Chapter 6 Separation and identification of the components of mixtures | Chemistry for VCE Units 1 & 2

solubility

the ability of a substance to dissolve

solute

the substance being dissolved in the solvent

solvent

the substance that another is being dissolved in, e.g. water

dissolve

when solute–solute bonds break and the solute molecules mix evenly with the solvent molecules

chromatography

an analytical technique that separates the components of a sample mixture based on the properties of the molecules

phase

(in chromatography) a form of matter that has uniform chemical and physical properties; can be a pure substance or a mixture

mobile phase

the solvent phase that flows, moving the components of a sample over the stationary phase

stationary phase

the solid phase to which the components of a sample are adsorbed; can sometimes be a liquid coated onto a solid support

affinity

the strength of the interaction of a substance within a sample with the mobile or stationary phase

adsorption

the attraction of a substance within a sample to the stationary phase; how the substance 'sticks' to the stationary phase

desorption

the release of a substance within a sample from the stationary phase into the mobile phase; how the substance 'unsticks' from the stationary phase

paper chromatography

an analytical technique for separating and identifying mixtures; the stationary phase is a thin strip of absorbent paper

origin

the line applied to a chromatogram to mark the point where the sample or standard is placed

capillary action

the movement of a liquid through a narrow space (e.g. the cellulose network in absorbent paper) without any help; usually against gravity

solvent front

the point the mobile phase reached on a chromatogram before the analysis is terminated

chromatogram

the pattern of bands, spots or peaks formed on the chromatograph paper or TLC plate, demonstrating the separation of a mixture

retardation factor (Rf)

the ratio of the distance travelled by a component of a sample, from the origin, in relation to the distance travelled by the mobile phase

thin-layer chromatography (TLC)

an analytical technique for separating and identifying mixtures; the stationary phase is typically a thin layer of silica gel, aluminium oxide or cellulose supported on a piece of glass or plastic

fluorescent

emitting visible light when exposed to radiation

two-dimensional paper or thin-layer chromatography

an analytical technique used to separate components; a first paper or thin-layer chromatography analysis is completed, and the sheet is rotated 90° and a second analysis is run using a different mobile phase

column chromatography

a technique used to separate and purify individual components from mixtures of compounds

separation science

the science of separating a mixture on the basis of the different properties of its components

column

the tube-like structure that contains the stationary phase in column chromatography, through which the mobile phase and sample flow

elute

come out of the bottom of a chromatography column

retention time (Rt)

the time that a component is retained by a chromatography column

high-performance liquid chromatography (HPLC)

a form of column chromatography in which the mobile phase is pumped through a column at a controlled flow rate; the particles of the stationary phase are much smaller than in column chromatography and are densely packed to make separation more sensitive and efficient

mass spectrometry

an analytical technique in which a sample is bombarded with electrons to form charged fragments; the fragments are analysed and put together like a puzzle to identify the substances present