Developing Fuels
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State the standard conditions.
• Standard temperature - 25°c (298K) • Standard pressure - 1atm • Standard concentration - 1 mol dm-3 • Standard state - s,l,g
Define system
The reactants + products being measured (inside the reaction vessel)
Define surroundings
Everything else that’s not the system - outside the reaction vessel
Define exothermic
A reaction that gives out energy from the system to the surroundings and heats them.
Define endothermic
A reaction that takes energy into the system from the surroundings, cooling the surroundings.
What is thermochemistry?
The study of the energy + heat associated with chemical reactions.
Why type of process is bond breaking?
Endothermic as it requires energy
What type of process is bond forming?
Exothermic as energy is released
What formula is used to measure enthalpy change?
E = mcΔT
What do experiments to measure enthalpy changes ususally involve?
Transfering energy to/from water
What general formula can be used to calculate ΔH of a reaction?
ΔH = Hproducts - Hreactants
What is an alkane?
A saturated hydrocarbon
What are the 4 main features of alkanes?
Have the general formula CnH2n+2 Have names ending in -ane Are saturated - each C is bonded 4 times with the maximum number of hydrogens possible. Are aliphatic - don’t contain benzene rings
What do dashed/dotted bonds represent in the 3D structure of a molecule?
A bond in the direction behind the plane of the paper
What do wedges represent in the 3D structure of a molecule?
A bond in the direction in front of the plane of the paper
What does aromatic mean?
An organic molecule/hydrocarbon containing 1+ benzene rings
What does aliphatic mean?
Straight unbranched non-aromatic chains.
What is a functional group?
A modifier responsible for the characteristic chemical reactions/behaviours of molecules that contain it
What is a homologous series?
Series of compounds in which all members have the same functional group but have different carbon chain lengths
What is a cycloalkane?
A saturated hydrocarbon where the carbon atoms are joined in a ring
What are the 5 main features of a cycloalkane?
Have the general forumla CnH2n Have names begining with cyclo- Have names ending in -ane Are saturated - 2 hydrogens per carbon Are aliphatic
What is an alkene?
An unsaturated hydrocarbon containing 1+ C=C bonds
Describe the bonding in an alkene
A C=C bond contains a sigma (σ) bond and a pi (π) bond. A σ bond is an area of increased e- density between the C atoms. Only contains 1 area of negative charge A π bond consists of 2 areas of negative charge. One of these is above the line of the atoms and the other is below
What are the 5 main features of alkenes?
Have the general formula CnH2n (for 1 double bond) Have names ending in -ene Are unsaturated - Have 1+ double covalent bonds between C atoms in molecule Are aliphatic - don’t contain benzene rings Double bonds have a high electron density making alkenes fairly reactive.