C1c Smells


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C1c Smells

  1. 1. C1c Smells • We use chemicals that smell nice as perfumes • A family of chemicals that often smell nice is called the esters. • Some esters occur naturally in plants e.g. oranges and lemons • Natural esters can be extracted from the plants that make them and used in perfumes (we will investigate this further in C4f). • Esters can also be manufactured synthetically by chemists. They are used to enhance food flavourings e.g. pear drops are made from synthetic esters How are esters made? Esters are made by reacting a carboxylic acid and an alcohol together. warm Method: 1. Put equal amounts of carboxylic acid and alcohol in a test tube e.g. 10cm3 of each 2. Add 1cm3 of sulfuric acid (as a catalyst) and warm the mixture gently for 5 minutes. 3. Tip the mixture into 100cm3 of sodium carbonate solution to neutralise the acid. 4. Distil to separate off the ester. e.g. butanol + ethanoic acid Higher only ethanol + ethanoic acid ethanol + propanoic acid + propanoic acid butyl propanoate propanol + propyl ethanoate
  2. 2. What properties must a perfume have? • Perfumes have a pleasant smell. • They smell because they stimulate sense cells in the nose • There are 5 physical properties that perfumes must have: 1. 2. 3. 4. 5. Higher Volatility of Perfumes and Intermolecular Forces • Why do the particles stay together in a liquid?  All particles/molecules are _____________ to each other. solid  Solids - the attractions are very strong and the particles are close together. liquid  Liquids - the attractions are weaker so they can flow over each other and  Gases - the attraction between particles is very weak so they are a long gas way apart  We call these forces of attraction between particles _____________________________________ • Perfumes need to evaporate at body temperature. This is quite a low temperature so they must be ___________________. • What does volatile mean? A liquid that is volatile ____________________ easily i.e. the more volatile a liquid is, the faster it evaporates. Summary 1. Perfume molecules (esters) have weak intermolecular forces. 2. Body temperature is enough to break these forces of attraction 3. The perfume molecules evaporate from the skin and diffuse to sense cells in the nose
  3. 3. Solvents solute + solvent solution • Water is known as the “universal solvent” because it dissolves many solids. • All of the cells in your body contain water and the chemical reactions in those cells all take place in aqueous solution. • But not all solids dissolve in water e.g. nail varnish. • So we have to find alternative solvents • ______________, _____________ and _________ can be used as solvents • The more of a solute (solid) you can dissolve in a solvent, the more soluble that solute is. e.g. Solute A Solute B Solute C 10g of solute A 5g of solute B 0g of solute C dissolves in 100cm3 of dissolves in 100cm3 dissolves in 100cm3 water of water of water Which of these solutes is more soluble? Explain your answer. Which of these solutes is insoluble in water? Suggest an alternative solvent. Higher Explain why nail varnish will not dissolve in water 1. 2.
  4. 4. “Is the testing of cosmetics on animals justified?” • Cosmetics must be tested to ensure that they are __________ to use e.g. they must not be ___________, react with __________ or ___________ the skin • They cannot be sold unless they have been __________ in some way • Some cosmetics are tested on ______________. You must be able to explain advantages and disadvantages of testing on animals. You should develop your own ideas but here are some examples: Advantages – Disadvantages –