Separation and filtration Flashcards
What is the difference between ‘pure’ in chemistry and everyday use?
‘Pure’ in chemistry means a single substance; in everyday language, it means a substance with nothing added to it.
What defines a mixture in chemistry?
Consists of 2 or more substances not chemically combined.
How do the chemical properties of substances in a mixture behave?
They remain unchanged in a mixture.
What is a pure substance?
A single element or compound, not mixed.
How can melting point data distinguish pure substances from mixtures?
Pure substances have a sharp melting point.
What do mixtures do in terms of melting and boiling points?
They melt over a range of temperatures.
What are the techniques for separating mixtures?
- Simple distillation
- Fractional distillation
- Filtration
- Crystallisation
- Paper chromatography
What is fractional distillation used for?
To separate a pure liquid from a mixture.
How does fractional distillation work?
It separates liquids with different boiling points.
What is a common use of fractional distillation?
Separating ethanol from water.
What happens to ethanol during fractional distillation?
Ethanol evaporates first due to lower boiling point.
What is the sequence of events in distillation?
- Heating
- Evaporating
- Cooling
- Condensing
What is simple distillation used for?
To separate a solvent from a solution.
How does simple distillation work?
Solvent vapor evaporates and is condensed.
What happens to the remaining solution during simple distillation?
It becomes more concentrated in solute.
What is the purpose of filtration?
To separate insoluble particles from a solution.
What is crystallisation used for?
To separate soluble salts from a solution.
What is the first step in crystallisation?
Warm the solution to evaporate the solvent.
What happens after warming the solution in crystallisation?
Allow the solution to cool for crystal growth.
What is paper chromatography used for?
To separate mixtures and identify substances.
What are the phases involved in chromatography?
- A stationary phase
- A mobile phase
How does separation occur in chromatography?
Based on the distribution of substances between phases.
What is the formula for Rf value?
Rf = distance moved by substance / distance moved by solvent.
How do different compounds behave in chromatography?
They have different Rf values in different solvents.
