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 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 eliminatedcarried 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 ppm26 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 semi-permeable 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 hormonesIodide (I-) – thyroid hormones

Phosphate (PO43-) - with Ca2+ in teeth and bone formation