Chemistry C8

  • Created by: abbiedye
  • Created on: 26-07-18 14:58

What is purity in chemistry?

  • In chemistry, a pure substance is something that only contains one compound or element throughout and is not mixed with anything else
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How do impurities effect melting/boiling points?

  • The boiling or melting point tells you how pure a substance is
  • Impurities - lower the melting point and increase the melting range
  • Impurities - increase the boiling point and may result in the sample boiling at a range of temperatures
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What are formulations?

  • Useful mixtures with a precise purpose - made by following a 'formula' (recipe)
  • Paints are formulations of: pigment, solvent, binder (resin) and additives
  • Important in the pharmaceutical industry and everyday life (cleaning products, fuels, cosmetics, fertilisers, metal alloys, food and drink
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The two phases of Chromatography

  • Mobile phase = where molecules can move, always a liquid or a gas
  • Stationary phase = where molecules can't move, can be a solid or a really thick liquid
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Equilibrium in Chromatography

  • The substances in the sample constantly move between the mobile and stationary phases - creating an equilibrium
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Distance traveled and dissolved substance

Rf = distance traveled by substance / distance traveled by solvent

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What is the test for chlorine?

  • Chlorine bleaches damp litmus paper, turning it white
  • (It may turn red for a moment first though, that is because a solution of chlorine is acidic)
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What is the test for oxygen?

  • If you put a glowing splint inside a test tube containing oxygen, the oxygen will relight the glowing splint
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What is the test for carbon dioxide?

  • Bubbling carbon dioxide (or shaking a carbon dioxide with) an aqueous solution of calcium hydroxide (known as limewater) causes the solution to turn cloudy
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What is the test for hydrogen?

  • If you hold a lit splint at the open end of a test tube containing hydrogen, you'll get a 'squeaky pop'
  • The noise comes from the hydrogen burning quickly with the oxygen in the air to form H2O
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