Lesson 1
• Describe the unique properties of water and how these
properties support life on Earth (e.g. freezing point, high
specific heat, cohesion)
• Chemicals are the things that make up:
• Our body
• The bodies of organisms
• The physical environment
• Life’s chemistry is tied to water!
• Life first evolved in water
• All living things require water
• The chemical reactions of your body occur in cells
consisting of 70–95% water.
• Water is a very small polar
molecule
–Each molecule has charges
that can attract opposite
charges including other water
molecules
–The attractions between these
slight charges are called
Hydrogen bonds (dotted lines)
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Eurico Zimbres via Wikimedia Commons
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• Cohesion holds water together
• Adhesion holds water
molecules to other polar
substances
• Surface tension is caused by
cohesion of water to itself and
lack of adhesion to air
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Via Wikimedia Commons
• Water has an extremely high specific heat (amount of
energy needed to raise the temperature)
–Energy is stored in hydrogen bonds and molecular motion
• Water moderates temperature
• Heat vs. Temperature
–Heat is the total kinetic energy stored in an object (related to
mass)
–Temperature is the average kinetic energy (mass doesn’t
matter)
• Ice is less dense than water
• Hydrogen bonds hold molecules apart in crystal structure (more
space in between molecules)
• Insulates bodies of water from freezing solid
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Via Wikimedia Commons
• Water dissolves a huge range of
compounds
• Solution – evenly distributed mixture
of 2 or more substances
• Solvent – Dissolving substance (usually
water)
• Solute – dissolved substance
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Via Wikimedia Commons
• Hydrophobic substances do not form
Hydrogen bonds with water (oils,
membranes, some proteins, etc.)
• Hydrophilic substances form Hydrogen
bonds with water (ions, sugars, cellulose,
some proteins, etc.)
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Wikimedia Commons
Public Domain via Wikimedia Commons
• Water spontaneously disassociates
into a hydronium ion and a
hydroxide ion
• Acids increase H+ concentration
and lower pH
• Bases decrease H+ concentration
and increase pH
Creative Commons,
Courtesy of
Edward Stevens
via Wikimedia Commons