2.2 water
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Transcript of 2.2 water
Water (H2O)
• There is a ratio of 2:1 for Hydrogen: Oxygen
• Water is a compound formed from two elements:
oxygen and hydrogen
Forming a water molecule
covalent bonding
• Hydrogen has 1 valence electron
• An oxygen shares an electron with two hydrogen
atoms, forming two covalent bonds
• Oxygen has 6 valence electrons
Polarity of water
• Water is a unique substance earth, and
therefore essential to life, because of
its polar nature
Partial Charge• Oxygen exerts a great pull over the shared
electrons. They move a little closer to the oxygen
• That means that the oxygen part of the molecule is
slightly negative
• The hydrogen end of the molecule is slightly
positive
Polarity relates to
solubility in waterHydrophillic
• A substance that is attracted to water and forms
intermolecular bonds with water molecules
• Ionic compounds and substances with polar molecules
Hydrophobic
• Means that waters molecules are more strongly attracted to
each other than to the substances
• Hydrophobic substances are insoluble in water
The Nature of Science
• Theories are used to explain natural
phenomena
• Hydrogen bonding explains the unique
behaviour of water that allows life on
earth
Water is Cohesive
Explanation
• Water molecules cohere because hydrogen
bonds form between them
Example of benefits to organisms
• Transpiration stream
Water is Adhesive
Explanation
• The polarity of water molecules makes them
adhere to surfaces that are polar (and therefore
hydrophillic)
Example of benefits to organisms
• Transpiration stream & gas exchange in plants
Water has Thermal
PropertiesExplanation
• High melting point & boiling point
• High latent heat of vaporization
• High specific heat capacity
Example of benefits to organisms
• Liquid (aquatic) habitats that are stable
• Effective coolant in leaves or sweat
Water is a Solvent
Explanation
• Many molecules dissolve in water due to its
polarity including ions or polar molecules
Example of benefits to organisms
• Medium for metabolic reactions