Thirsty Seawater:
• Drinking seawater can cause dehydration.
• Seawater
– is a homogeneous mixture of salts with water.
– contains higher concentrations of salts than the salt content of
your cells.
• As seawater passes through your body, it pulls water out of your cells,
due mainly to nature’s tendency toward spontaneous mixing.
• This reduces your cells’ water level and usually results in diarrhea as
this extra liquid flows out with the seawater.
• Drinking seawater will dehydrate you and give you diarrhea.
• The cell wall acts as a barrier to the solute moving, so the only way for
the seawater and the cell solution to have uniform mixing is for water
to flow out of the cells of your intestine and into your digestive tract
Solutions:
• The majority component of a solution is called
the solvent.
• The minority component is called the solute.
• Solutions form in part because of intermolecular forces.
– The particles of the solute interact with the particles of the
solvent through intermolecular forces.
1
,Homogeneous Mixtures
• A mixture of two or more substances
• Composition may vary from one sample to another
• Appears to be one substance, though really contains multiple materials
• Most homogeneous materials we encounter are actually solutions.
– For example, air and seawater
• Nature has a tendency toward spontaneous mixing.
– Generally, uniform mixing is more energetically favorable.
Spontaneous Mixing:
When solutions with different solute concentrations come in contact, they
spontaneously mix to result in a uniform distribution of solute throughout the
solution.
Common Types of Solutions:
A solution may be composed of a solid and a liquid or any other combination.
In aqueous solutions, water is the solvent.
2
, Solubility:
• When one substance (solute) dissolves in another (solvent) it is said to
be soluble.
– Salt is soluble in water.
– Bromine is soluble in methylene chloride.
• When one substance does not dissolve in another it is said to be
insoluble.
– Oil is insoluble in water.
• The solubility of one substance in another
depends on
1. nature’s tendency toward mixing, and
2. the types of intermolecular attractive forces
Nature’s Tendency Toward Mixing: Entropy:
• Many physical systems tend toward lower potential energy.
• But formation of a solution does
not necessarily lower the potential energy of the system.
• When two ideal gases are put
into the same container, they spontaneously mix, even though
the difference in attractive forces is negligible.
• The gases mix because the energy
of the system is lowered through the release of entropy.
Mixing and the Solution Process Entropy:
• Entropy is the measure of energy dispersal in a system.
• Energy has a spontaneous drive to spread out over as large a volume
as it is allowed.
• By each gas expanding to fill the container, the gases’ energy is
dispersed over a larger volume.
Solutions: Effect of Intermolecular Forces
• Energy changes in the formation of most solutions also involve
differences in attractive forces between the particles.
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