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Hydrogen Bonds Polar water molecules act like magnets and attract each other Hydrogen Bonds –The attraction of the Hydrogen end (+) of one molecule for the Oxygen end (-) of another water molecule.
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The Chemistry of Life
Properties of Water
The Water MoleculeThe Water Molecule• Polarity
– Polar molecules have a region with a slight positive charge and a slight negative charge.
– A water molecule is polar because there is an uneven distribution of electrons between the oxygen and hydrogen atoms.
• Oxygen has 8 protons and a larger pull on the electrons than Hydrogen with just 1 proton.
Hydrogen BondsHydrogen Bonds• Polar water molecules act like
magnets and attract each other • Hydrogen Bonds
– The attraction of the Hydrogen end (+) of one molecule for the Oxygen end (-) of another water molecule.
Hydrogen BondsHydrogen Bonds
CohesionCohesion• The attraction
between molecules of the same substance (e.g. water).
• Allows some insects and spiders to walk on water.
AdhesionAdhesion• Attraction between molecules of
different substances• Responsible for Capillary forces
in plants
Solutions & Solutions & SuspensionsSuspensions
• Water is usually part of a mixture.
• There are two types of mixtures:–Solutions–Suspensions
SolutionSolution• Made of a solute and solvent.• Ionic compounds disperse as ions in
water (NaCl becomes Na+ Cl-)• Evenly distributed• SOLUTE
– Substance that is being dissolved• SOLVENT
– Substance into which the solute dissolves
SolutionSolution
SuspensionsSuspensions• Substances that
don’t dissolve but separate into tiny pieces.
• Water keeps the pieces suspended so they don’t settle out.
Acids, Bases & pHAcids, Bases & pH• 1 water molecule in 550 million
naturally dissociates into a Hydrogen Ion and a Hydroxide Ion
Hydrondium Ion Hydroxide Ion Acid Base
H2O H+ + OH-
The pH ScaleThe pH Scale• Indicates the concentration of H+ ions• Ranges from 0 – 14• pH of 7 is neutral• pH 0 – 6.99 is acid … H+ • pH 7.01 – 14 is basic… OH- • Each pH unit represents a factor of
10 change in concentration
AcidsAcids• Strong Acid
= pH 1-3 H+ ions
BasesBases• Strong Base
= pH 11 – 14 OH-
ions
BuffersBuffers• Weak acids or bases that react
with strong acids or bases to prevent sharp, sudden changes in pH.
Weak Acid Weak Base