properties of water. a compound is a pure substance made up of atoms of two or more elements the...
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Properties of Water
A compound is a pure substance made up of atoms of two or more elementsThe proportion of atoms
are always fixedChemical formula shows
the kind and proportion of atoms of each element that occurs in a particular compound
Molecules are the simplest part of a substance that retains all of the properties of the substance and exists in a free state
Some molecules are large and complex
Chemical FormulasChemical FormulasSubscript after a symbol tell the number
of atoms of each elementH20 has 2 atoms of hydrogen & 1 atom
of oxygenCoefficients before a formula tell the
number of molecules3O2 represents 3 molecules of oxygen or
(3x2) or 6 atoms of oxygen
The extraordinary properties of Water
•At sea level, pure water boils at 100 °C and freezes at 0 °C.
•The boiling temperature of water decreases at higher elevations (lower atmospheric pressure). •For this reason, an egg will take longer to boil at higher altitudes.
The Water Molecule
Neutral ChargeAll Molecules Are Neutral
The Water MoleculeThe Water MoleculePolarityPolarity
A water molecule is polar because there is an uneven distribution of electrons between the oxygen and hydrogen atoms.
(+)
(—)
Hydrogen BondsHydrogen BondsPolar water molecules Polar water molecules act like act like
magnetsmagnets and attract each other and attract each other Hydrogen BondsHydrogen Bonds
The attraction of the Hydrogen The attraction of the Hydrogen end (+) of one molecule for the end (+) of one molecule for the Oxygen end Oxygen end (-)(-) of another water of another water molecule.molecule.
They are the They are the strongest bondsstrongest bonds that can form that can form betweenbetween moleculesmolecules
Hydrogen BondsHydrogen Bonds
CohesionCohesionThe attraction between molecules of the same substance (e.g. water).
Allows some insects and spiders to walk on water.
AdhesionAdhesionAttraction between Attraction between molecules of different molecules of different substancessubstances
Responsible for Capillary Responsible for Capillary forces in plantsforces in plants
High Specific Heat
•Water resists temperature change, both for heating and cooling.
•Water can absorb or release large amounts of heat energy with little change in actual temperature.
Homeostasis
Steady stateConstant physiological condition of cells,
organisms global ecosystemsa. Makes a good insulatorb. Resists temperature changec. Universal solventd. Coolante. Ice protects against temperature
extremes
Solutions & Solutions & SuspensionsSuspensions
Water is usually part of a Water is usually part of a mixturemixture..
There are two types of There are two types of mixtures:mixtures:SolutionsSolutionsSuspensionsSuspensions
SolutionSolutionIonic compounds disperse as Ionic compounds disperse as
ions in waterions in waterEvenly distributedEvenly distributedSOLUTESOLUTE
Substance that is being Substance that is being dissolveddissolved
SOLVENTSOLVENTSubstance into which the Substance into which the solute dissolvessolute dissolves
SolutionSolution
SuspensionsSuspensionsSubstances that Substances that
don’t dissolve don’t dissolve but separate but separate into tiny pieces.into tiny pieces.
Water keeps Water keeps the pieces the pieces suspended so suspended so they don’t settle they don’t settle out.out.
Acids, Bases & pHAcids, Bases & pH1 water molecule in 550 million 1 water molecule in 550 million naturally dissociates into a naturally dissociates into a Hydrogen IonHydrogen Ion and a and a Hydroxide IonHydroxide Ion
Hydrogen Ion Hydroxide IonHydrogen Ion Hydroxide Ion Acid Acid BaseBase
H2O H+ + OH-
The pH ScaleThe pH ScaleIndicates the concentration of H+ ions
Ranges from 0 – 14pH of 7 is neutralpH 0 – 6.99 is acid … H+ pH 7.01 – 14 is basic… OH- Each pH unit represents a factor of 10 change in concentration
AcidsAcidsStrong Acid = pH 1-3
H+ ions
BasesBasesStrong Base = pH 11 – 14 OH-ions
BuffersBuffersWeak acids or bases that Weak acids or bases that react with strong acids or react with strong acids or bases to prevent sharp, bases to prevent sharp, sudden changes in pH.sudden changes in pH.
Weak AcidWeak Acid Weak BaseWeak Base
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