key definitions according to the course specifications Flashcards
groups
vertical columns within the table containing elements with similar chemical properties resulting from a common number of electrons in the outer shell
periods
rows of elements arranged wih increasing atomic number, demonstrating an increasing number of outer electrons and a move from metallic to non-metallic characteristics.
covalent radius
measure of the size of an atom
first ionisation energy
the energy required to remove one mole of electrons from one mole of gaseous atoms
second and subsequent ionisation energies
the energies required to remove further moles of electrons
electronegativity
a measure of the attraction an atom involved in a bond has for the electrons of the bond
covalent bond
a result of two positive nuclei being held together by their common attraction for the shared pair of electrons
polar covalent bonds
formed when the attraction of the atoms for the pair of bonding electrons is differnet
van der waals forces
the intermolecular forces acting between molecules. several different types of these including london dispersion forces, permanent dipole-permanent dipole which include h ydrogen bonding
london dispersion forces
forces of attraction operating between all atoms and molecules. much weaker than all other types of bonding. formed as a result of the electrostatic attraction between temporary dipoles and induced dipoles caused by movement of electrons in atoms and molecules
polar molecule
a moment is described this way if it has a permanent dipole
permanent dipole-permanent dipole interactions
additional electrostatic forces of attraction between polar molecules
hydrogen bonds
electrostatic forces of attraction between molecules that contain highly polar bonds of hydrogen bonded to oxygen, nitrogen or fluorine.
reduction
gain of electrons by a reactant in any reaction
oxidation
loss of electrons by a reactant in any reaction
oxidising agent
a substance that accepts electrons
reducing agent
a substance that donates electrons
the electrochemical series
represents a series of reduction reactions
saturated compounds
ones containing only single C-C bonds
unsaturated compounds
ones containing at least one C=C bond
addition reactions
in these reactions, two molecules combine to form a single molecule
isomers
these are compounds with the same molecular formula but different structural formulae. they may belong to different homologous series and they usually have different physical properties
volatility
ease of evaporation
alcohol
a molecule containing a hydroxyl functional group
primary alcohol
the hydroxyl group is attached to a carbon that has two hydrogens attached to it and 1 carbon
secondary alcohol
hydroxyl group is attached to a carbon that is attached to 2 carbons and a hydrogen
tertiary alcohol
hydroxyl group is attached to a carbon that is attached to 3 other carbons
diols
alcohol containing two hydroxyl groups
triols
alcohols containing three hydroxyl groups
carboxylic acid
a molecule containging the carboxyl functional group
ester
a molecule containing an ester link. these are used as flavourings and fragrances and many have pleasant, fruity smells.
condensation reaction
reaction where two molecules are joined together with the elimination of a small molecule
hydrolysis
a molecule reacts with water to break down into smaller molecules
edible fats and oils
esters formed from the condensation reaction of glycerol and three carboxylic acid molecules
fats and oils are…
a concentrated source of energy and essential for the transport and storage of fat-soluble vitamins in the body
soaps
ionic salts produced by the alkaline hydrolysis of edible fats and oils.
structure of soap
- long non polar hydrophobic tails
- hydrophilic negatively charged ionic heads
hard water
a term used to describe water containing high levels of dissolved metal ions
scum
insoluble precipitate formed when soap is used in hard water
emulsion
contains small droplets of one liquid dispersed in another
emulsifier
used to prevent non polar and polar substances separating into layers
proteins
major structural materials of animal tissue and are also involved in the maintenance and regulation of life processes.
enzymes
proteins which act as biological catalysts
amino acids
building blocks from which proteins are formed. relatively small molecules which all contain an amino group
essential amino acids
the amino acids required for protein synthesis that the body cannot make that must be acquired from the diet
denaturing
the denaturing of proteins in foods causes he texture to change when it is cooked.
oxidation (oxidation of food0
an increase in the oxygen to hydrogen ratio
reduction (oxidation of food)
decrease in the oxygen to hydrogen ratio
aldehydes and ketons
molecules containing the carbonyl functional group
rancidity
the oxidation of edible oils gives food a rancid flavour
antioxidants
molecules that prevent unwanted oxidation reactions occurring. they are easily oxidised and oxidise in the place of the compounds they have been added to protect. they can be identified as the substance being oxidised in a redox equation
essential oils
concentrated extracts of the volatile, non water soluble aroma compounds from plants
terpenes
key components in most essential oils. unsaturated compounds formed by joining together isoprene units
ultraviolet radiation
a high energy form of light, present in sunlight. UV light can provide sufficient energy to break bonds within molecules.
free radicals
free radicals are atoms or molecules that are highly reactive due to the presence of unpaired electrons
free radical chain reactions
involve the following steps; initiation, propagation, termination
initation
UV lights break bonds to form free radicals
propagation
free radicals collide with other species but the number of free radicals is maintained.
termination
free radicals can react with other free radicals and are used up
free radical scavengers
molecules that react with free radicals to form stable molecules and prevent chain reactions from occurring. they are added to many products including cosmetics, food products and plastics
factors influencing industrial process design
- availability, sustainability and cost of feedstocks
- opportunities for recycling
- energy requirements
- marketability of by-products
- product yield
environmental considerations of industrial process design
- minimising waste
- avoiding the use or production of toxic substances
- designing products which will biodegrade if appropriate
molar volume
the volume occupied by one mole of any gas at a certain temperature and pressure. it is the same for all gases at the same temperature and pressure
theoretical yield
the quantity of desired product obtained assuming the full conversion of the limiting reagent
actual yield
the quantity of desired product formed under the prevailing reaction conditions
atom economy
measures the proportion of the total mass of all starting materials converted into the desired product in the balanced equation
enthalpy change
the energy difference between the products and the reactants
activation energy
minimum energy required by colliding particles to form an activated complex. minimum kinetic energy required by colliding particles before a reaction may occur
activated complex
unstable arrangement of atoms formedat the maximum of a potential energy barrier during a reaction
catalyst
substance that provides an alternative reaction pathway with a lower activation energy
temperature
a measure of the average kinetic energy of the particles in a substance
exothermic
a reaction or process that releases heat energy
endothermic
a reaction or process that takes in heat energy
enthalpy of combustion of a substance
the enthalpy change when one mole of a substance burns completely in oxygen
Hess’s law
states that the enthalpy change for a chemical reaction is independent of the route taken
molar bond enthalpy
the energy required to break one mole of bonds in a diatomic molecule
mean molar bond enthalpy
the average energy required to break one mole of bonds, for a bond that occurs in a number of compounds
equibrium
at equilibrium, the concentrations of reactants and products remain constant, but are rarely equal.
chromatography
a technique used to separate the components present within a mixture
volumetric analysis
involves using a solution of accurately known concentration in a quantitative reaction to determine the concentration of another substance
titration
used to accurately determine the volumes of solution required to reach the end point of a chemical reaction
standard solutions
solutions of accurately known concentration are known as standard solutions
