makes water a very efficient insulatorMakes water a very efficient insulator

Properties of WaterProperties of Water

•• Due to its high specific heat, water is excellent Due to its high specific heat, water is excellent

for evaporative coolingfor evaporative cooling

•• ALL hydrogen bonds must be broken for water ALL hydrogen bonds must be broken for water

to escape and become a gasto escape and become a gas

•• Takes a tremendous amount of energyTakes a tremendous amount of energy

Properties of WaterProperties of Water

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•• Energy is supplied by the molecules underneathEnergy is supplied by the molecules underneath

•• Leaves the substance coolerLeaves the substance cooler

Properties of WaterProperties of Water

•• LubricationLubrication

•• Water is virtually incompressibleWater is virtually incompressible

•• Molecules pass over each other easilyMolecules pass over each other easily

•• Reduces frictionReduces friction

Properties of WaterProperties of Water

•• Universal solventUniversal solvent

•• Can dissolve ionic, polar, and some nonCan dissolve ionic, polar, and some non--polar polar

substancessubstances

Properties of WaterProperties of Water

•• Complete the concept map on page 2Complete the concept map on page 2--47 of your 47 of your

study guidestudy guide

•• Complete the fillComplete the fill--inin--thethe--blank worksheet on blank worksheet on

pages 2pages 2--51 and 251 and 2--52 of your study guide 52 of your study guide

(skip the matching at the bottom of page 2(skip the matching at the bottom of page 2--52)52)

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