Separation of substances: For class 6
- 1. CLASS-1 SEPARATION OF SUBSTANCES Dr. Madhava B Mallia Navi Mumbai Science Foundation Guidance session for Homi Bhabha Bal Vaidnyanik Competition 1
- 2. We are going to see… • Why we need to separate substances in a mixture • What are mixtures • Different type of mixtures • Methods of separation of mixtures 2
- 3. A look at our daily life… 3
- 4. Would you like to use these as such? 4
- 5. Noooooooooo………..Why? • Because it is IMPURE…. • So what is PURE? PURE means made up of only one type of matter or substance Impure Pure Impure Pure 5
- 6. Why substances become impure? • Because they mix with other substances Lets learn about mixtures…. • States of matter 1. Solid 2. Liquid 3. Gas 4. Plasma we will not consider it for the time being 6
- 7. Lets look at different ways of mixing… MIXTURES OF SOLID LARGER AMOUNT SMALLER AMOUNT Examples SOLID SOLID Stones in rice, Rice hulls in rice, fruit-salad SOLID LIQUID Mud, concrete SOLID GAS Hydrogen gas on palladium metal 7
- 8. MIXTURES OF LIQUID LARGER AMOUNT SMALLER AMOUNT Examples LIQUID SOLID Muddy water, mercury amalgum (metal dissolved in mecury) LIQUID LIQUID Vinegar (acetic acid in water) LIQUID GAS Air dissolved in water, Soda 8
- 9. MIXTURES OF GAS LARGER AMOUNT SMALLER AMOUNT Examples GAS SOLID Smoke, Dust Smoke – soot/carbon suspended in air Dust – fine sand particles suspended in air GAS LIQUID Water vapour GAS GAS Air 9
- 10. Types of mixtures • Homogeneous mixtures • Heterogeneous mixtures 10
- 11. Homogeneous mixtures A B C D 1. Take a glass of water 2. Add a spoon of salt 3. Mix it well 4. What is your observation? The salt dissolves completely What we get is a mixture? Yes, a liquid-solid mixture Now lets distribute this mixture into four small cups A, B, C & D Taste from each cup… Does it taste the same? Yes, This is because the salt we added was distributed uniformly in water A uniform mixture is called homogeneous mixture or SOLUTION
- 12. Examples of homogeneous mixtures or solutions • Alloys – Alloys are homogeneous mixture of two or more metals Brass – an alloy of copper and zin Bronze – an alloy of copper, tin and small amounts of other metals • Fruit juices without pulp • Sugar dissolved in water • Air – mixture of 78.09% nitrogen, 20.95% oxygen, 0.93% argon, 0.04% carbon dioxide, and small amounts of other gases. 12
- 13. Heterogeneous mixtures 13 A B C Will each plate A, B and C contain same amount of different fruits? No….different plates contain fruits in different amount A non-uniform mixture is called heterogeneous mixture
- 14. Non-mixing substances • Certain substances do not mix with each other – Oil and water – Wax and water 14
- 15. Would you like to use these as such? 15
- 16. Methods of separation • Hand picking • When will we use this method? – Impurity to be separated is larger in size – Impurity to be separated is smaller in quantity Example: Separation of stones, hull, other grains etc. from rice WILL YOU USE HAND PICKING IF RICE IS MIXED WITH SAND? 16
- 17. • Threshing • When will we use this method? – material to be separated is loosely bound – material to be separated is too larger in quantity for hand picking Examples: Separation of grains from stalk Removal of dirt from cloths 17 Methods of separation
- 18. • Winnowing • When will we use this method? – When the impurity to be separated is much lighter for the wind to carry it away Examples: Separation of husk from grains Separation of peanut peals 18 Methods of separation
- 19. • Sieving • When will we use this method? – Impurities are bigger in size than the material to be purified Examples: Separation of stones and insects from flour Separation of stones and pebbles from sand HAND PICKING IS POSSIBLE HERE, BUT IT WILL BE TIME CONSUMING 19 Methods of separation
- 20. • Sedimentation followed by decantation • When will we use this method? – Separation of heavier impurities in liquids – Separation of lighter impurities in solids Examples: Separation of sand from water Separation of husk from rice 20 Methods of separation
- 21. 21 Decantation
- 22. • Filtration • When will we use this method? – When decantation is not satisfactory!! Examples: Separation of tea leaves from tea Separation of home-made paneer 22 Methods of separation
- 23. • Evaporation • Evaporation is the process by which water changes from liquid state to vapor. 23 Methods of separation
- 24. • When will we use this method? – When we have to recover substances dissolved in water 24 Evaporation SALT Salt farm or salt pan
- 25. How will you separate salt mixed with sand? (Using combination of methods) 25 SALT SAND • Dissolve salt + sand mixture in water Salt will dissolve in water • Allow the mixture to stand for some time Sand will settle down (sedimentation) • Separate sand from salt water (decantation or filtration) • Evaporate salt water to recover salt (Evaporation) WHAT IF WE WANT TO COLLECT WATER ALSO?
- 26. Condensation • Condensation is the process of conversion of vapors into liquid 26 Water evaporating to Atmosphere Salt water So we have to cool the vapors to condense it How to recover evaporating water?
- 27. 27 Water evaporating to Atmosphere Natural evaporation is very slow VERY DIFFICULT TO CONDENCE VAPOURS ice
- 28. • Magnetic separation • When will we use this method? – Either substance to be purified or the impurity is magnetic Example: Separation of iron filings from sand 28 Methods of separation
- 29. Separation of a mixture of salt, sand and iron filings • Step 1: Separate iron filings using a magnet • Step 2: Add the remaining mixture to water • Step 3: Decant/filter off sand • Step 4: Evaporate the solution to recover salt 29
- 30. Industrial methods of separation • Industrial scale large scale • Methods – Centrifugation – Distillation – Magnetic separation 30
- 31. • Centrifugation It is a technique that uses centrifugal force to separate substances Example: Quick separation of sand and water (muddy water) Separation of red bloods cells, white blood cells etc. from blood 31 Industrial methods of separation
- 32. 32 Centripetal force Towards the centre Centrifugal force Away from the centre If the string breaks…..the stone will move away from the centre
- 33. 33 Centrifugal force on mud/sand particles Blood before and after centrifugation There is a centrifuge in most of your homes – can you identify?
- 35. • Distillation • Method used to separate two liquids which boil at different temperatures Example: Distillation of salt water to obtain pure water Distillation of ethanol from water 35 Industrial methods of separation Substance Boiling point Salt Very very high Ethanol 78.3 degree centigrade Water 100 C
- 37. • Petroleum products from crude oil – Petrol, diesel, aviation turbine oil, tar… 37
- 38. • Magnetic separation • When will we use this method? – When material to be separated or the impurity is magnetic Example: Separation of metals in recycling centers Separation of ore from sand and other impurities 38 Industrial methods of separation
- 39. Iron ore separator 39 Iron ore Feeder
- 40. Properties of material Vs Method of separation 40 Size/Shape Weakly bound substances/impurities Weight (light/heavy) Density (mass per unit volume) Volatility (tendency to evaporate under normal conditions) Magnetic property Hand picking Threshing Winnowing Sieving Sedimentation Decantation Filtration Evaporation Condensation Centrifugation Distillation Magnetic separation
- 41. Separation based on shape 41
- 42. Saturated solution • A solution in which we cannot dissolve a substance any further is called a saturated solution 42 Unsaturated solution Unsaturated solution saturated solution
- 43. 43 Substance Solubility in 500 mL of water at 25 degree centigrade Baking soda (Sodium bicarbonate) 48 gram Table salt 180 gram Sugar 1000 gram