C1 - Fractional Distillation

What does fractional distillation separate?

A mixture of different liquids.

What must the liquids have for fractional distillation to work?

Different boiling points.

What is the key difference between simple and fractional distillation?

Fractional distillation uses a fractionating column.

What equipment is added in fractional distillation that simple distillation doesn't have?

A fractionating column containing glass beads.

What does the fractionating column do?

It increases the separation of liquids by repeated evaporation and condensation.

What happens when the mixture is heated?

Both liquids start to evaporate, but the one with the lower boiling point evaporates more easily.

What do the vapours do inside the fractionating column?

They condense and evaporate repeatedly as they rise.

What is the effect of repeated condensation and evaporation in the column?

It enriches the vapour with the substance that has the lower boiling point.

What happens when the vapour reaches the thermometer?

The temperature begins to rise.

What does it mean if the temperature on the thermometer is rising?

A mixture of vapours is passing over, but mostly the lower boiling point substance.

What happens when the temperature becomes constant (e.g. at 80°C)?

Only the lower boiling point substance is reaching the condenser.

What is collected when the temperature is stable at the lower boiling point?

A relatively pure sample (fraction) of the lower boiling point liquid.

What is done after collecting the first fraction?

The process continues until the temperature rises and stabilises at the higher boiling point.

What does it mean when the temperature rises again?

The second liquid is now evaporating and reaching the condenser.

What is collected when the thermometer shows the second boiling point (e.g. 100°C)?

A relatively pure sample of the second liquid.

What is the purpose of a condenser in fractional distillation?

To cool vapours and turn them back into liquids.

What is a "fraction" in fractional distillation?

A separated liquid component collected during the process.

What is an example of fractional distillation in industry?

Separating fractions of crude oil.

Why does fractional distillation work better when boiling points are very different?

Because it's easier to separate the liquids cleanly.

What happens if the liquids have similar boiling points?

The separation becomes harder and may require several distillations.

Can fractional distillation be used for large-scale separation?

Not with simple lab equipment; large-scale distillation is used in industry.

Why do the glass beads in the fractionating column help?

They provide a large surface area for vapour to condense on and evaporate again.

Why does the liquid with the lower boiling point reach the top of the column first?

Because it turns into vapour more easily.

How does the thermometer help in fractional distillation?

It shows when a substance with a specific boiling point is reaching the top of the column.

Why is cold water run through the condenser?

To cool down the vapours so they condense into a liquid.

What is meant by "boiling point"?

The temperature at which a substance changes from liquid to gas.

What is a mixture?

Two or more substances not chemically bonded, which can be physically separated.

What does the temperature tell us during fractional distillation?

Which substance is evaporating and being collected at that moment.

What happens if you collect a liquid while the temperature is still rising?

You get a mixture, not a pure substance.

When is the best time to collect each liquid?

When the thermometer reading stays constant at its boiling point.

What is a limitation of fractional distillation in a lab setup?

It's not suitable for separating large volumes of liquid.

What property of a substance does fractional distillation rely on?

The boiling point of each substance.