# BSC-2010 Lecture Notes - Lecture 1: Heat Capacity, Kinetic Energy, Chemical Equilibrium

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20 Oct 2016
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9/7/16
Chapter 3 Water
Chemical equilibrium is reached when the forward and reverse reactions
occur at the sane rate
Water is the biological medium on Earth
Water is the only common substance to exist in all three physical states of
matter.
In water, the electrons of the polar convalent bonds spend more time near
the oxygen then hydrogen.
Four of water’s properties that facilitate an environment for life are
o Cohesive behavior
Hydrogen bonds hold water molecules together, helps the
transport of water against gravity in plants
o Ability to moderate temp
Water absorbs heat from warmer air and releases stored heat
to cooler air
o Expansion upon freezing
o Versatility as a solvent
A solution is a liquid that is a completely homogeneous
mixture of substances
A solvent is the dissolving agent of a solution
The solute is the substance that is dissolved
An aqueous solution is one in which water is the solvent
Surface tension is a measure of how hard it is to break the surface of a liquid
Kinetic energy is the energy of motion
A calorie (cal) is the amount of heat required to raise the temperature of 1 g
of water by 1°C
Kcal = 1000 cal
The joule (J) is another unit of energy where
1 J = 0.239 cal, or 1 cal = 4.184 J
The specific heat of water is 1 cal/g/°C
Water resists changing its temperature because of its high specific heat
Heat absorbed when hydrogen bonds break
Heat released when hydrogen bonds form
Evaporation = liquid to gas
Ice floats in liquid water because hydrogen bonds in ice are more ordered
making it less dense
Water’s greatest density at 4 C
A hydrophilic substance is one that has an
affinity for water
A hydrophobic substance is one that does not have an affinity for water
Adding certain solutes, called acids and bases, modifies the concentrations of
H+ and OH
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