States of matter, particle theory and purification Mr.H Unit 1.1-1.9 States of matter, particle theory and purification Mr.H

1.1 states of matter Atom: is the smallest particles that cannot be broken down by chemical means. Molecule: is a particle of two or more atoms joined together (e.g. H2, O2, CO2 ) Ion: is an atom that carries a charge, because it lost, or gained electrons (e.g. Na )

States of matter

1.2 Changing states

When a solid is heated, its atoms vibrate faster about their fixed points. The relative increase in the size of solids when heated is therefore small. Metal railway tracks have small gaps so that when the sun heats them, the tracks expand into these gaps and don’t buckle.

Liquids expand for the same reason, but because the bonds between separate molecules are usually less tight they expand more than solids. This is the principle behind liquid-in-glass thermometers. An increase in temperature results in the expansion of the liquid which means it rises up the glass.

Molecules within gases are further apart and weakly attracted to each other. Heat causes the molecules to move faster, (heat energy is converted to kinetic energy) which means that the volume of a gas increases more than the volume of a solid or liquid.However, gases that are contained in a fixed volume cannot expand - and so increases in temperature result in increases in pressure.

Note that during a change in state, the line is flat, because the energy is not going to raising the temperature, but rather into breaking the bonds (or forming them)

1.3 Kinetic particle theory Particles in gases and liquids move randomly Particles in gases do not attract each other Particles in gases are so tiny that their volumes can be ignored When particles in gases collide they bounce off each other without any overallenergy change.

Brownian motion Particles in both liquids and gases (collectively called fluids) move randomly. This is called Brownian motion. They do this because they are bombarded by the other moving particles in the fluid. Larger particles can be moved by light, fast-moving molecules.

Unit 1.4

The white ring forms nearer the HCL because the hydrogen chloride is heavier than the ammonia

1.5 Apparatus for measuring

Measuring gas volume by displacement of water

To insure experimental accuracy Repeat your measurements in the same way each time Use apparatus with small scale division Use apparatus carefully

1.6 Chromotography Chromatography can be used to separate mixtures of coloured compounds. Mixtures that are suitable for separation by chromatography include inks, dyes and colouring agents in food.

Chromatogram shows different dyes

Rf (retention factor) values Different chromatograms and the separated components of the mixtures can be identified by calculating the Rf value using the equation: Rf = distance moved by the compound ÷ distance moved by the solvent The Rf value of a particular compound is always the same - if the chromatography has been carried out in the same way. This allows industry to use chromatography to identify compounds in mixtures.

1.7 Purity of chemicals Purity is very important e.g. for analytical standards in laboratories or pharmaceutical products where impurities could have dangerous side effects in a drug or medicine. Purity is also important for anything ingested by the body (including foods and drink)

Melting point and boiling point The purity of a compound can be established using data from its melting point or boiling point and from thin layer chromatography. Impure compounds have a range of melting points and boiling points, as the different substances they contain melt or boil at different temperatures. They may even interfere with each other's melting and boiling points. On the other hand, pure compounds have definite melting points and boiling points. The presence of an impurity usually: Lowers the melting point Raises the boiling point The greater the amount of an impurity, the bigger the differences from the true melting point and boiling point.

1.8 Methods of purification Filtration Decanting Centrifugation Evaporation Fractional distillation Crystallisation Solvent extraction

What is Filtration? Filtration is a separation technique that is used to separate a solid that has not dissolved in a liquid (for example a precipitate).

What is decanting? to pour a liquid gently so as not to disturb the sediment.

Centrifugation Centrifugation is the process where a mixture is separated through spinning. It is used to separate skim milk from whole milk, water from your clothes, and blood cells from your blood plasma. Although centrifugation is primarily used to separate mixtures

Fractional distillation

Crystallisation Crystallisation is a separation technique that is used to separate a solid that has dissolved in a liquid and made a solution. The solution is warmed in an open container, allowing the solvent to evaporate, leaving a saturated solution.

Solvent extraction Liquid–liquid extraction also known as solvent extraction and partitioning, is a method to separate compounds based on their relative solubilities in two different immiscible liquids, usually water and an organic solvent. It is an extraction of a substance from one liquid into another liquid phase.

1.9 simple distillation

Separating Sand and Salt. Steps.