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Solutions
Earth Science II
(Session 16)
Ciencias de la Tierra II
Solutions and its
components
• A solution is a homogenous mixture
composed by a solute dissolved in a
solvent.
• The solute is the least present component.
• The solvent is present in a larger size.
• For example, a spoon full of sugar dissolved
in a glass of water forms a watery solution
where the sugar is the solute and the water
is the solvent or dissolvent.
• The name watery solution is given to every
solution where water is the solvent.
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.
• The solute and the solvent of a solution
can exist as molecules or ions.
• For example, when sugar is dissolved in
water, the sugar enters the solution in
molecule form.
• When the sodium chloride is dissolved
in water it is separated in chloride ions
and sodium ions.
• In both cases the molecules and the
solute ions are surrounded by the water
molecules in the solution.
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Solubility of Covalent
Compounds
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Solvatation process
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Burns, R. (1996)
Electrolytes
• A substance that breaks into ions when
dissolved forms a solution known as
electrolyte.
• When the substance is not ionized it is
called non electrolyte.
• There are two types of electrolytes:
– Strong: when they are completely ionized.
– Weak: when they are partially ionized.
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Factors that affect the
solubility
• Properties of the solvent and solute: The
ionic compounds are soluble in polar solvents,
the covalent compounds are soluble in non
polar solvents.
– “The similar dissolves the similar”
• Temperature: Gas solutions in a liquid, their
solubility decreases with the increase in
temperature. Solid solutions in a liquid
generally increase their solubility when the
temperature increases.
• Pressure: Solutions that contain solids and
liquids are not affected by changes in
pressure. The solubility of a gas in a liquid is
directly proportionate to the partial pressure of
a gas over a liquid.
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Factors that affect the
speed of dissolution
• Size of a particle: At less size of a particle
in a solute greater the dissolution speed.
• Mixing speed: The speed of dissolution of
a solute increases when mixed.
• Temperature: At higher temperature
greater the dissolution speed.
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Solution types
• Non saturated solutions: It is a solution where
there is less solute then what can be dissolved
at a given temperature.
• Saturated solution: It is a solution that has
enough solute that can be dissolved at a given
temperature.
• Oversaturated solution: It is an unstable
solution that has more solute then what normally
exists at a given temperature. If a crystallization
process is created, all the solute excess is
precipitated, living a saturated solution.
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Solution types
Brown, T. et al. (1991)
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Bibliography
• Brown, T. et al. (1991) Chemistry: The
Central Science. 5th ed. United States
of America: Prentice Hall.
• Burns, R. (1996) Fundaments of
Chemistry. 2nd. ed. United States of
America: Prentice Hall.
• DiSpezio, M. et al. (1999) Science
Insights: Exploring Earth and Space.
1st ed. United States of America:
Prentice Hall.
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