water’s life support properties text pg. 25 - 26
TRANSCRIPT
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