Unit 2 i) Hydrocarbons Flashcards
Name the 3 fossil fuels?
Coal Oil Gas
Fossil fuels are finite. What does finite mean?
This means that they will eventually run out
What is combustion?
Combustion is a chemical reaction where substances burn in the presence of oxygen
What word is used to describe a reaction that gives out heat?
Exothermic
What is an endothermic reaction?
A reaction that takes in energy.
What is a fossil fuel?
Fuel from remains of long dead animals or plants. eg coal oil gas
What is the test for hydrogen?
Burns with a pop
What is the test for oxygen?
Relights a glowing splint
What is the test for carbon dioxide?
Turns lime water milky
What is a hydrocarbon?
A substance that contains only hydrogen and carbon
What is the simplest alkane?
Methane
What is the general formula of the alkanes?
CnH2n+2
What is a fuel?
A fuel is a substance which has stored energy. This energy is released when a fuel is burned
What is made when alkanes burn in excess oxygen?
Carbon dioxide and water
Name the alkanes and formulas from 1 to 8 carbons
Methane CH4 Ethane C2H6 Propane C3H8 Butane C4H10 Pentane C5H12 Hexane C6H14 Heptane C7H16 Octane C8H18
What do all alkenes contain?
A carbon to carbon double bond
What is the simplest alkene?
Ethene C2H4
What is the general formula for the alkenes?
CnH2n
Name the alkenes and formulas for 1 to 8 carbons
Ethene C2H4 Propene C3H6 Butene C4H8 Pentene C5H10 Hexene C6H12 Heptene C7H14 Octene C8H16
How are the carbon to carbon bonds in cycloalkanes?
All single
What are isomers?
Isomers are substances with the same molecular formula but different structural formula eg cycloalkanes and alkenes
What is the general formula for cycloalkanes?
CnH2n
What does saturated mean?
All bonds are single
How do you test for unsaturation?
To test if a hydrocarbon has double bonds we use bromine water. When bromine water is shaken with an unsaturated hydrocarbon the brown colour disappears
What is crude oil?
Crude oil is a mixture of many hydrocarbon molecules
What is distillation?
Distillation is two processes: evaporation followed by condensation
What are the fractions when crude oil is distilled?
Fuel gases C1-C4 Petrol C8 Paraffin - jet fuel Diesel C16 - lorries and buses Bitumen
As you go down the fractions what happens?
Molecular size increases Boiling point increases Viscosity increases Ignition temperature increases
What process breaks down large molecules into smaller molecules?
Thermal cracking
What is thermal cracking?
Breaking bonds to convert large molecules into smaller ones
What is the shape of this?
Tetrahedral
What is the shape of ammonia?
Pyramidal
