4. The NEED for pure substance In pharmaceutical industry, medicines must be tested for purity before they are sold. Impurities in drugs and food may produce undesirable side effects.
6. The NEED for pure substance In food and beverage industry, the types of chemicals which can be added into our food are controlled by certain governmental guidelines to ensure that our food and drinks contain chemicals that are safe for consumption.
9. Criteria for purity Mixtures Pure Substances Properties Boiling Point Melting Point Exact and Fixed Not Fixed (Higher) Not Fixed (Lower) Definite Not Definite Exact and Fixed
12. A pure substance contains only one type of substance (that is, one type of molecule or atom) Melting point of pure water = 0 ºC Boiling point of pure water = 100 ºC So, do you think the temperature for sea water is also 100 ºC?
16. Some important terms Some terms that you should know: A solute is a dissolved substance (e.g. salt in salt solution). A solvent is a substance which dissolve a solute (e.g. water in salt solution. Miscible liquids are liquids that are completely soluble in each other.
21. Types of separation techniques Suitable method of purification: Filtration Aim: To separate a soluble and insoluble solid (E.g. Salt and sand)/ To separate insoluble solids from a solution (E.g. Sand from water)
22. Filtration 1. Glass rod 2. Retort stand 3. Mixture 4. Filter paper 5. Filter funnel 6. Beaker 7. Filtrate Filtration is usual method of separating solid from a liquid. Solid-Solid mixture Solid-Liquid mixture
36. Crystallisation Aim: To obtain PURE solids from a solution (solid will decompose upon strong heating). E.g. To obtain sugar from sugar solution , Copper (II) Sulphate from Copper (II) Sulphate solution . Do you know others? Solid-Liquid mixture solution
40. Have you noticed the difference of evaporation from Crystallisation? In a Solid-Liquid mixture , both Evaporation and Crystallisation is used to obtained solid from its solution. Most All How much solvent have to be vaporised? Yes No Does solid decompose upon strong heating? Crystallisation Evaporation
41. Summary: Evaporation & Crystallization To obtain a soluble solid from a liquid in solid-liquid mixture Evaporation Crystallization If solid does not decompose on heating If solid decomposes on heating
44. Questions 4. Which of the following is the correct order for purifying potassium nitrate from impure saltpetre (naturally occuring potassium nitrate) using water as a solvent? A) dissolve – filter – evaporate -crystallise B) dissolve – evaporate – crystallise - filter C) filter – dissolve – evaporate - crystallise D) evaporate – crystallise – dissolve - filter