Topic 1 of 8 · Form 3
States of matter and experimental techniques
Kinetic particle theory: arrangement, motion and energy of particles in solids, liquids and gases; changes of state (melting, boiling, evaporation, condensation, freezing, sublimation); diffusion – lighter gas molecules diffuse faster.
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States of matter
Kinetic particle theory: arrangement, motion and energy of particles in solids, liquids and gases; changes of state (melting, boiling, evaporation, condensation, freezing, sublimation); diffusion – lighter gas molecules diffuse faster.
Measurement
Apparatus for time, temperature, mass and volume (burettes, pipettes, measuring cylinders, gas syringes).
Purity
Pure substances have sharp melting and boiling points; impurities lower the melting point and raise the boiling point.
Separation techniques
Filtration, crystallisation, simple distillation, fractional distillation (crude oil, liquid air), and paper chromatography.
- Rf value = distance moved by substance ÷ distance moved by solvent front.
Worked example: A spot moves 3.6 cm while the solvent moves 9.0 cm. Find the Rf value.
Rf = 3.6 ÷ 9.0 = 0.40
- Locating agents reveal colourless spots (e.g. ninhydrin for amino acids).
Check yourself
- How does an impurity affect the melting point of a substance?
- Which technique separates ethanol from water?
- Why does ammonia diffuse faster than hydrogen chloride?
Show answers
- It lowers it and makes it melt over a range.
- Fractional distillation.
- Ammonia molecules have a lower relative molecular mass, so they move faster.
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