SOLUTIONS and OSMOSIS INFO:
DO NOT WRITE ON THIS PAGE.
Most chemical reactions occur in
solution. A solution is a special
kind of mixture, in which one or
more substances are dissolved in
another.
Some common examples include:
*Salt dissolved in cooking water
*Sugar dissolved in syrups or drinks.
*Electrolytes dissolved in water within
your body.
Solution
Solute
Solvent
A homogenous
mixture in which
one substance is
dissolved in
another
The substance
that is dissolved
in a mixture
The substance
that dissolves
another to form a
solution
Not all solutions involve a solid dissolved in a liquid, but since that is the kind of solution most
often used in cooking, that is what we will focus on for class. (The air in your kitchen can also be a
solution that affects food.)
Here is some important information to know about solutions:
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A solution is homogenous.
Once a solution is completely mixed, every part of it is the same as
any other part. Gravity and filters do not separate solutions. (Sugar water is a homogenous solution. On the
other hand, cinnamon sugar is a heterogenous mixture—parts are different from each other---some parts are
sugar, and some are cinnamon.)
One solution may vary from others in concentration. Although all parts of a
solution are equally concentrated, one solution may have a higher concentration of solute than another.
(You could stir lots of sugar into coffee one day, less in on another day. You could put lots of salt into
cooking water for one recipe, but less in for another recipe.) The concentration of solute will affect the
properties of the solution.
Dilute solutions have a low amount of solute in the solvent.
Concentrated solutions have a high amount of solute in the solvent.
A solution has a saturation point. When you add a solute to a solvent, it dissolves. However,
you reach a point where the solvent cannot hold any more solute. This is called the saturation point. (One
way of increasing the saturation point is by increasing the temperature of the solution. so, if you want more
of the solute to dissolve, try heating your solution.)
A solution has different freezing and boiling points than its solvent. Solid
solutes increase the boiling point and decrease the freezing point of their liquid solvents. The greater the
number of solute molecules, the greater the change in boiling and freezing point. This is important in
cooking.
A solution shows an increase in osmotic pressure as the amount of solute is
increased. A semipermeable membrane allows molecules of one kind to pass through it but restricts the
passage of other kinds of molecules. Membranes often permit the passage of solvent molecules and prevent
the passage of solute molecules. This is important in both cooking, and in of food and nutrients being
processed and used within your body.
OSMOSIS
is the movement of fluid across a
semipermeable cell membrane so
that there is an equal
concentration of solute on both
sides of the membrane.
In osmosis, the solvent can cross the membrane barrier,
but the solute is too large to cross. Solvent continues to
cross the membrane until the concentrations of the
solutions equalize.
Here are some ways osmosis is related to food:
Plants absorb water from the
ground, but also lose it
through their leaves.
Foods can become wilted or
dried out if water is allowed
to evaporate from them.
Cells absorb fluids through their
cell walls
Sugar or salt will pull juices out
of a food, to its surface.
Osmosis/diffusion video;; http://www.teachertube.com/video/osmosis-amp-diffusion-138155
Water and other liquids filter
through the large intestine
and are reabsorbed during
digestion.
Many foods quickly become
soggy exposed to liquids.
Some even lose their crunch
if exposed to the moisture in
the air for very long.