Alkane Basics
What elements do alkanes contain?
Carbon and Hydrogen only (Hydrocarbons)
What is the molecular formula of methane?
CH4
Are alkanes reactive or unreactive?
they are quite unreactive
Gases
What are structural isomers?
Compounds with the same molecular formula but different structures.
What kind of bonds do alkanes have?
Single covalent bonds
How many carbon atoms does propane have?
3
What happens when alkanes burn completely in oxygen?
they form carbon dioxide and water
What happens to the boiling points as the chain length increases?
Boiling points increase.
Give two examples of structural isomers mentioned in the text.
Butane and 2-methylpropane.
What is the general formula of alkanes?
CnH2n+2
Which alkane has the formula C4H10?
Butane
Write the word equation for the complete combustion of methane.
Methane + oxygen → carbon dioxide + water.
What are propane and butane used as when mixed together?
LPG (liquefied petroleum gas).
Which has a lower boiling point: butane or 2-methylpropane?
2-methylpropane.
What does it mean when we say acned are "saturated"?
They contain only single bonds between carbon atoms
Which alkane has a boiling point of -87 Celsius degrees?
Ethane
What are the products of incomplete combustion of methane?
Carbon monoxide and water.
What are the uses of LPG?
Used as fuel for heating and cooking.
Why does 2-methylpropane have a lower boiling point?
Branched-chain hydrocarbons have lower boiling points than straight-chain ones.
Alkanes from homologous series. What does this mean in terms of structure and chemical behaviour?
Each alkane differs by one CH2 group , showing gradual change in physical properties but similar chemical reactions
Using the boiling point pattern, predict which would have a higher boiling point — propane or pentane — and explain why.
Pentane, because longer chains have stronger intermolecular forces, requiring more energy to separate.
If an alkane has a high boiling point, how does that affect its usefulness as a fuel?
It’s less useful as a gas fuel because it condenses easily and doesn’t burn as readily as shorter-chain alkanes.
Why does burning alkanes release large amounts of energy compared to many other reactions?
Because strong C–H and C–C bonds are replaced by even stronger C=O and O–H bonds, releasing significant energy.
Why are branched-chain hydrocarbons preferred in racing car fuels, even though they have lower boiling points?
They burn more smoothly and are less likely to cause engine knocking, allowing better control of combustion.