Water’s Life Water’s Life support support

PropertiesPropertiesText pg. 25 - 26Text pg. 25 - 26

Polar Covalent BondsPolar Covalent Bonds Water has atoms with different Water has atoms with different

electronegativitieselectronegativities– Oxygen attracts the shared electrons more Oxygen attracts the shared electrons more

strongly than hydrogenstrongly than hydrogen– So, the shared electrons spend more time near So, the shared electrons spend more time near

oxygen oxygen – The result is a The result is a polar covalent bondpolar covalent bond

In HIn H22O the oxygen atom has a slight negative O the oxygen atom has a slight negative charge and the hydrogens have a slight positive charge and the hydrogens have a slight positive chargecharge

– Molecules with this Molecules with this unequal distribution of unequal distribution of chargescharges are called are called polar moleculespolar molecules

Hydrogen Bonds Hydrogen Bonds

Hydrogen, within a polar covalent Hydrogen, within a polar covalent bond, is attracted to electronegative bond, is attracted to electronegative atoms in other molecules.atoms in other molecules.– called a called a hydrogen bondhydrogen bond

– Is responsible for holding

together 2 separate water

molecules

CohesionCohesion

Hydrogen bonding causes molecules Hydrogen bonding causes molecules to stick together, a property called to stick together, a property called cohesioncohesion

Cohesion is related to Cohesion is related to surfacesurface tensiontension - a measure of how difficult - a measure of how difficult it is to break the surface of a liquidit is to break the surface of a liquid– Hydrogen bonds are responsibleHydrogen bonds are responsible

for surface tensionfor surface tension

AdhesionAdhesion

AdhesionAdhesion is the clinging of one is the clinging of one substance to another unlike itself. substance to another unlike itself.

Caused by adhesion the water runs along the glass and does not fall straight.

Capillary Action is a result Capillary Action is a result of a combination of of a combination of

cohesion and adhesioncohesion and adhesion Capillary ActionCapillary Action is the is the

ability of water to flow up ability of water to flow up a thin tube against a thin tube against gravitygravity

It is due to a combination It is due to a combination of cohesion and adhesionof cohesion and adhesion

Examples:Examples: Water soaking up a paper Water soaking up a paper

toweltowel Water turning up the side Water turning up the side

of a test tubeof a test tube

Capillary action is the Capillary action is the mechanism behind mechanism behind

transpirationtranspiration

Cohesion

Adhesion

Water-conductingcellsDirection

of watermovement

Transpiration is the process by which water is pulled from the roots of a plant all the way up and out of the leaves.

Water - The Universal Water - The Universal SolventSolvent

Solvent – Solvent – liquid that can dissolve other substancesliquid that can dissolve other substances Solute – Solute – substance that dissolves in a solventsubstance that dissolves in a solvent

HYDROPHILIC (WATER LOVING) SUBSTANCESHYDROPHILIC (WATER LOVING) SUBSTANCES Ionic substances are soluble (they dissolve) in water Ionic substances are soluble (they dissolve) in water

because the poles of the polar water molecules interact because the poles of the polar water molecules interact with the ionic substances and separate them into ions.with the ionic substances and separate them into ions.

Polar covalent substances are also soluble of the Polar covalent substances are also soluble of the interaction with their poles with waterinteraction with their poles with water

HYDROPHOBIC (WATER HATING) SUBSTANCESHYDROPHOBIC (WATER HATING) SUBSTANCES Nonpolar covalent substances do not dissolve in water Nonpolar covalent substances do not dissolve in water

because they lack charged polesbecause they lack charged poles

EX. WATER AND OIL BOTTLESEX. WATER AND OIL BOTTLES

Water’s hydrogen bonds Water’s hydrogen bonds moderate temperaturemoderate temperature

Has a greater ability to resist temperature Has a greater ability to resist temperature change because of hydrogen bonds.change because of hydrogen bonds.

– HeatHeat is the energy associated with movement is the energy associated with movement of atoms and molecules in matterof atoms and molecules in matter

– TemperatureTemperature measures the intensity of heat measures the intensity of heat

***** When it is cool outside, water will be warmer than the air. When it is warm outside, the water will be colder than the air.

Specific Heat CapacitySpecific Heat Capacity

Specific heat capacitySpecific heat capacity – the degree to – the degree to which a substance changes temperature which a substance changes temperature in response to a gain or loss of heatin response to a gain or loss of heat

Water has a high specific heat, with so Water has a high specific heat, with so many hydrogen bonds between water many hydrogen bonds between water molecules, it can absorb a great deal of molecules, it can absorb a great deal of heat, with only a slight temperature heat, with only a slight temperature change. change. Compare the water in a pool on a hot day, Compare the water in a pool on a hot day,

and a metal chair next to the pooland a metal chair next to the pool

Heat of fusion and heat Heat of fusion and heat of vaporizationof vaporization

When water changes physical states, When water changes physical states, from solid to liquid or liquid to gas, from solid to liquid or liquid to gas, energy is absorbed but the water energy is absorbed but the water temperature remains constant. temperature remains constant. The absorbed energy is used only to change The absorbed energy is used only to change

the physical state of the water by breaking the physical state of the water by breaking the hydrogen bonds that tether the water the hydrogen bonds that tether the water molecules together. molecules together.

In the reverse reactions, from gas to liquid or In the reverse reactions, from gas to liquid or liquid to solid, the energy released liquid to solid, the energy released reestablishes the hydrogen bonds. reestablishes the hydrogen bonds.

Heat of fusion and heat Heat of fusion and heat of vaporizationof vaporization

IceIce Most types of matter are more dense as a solid Most types of matter are more dense as a solid Water is different in that when water freezes, Water is different in that when water freezes,

each molecule forms a stable hydrogen bond each molecule forms a stable hydrogen bond with four neighborswith four neighbors– A three-dimensional crystal resultsA three-dimensional crystal results– There is There is space between the water moleculesspace between the water molecules

(This is not the case with most solids. This is (This is not the case with most solids. This is the reason why you can bite into and break the reason why you can bite into and break ice.) ice.)

Ice is less dense than water, so it floatsIce is less dense than water, so it floats

IceWater moleculesAre spaced out

Liquid waterWater molecules

are closer together