What is a pure substance?
A single element or compound
How can you tell if a substance is pure?
It melts and boils at a specific temperature.
Why are melting and boiling points useful?
To distinguish pure substances from mixtures.
What is a formulation?
A mixture designed as a useful product.
Give examples of formulations.
Fuels
Why are formulations made carefully?
Each chemical has a specific purpose and is measured to give required properties.
What is chromatography used for?
To separate mixtures and help identify substances.
What are the two phases in chromatography?
Stationary phase and mobile phase.
What is the stationary phase?
The phase that does not move (e.g.
What is the mobile phase?
The phase that moves and carries the substances (e.g.
How does chromatography separate substances?
Substances distribute differently between stationary and mobile phases.
What is the Rf value?
Distance moved by substance ÷ distance moved by solvent.
How can chromatography identify pure substances?
Pure substances produce a single spot in all solvents.
What is the required practical for chromatography?
Paper chromatography to separate coloured substances and calculate Rf values.
What is the test for hydrogen?
Burning splint at the open end → pop.
What is the test for oxygen?
Glowing splint inserted → relights.
What is the test for carbon dioxide?
Bubble through limewater → turns cloudy.
What is the test for chlorine?
Damp litmus paper → bleaches white.
