C-8 Chemical Analysis
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What is a pure substance
• A pure substance is a single element or compound not mixed with any other substance
What is a quality of a pure substance
• Melt and boil at specific temperatures
What can be used to determine pure substance
• Melting point • Compare to mixtures _ closer to boiling point the more pure
What effect do impurities have on mixtures qualities
• Effect meting and boiling point • Low melting point and increased melting range • Increased boiling point- increased boiling range
• What is purity in everyday language
• A pure substance is one without anything added to it E.g Pure Milk
What is a formulation
• A formulation is a mixture that has been designed with a useful product
What are the products of formulations
Complex mixtures in which each chemical has a specific purpose
How are formulations made
• Mixing compounds carefully messed carefully to ensure properties of product- • e.g medicine and its shell life and its curing properties
What are some example of formations
• Fuels • Cleaning agents • Medecine • Paints • Alloys • Food • Fertiliser
How are compounds identified
• Will have ratios or percentages of each product which gives indication
What can chromatography be used for
• Used to separate mixtures and give help identifying substances
• What does chromatography involve
• Stationary and mobile phase
What is a stationary phase
• Where molecules can’t move- solid or thick liquid
What is a mobile phase
• Where molecules can move- liquid or gas
What does separation depend on
• Distribution of substances between phases- whether it spend more tim win stationary or mobile phase
What is the calculation for the Rf value
• Distance moved by substance // Distance moved by solvent
How does chromatography work
• Constantly move between mobile and stationary phase • Mobile phase moves through stationary phase- anything dissolved in mobile phase moves through it • Chemicals that spend more time in mobile phase move further • As they spend different amounts of time in mobile phase they move and end at different points
What happens to pure substances in chromatography
• Pure substances won’t separate
• What does the amount of time spent in the mobile phase depend on
• Solubility- more time in mobile phase move further- - How attracted to paper- wills pend more time in mobile phase
How can you test for pure substances in a mixture
• Get mixture and known pure substances and run chromatography • Compare distances of spots and if two Rf values match up- pure substance may be present • Test in other solvent to make sure
• What is the test for chlorine
• Chlorine bleaches damp litmus paper white
• What is the test for oxygen
• Put glowing split into test tube of oxygen- if relights- oxygen is present
• What is the test for carbon dioxide
• Bubbling or shaking through calcium hydroxide- limewater- it will go cloudy
What is the test for hydrogen
• Lit splint at end of test tube- squeaky pop