Solutions, Suspensions and Emulsions
Liquid mixtures can be divided into 4 main types :
solutions, suspensions, colloids and emulsions
Solutions :
- consist of soluble
material or material
(solute) dissolved in
a liquid (solvent)
- are clear
- are homogenous
(one phase) and do
not settle
Suspensions :
- consists of non-soluble solids suspended in a
liquid medium
- not clear
- are heterogeneous (more than one phase) and
settle out
Emulsions :
- consists of liquid suspended in a liquid medium
- an emulsion that settles is called a temporary
emulsion
The Importance of Solutions
Digestion – food changed into soluble substances
so that it can be dissolved in the blood and
carried to other parts of the body
Waste products dissolve in the blood and are
carried to where they can be eliminated
Many chemical reactions will only occur in
solutions, for eg., AgNO3 and NaCl
Drugs are often given in a solution form
*Note : Dilute solution contains little solute.
Concentrated solution contains a lot of solute
Percentage solutions :
Mass-volume method – expresses the mass of
the solute in a given volume of solvent, usually
water, for eg., a 10 % glucose solution will contain
10 grams of glucose (solute) in 100 ml of water
(solvent). A 0.7 % glucose solution will contain
0.7 grams of glucose in 100 ml of water.
Milligram percent – number of milligrams (mg) of
solute in 100 ml of solvent
Parts per million (ppm) – milligrams of solute in one
litre of solvent, ie., 1 mg in 1 L = 1 ppm
26 mg in 1 dm3 = 26ppm (1 L = 1 dm3)
Diffusion – this is also known as passive transport.
It is a process whereby a substance moves from
an area of higher concentration to an area of
lower concentration, ie., down a concentration
gradient. No energy is required. Active
transport is when you put energy in and force
substances to move from an area of low
concentration to an area of high concentration
Osmosis – the diffusing substance is water. It is
defined as the diffusion of water through a semipermeable membrane from a weaker solution
(more water) to a stronger solution (less
water)
Isotonic solutions – these are solutions that have
the same solute concentrations, for eg., the
normal salt concentration in blood is 0.9 %. If a
NaCl solution (made in water) is given to a
patient, the semi-permeable red blood cells will
not be affected because the concentration is the
same inside and outside them so they do not
absorb or lose water.
Hypotonic solution – contains a lower solute
concentration than another solution, for eg., if a
red blood cell is placed in water, it will absorb
water by osmosis until it bursts.
So, a hypotonic solution
is not used for
transfusions.
Hypertonic solution – contains a higher solute
concentration than
another solution.
The reverse of the
above will occur.
Ions in the Body
Calcium (Ca2+) – blood clotting, bones, teeth and
muscle action
Iron (Fe2+) – haemoglobin
Sodium (Na+) – main extracellular positive ion
Potassium (K+) – main intracellular positive ion
Iodide (I-) – thyroid hormones
Phosphate (PO43-) - with Ca2+ in teeth and bone
formation