Glossary of terms

Anion

A negatively charged ion

Anode

The electrode at which oxidation occurs in a cell. Anions migrate to the anode.

Boiling Point

The temperature at which the vapor pressure of a liquid is equal to the external pressure on the liquid.

Cathode

The electrode at which reduction occurs. Cations migrate to the cathode

Cation

A positively charged ion

Chemical Potential

Free energy change per mole of a specific reactant

Colligative Properties

Properties of a solution which depend on the number of solute molecules present but not on the nature of the solvent. Examples are osmotic pressure, vapor pressure,freezing point depression and boiling point elevation.

Corrosion

Oxidation of a metal.

Dialysis

The selective passage of ions and small molecules, over proteins.

Electrochemical Potential

Free energy change per mole of electrons transferred.

Electrolysis

The passgae of a strong electric current through a molten ionic compound resulting in decomposition of compound into its elements, eg NaCl into Sodium metal and Chlorine gas

Electrostatic

Interactions arising due to partial or whole charges on neighbouring atoms or molecules

Equilibrium

Dynamic equilibrium is established when two opposing forces are occuring at the same rate, so there is no apparent change in the system over long periods of time.

Free Energy

Energy that is available to do useful work. A decrease in free energy accompanies any spontaneous process.

Freezing Point

When the processes of freezing and thawing are in equilibrium

Galvanise

Zinc plating a metal which has a less negative reduction potential will protect the metal as the zinc is oxidised in preference. This is called galvanising

Hydrogen Bonds

Weak ionic attraction formed when a hydrogen atom carrying a partial positive charge is near a small O, N or F atom which is carrying an excess negative charge

Molality

Concentration measured as moles of solute per kilogram of solvent.

Molarity

Concentration measures as moles of solute per litre of solution

Mole

An amount equal to the number of carbon atoms in exactly 12 grams of the C12

Mole fraction

Concentration of a substance in a mixture measured as moles of the substance per mole of complete mixture.

Osmosis

Passage of solvent molecules from a dilute solution through a semipermeable membrane to a more concentrated solution

Osmotic Pressure

Pressure which must be applied to a solution to prevent water from flowing in via a semi-permeable membrane

Oxidation

The loss (or partial loss) of one or more electrons by an atom, molecule or ion.

Partial Pressure

The partial pressure of a gas is the pressure that it would exert if it occupied the container alone.

Polar and Nonpolar

Polar molecules have an uneven charge distribution over their surface as the bonding electron pair sit closer to one atom than the other, one example is Water. Nonpolar molecules have an even charge distribution such as methane.

Porous

Having microscopic holes that allow the passage of small particles.

Reduction

The gain (or partial gain) of one or more electrons by an atom, molecule or ion.

Reduction Potentials

The reduction potential for any substance is the cell reaction for theat substance in combiination with the Standard Hydrogen Electode.

Semipermeable membrane

A membrane that allows some but not all of the components in a mixture to pass through it. Semipermeable membranes are used in dialysis.

Spontaneous

Spontaneous processes do not require work to be done in order to occur.

Van der Waals attractions

These are interactions between molecules which leave their chemical identis unchanged such as the interactions between the partial charges on polar molecules.

Vapor Pressure

The vapor pressure of a liquid is the pressure above the liquid when the liquid and vapor phases are in dynamic equilibrium.

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