iGCSE Organic Chemistry - DA

Edexcel Double Award

What is the definition of a hydrocarbon?

A chemical compound composed of carbon and hydrogen ONLY.

What is fractional distillation?

A separation technique used to separate a mixture of liquids into different fractions by their boiling point.

What are the fractions in a fractionating column from top to bottom?

Refinery gases, gasoline, kerosene, diesel oil, fuel oil, bitumen.

As you go down the fractionating column, what happens to boiling point and hydrocarbon chain length?

Boiling points get HIGHER and the length of the carbon chain gets LONGER.

What happens to intermolecular forces, viscosity, and boiling point as the hydrocarbon chain gets longer?

Intermolecular forces increase, viscosity increases, boiling point increases.

What is the definition of boiling point?

The temperature at which a liquid turns into a gas.

What is the definition of volatility?

How easily something evaporates.

What is the definition of viscosity?

How easily something flows.

What is the definition of flammability?

How easily something burns.

What is an alkane?

A group of saturated hydrocarbons.

What is the general formula for an alkane?

CnH2n+2.

What is the mnemonic to remember the naming order of the first 4 alkanes?

Monkeys Eat Peanut Butter (Meth, Eth, Prop, But).

What is an isomer?

Molecules that have the same molecular formula but different structural arrangement of atoms.

What is a displayed formula?

Illustrates the arrangement of atoms for each element in space and includes the bonds between atoms.

What is a molecular formula?

A formula that shows the actual number of atoms for each element in a compound.

What is a homologous series?

A family of hydrocarbons with similar chemical properties who share the same general formula.

What features do molecules in a homologous series share?

Same general formula, same chemical properties, trend in physical properties, each member differs by –CH2, and shares a functional group.

What is combustion?

When a fuel (hydrocarbon) reacts with oxygen to produce carbon dioxide and water.

What are the two products of complete combustion?

Carbon dioxide and water.

What is a substitution reaction?

When an atom in a compound is replaced by another atom.

What is needed for halogenation of an alkane to occur?

UV light.

What color change occurs when methane reacts with bromine under UV light?

The mixture turns from orange to colourless.

What is cracking?

The thermal decomposition of a long chain hydrocarbon into small chain molecules.

What catalyst and temperature is needed for cracking?

Alumina and around 600-700 °C.

Why do we crack long chain hydrocarbons?

Small chain hydrocarbons are more useful, and we have a surplus of long chain hydrocarbons.

What is thermal decomposition?

When heat is used to break down a compound, with one reactant and many products.

What does saturated mean?

The hydrocarbon only contains single carbon bonds.

What is the general formula for an alkene?

CnH2n.

Why are alkenes unsaturated?

They contain a double bond between two carbon atoms.

How can you test if a substance is an alkane or an alkene?

Add bromine water; if it stays yellow - alkane, if it turns colourless - alkene.

What is incomplete combustion and why does it happen?

When a fuel burns in insufficient oxygen, producing carbon monoxide, which is toxic.

Why is carbon monoxide toxic?

It stops blood cells from transporting oxygen efficiently.

What is a polymer?

A long chain molecule made from monomers.

What is a monomer?

A small molecule that can be joined to another monomer to make a polymer.

As the chain of a hydrocarbon gets longer, what happens to the viscosity?

It becomes more viscous

As the chain of a hydrocarbon gets longer, what happens to its flammability?

It becomes less flammable

As the chain of a hydrocarbon gets longer, what happens to its colour?

The colour gets darker (yellow to brown to black)

As the chain of a hydrocarbon gets longer, what happens to the intermolecular forces between the chains?

The intermolecular forces get stronger

As the chain of a hydrocarbon gets longer, what happens to its boiling point?

The boiling point increases as the chain gets longer

Why are alkenes useful?

They can be made into polymers

What is structural formula?

A structural formula displays the atoms of the molecule in the order they are bonded. e.g Hexane is CH₃CH₂CH₂CH₂CH₂CH₃