A mixture consists of two or more different substances that are mixed but not chemically combined.
Why separate mixtures? 3 Many mixtures contain useful substances that we want to single out. Some common mixtures: air sea water freshwater in reservoirs crude oil
Separation Methods: 4 Magnetic attraction Filtration Evaporation Distillation Paper chromatography Physical methods
Separation Methods: 5 Physical methods Chemical methods vs New substance(s) formed.
Changes inchemical nature
Using chemical properties
No new substance formed.
No change in chemical nature
Using physical properties
1. Magnetic Attraction 6 separate magneticmaterials from non-magnetic materials (those that are not attracted by magnets)
Some alloys of rare earth metals
1. Magnetic Attraction 7 Fun stuff! Research online for “ferrofluid” and find out how it works!
1. Magnetic Attraction 8 Uses: Scrapyards use strong electromagnets to salvage scrap iron and steel from other junk materials separating magnetic ores from non-magnetic ones in mining food processing
1. Magnetic Attraction 9 Let’s see a magnetic crane in action!
Different filters.. 11
Different filters.. 12 Similarity between the filters?
What is Filtration then? 14 Used to separate an insolublesolid from a liquid in a solid-liquid mixture. residue filtrate
Other forms of filtration 15
More on kidney and ultrafiltration 17
Kangaroo rats have powerful kidneys! 18
Other examples 19 Baleen whale and its baleen plates
Other examples 20
Inner surface of beak has rows of keratinous plates (lamellae), covered with tiny hairs (cilia) through which food is strained out of water. 21
Uses of Evaporation 23 To obtain salt from sea water
24 Devil’s Golf Course, Death Valley National Park, California. Evaporated salt has formed into gnarled, complex crystalline shapes in on the salt pan, one of the largest in the world. The shapes are constantly evolving as occasional floods submerge the salt concretions before receding and depositing more salt.
Evaporation 25 Used to separate a dissolved solidfrom a liquid in a solid-liquid mixture. residue mixture
Distillation 26 Arnold Bochmove (1235 - 1310) gave recipes for liqueurs based on distilling wine with spices and herbs. Distillation of wine to produce gin and liqueurs became known in Paris by 1332 and spread throughout Europe.
Laboratory setup 27
Laboratory setup 28
Distillation 29 A process where a pure liquid is separated from a solid-liquid or liquid-liquid mixture. mixture distillate
Industrial distillation plants 30
Uses of Distillation 31 To make perfumes Desalination plant
What is this? 32 Oil refinery on Jurong Island
Fractional Distillation 33
A process where more than two liquids can be separated from a mixture of miscible liquids.
Oil refineries use fractional distillation to separate crude oil into useful product such as petrol, diesel and kerosene
How can we help? Ahmad the fisherman wishes to use salt to make some salted fish. But he has run out of salt supply! He knows that seawater contains salt. How can we help him obtain pure salt from seawater containing sand and pebbles? Dried Salted Fish
How can we help?? How can Ahmad get pure water from the seawater? Ahmad spotted some shimmering specks in the sand mixture which he thinks is iron metal. How can Ahmad get the iron? Ahmad accidentally spilled his bottle of wine(alcohol) into a pail of seawater. How can he obtain the wine again?
Paper Chromatography 40 Used to separate small amounts of mixtures Makes use of the fact that different substances dissolve to different extent in a solvent move at different rates through any particular solvent/medium.
Paper chromatography is used to identify the contents of a mixture or to test the purity of a liquid. 41 Different substances in the mixture are separated on the chromatography paper.
Uses of Paper Chromatography 42 Can be used to separate mixtures of coloured substances such as ink and dyes. e.g. dyes used in ink dyes used in food
Chromatography art! 43
Food for thought 44 How do you think forensic scientists make use of tiny amount of DNA available to make identifications? Hint: the method uses similar principle as paper chromatography. Do some research online!
Reverse osmosis 45
What is “osmosis”? 46 Move of water molecules across a partially permeable membrane from a region of high water potential (in other words, low solute concentration) to a region of low water potential (i.e. high solute concentration).
Partially permeable membrane 48 does not allow large molecules or ions through the pores but allows smaller components of the solution (such as the solvent) to pass freely.
Partially permeable membrane 49
Reverse osmosis 50
Reverse osmosis 51 a filtration method removes many types of large molecules and ions from solutions by applying high pressure to the solution when it is on one side of a partially permeable membrane. Solutes are retained on the pressurized side of the membrane and the pure solvent is allowed to pass to the other side.
Applications of Reverse Osmosis 52 Can be used for desalination Sea water is pre-treated to remove debris and contaminants pumped at high pressure through partially permeable membranes removes all traces of bacteria, viruses, chemicals and dissolved minerals
Reverse Osmosis 54 Singapore has a limited freshwater supply, so desalination of seawater is one good way to supplement freshwater supply.
Recap: desalination 55 What other separation method(s) you have learned can be used for desalination?