Chemistry - Structure 1: Models of the particulate nature of matter.

Atom

The smallest unit of an element, consisting of protons, neutrons, and electrons, and retaining the chemical properties of that element.

Elements

Pure substances that cannot be broken down into simpler substances by chemical means, consisting of only one type of atom.

Compounds

Substances formed from two or more elements chemically bonded in fixed proportions. Represented by chemical formulas.

Pure substances

Matter that has a uniform and definite composition, including elements and compounds.

Mixtures

Substances made up of two or more different elements or compounds that are physically combined with no fixed proportions, retaining their individual properties.

Homogenous

A mixture with uniform composition and properties throughout requires the intermolecular forces within the different components to be similar in nature.

Heterogenous

A mixture with a non-uniform composition with particles throughout that differ in properties. Interactions between the components vary, and components may be distinguished from one another by observation.

Filtration

A physical separation technique which uses a filter medium to remove solid particles from a liquid or gas. The solid is collected as a residue, whereas the filtrate, containing the solvent, passes through the filter paper.

Distillation

A physical separation technique which incorporates separating the individual components of a liquid mixture of two or more chemically discrete substances according to their boiling points.

Reflux

Process of heating a reaction mixture to a stable boiling point without any loss of solvent or reactant.

Evaporation

A physical separation technique applied to separating mixtures through heating the solution in an evaporating dish, prompting the solvent to evaporate and the solute to remain.

Solvation

Process where solvent molecules interact with and surround a dissolved solute, forming stable complexes through weak, non-covalent forces.

Recrystallisation

A purification process for solid compounds that exploits differences in solubility to separate a desired product from impurities.

Paper chromatography

Analytical process for separating and identifying the components of a mixture by exploiting differences in their polarity and solubility.

Thin layer chromatography

Uses a thin layer of Al₂O₃ or Silica SiO₂ on an unreactive support such as glass; components can be recovered pure.

Diffusion

Distribution of particles, due to the random motions.

Volatile

Easily evaporated at normal temperatures.

Absolute zero

Theoretically lowest possible temperature at which a system's particles would stop their thermal motion, equaling 0 Kelvin (K), -273.15 degrees Celsius (°C).

Temperature

Measure of the average kinetic energy of the particles.

Sublimation

Direct physical change from solid to gas due to the indistinguishability in the melting and boiling points (endothermic reaction).

Deposition

Direct physical change from gas to solid, due to the indistinguishability in the condensing and freezing points (exothermic reaction).

Vaporization

The state change from liquid to gas, may occur in two processes: boiling and evaporating

Boiling

Takes place at a fixed temperature when the vapor pressure is equal to the external pressure. Lower external pressure requires lower vapor pressure and the boiling occurs at a lower temperature.

Evaporation

Takes place at a range of temperatures below the boiling point and is a slow, surface-level process.