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Revision on soap and detergent

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  1. Revision on soap and detergent Structure Cleansing action Compare soap and detergent

  2. STRUCTURE of SOAP PARTICLE STRUCTURE OF DETERGENT PARTICLE • the tail part • the head part • the organic part • the ionic part • the hydrophilic part • the hydrophobic part

  3. cleansing action of soap or detergent. a) State three abilities of both soap and detergent that enable them to act as cleansing agents i.Ability to lower the surface tension of water This helps to wet the cloth better ii. To emulsify oil or grease, (break the oil or grease into smaller droplets) iii. Suspend oil or grease in water, Prevent the oil or grease from redeposit on the surface of the cloth

  4. Describe the cleansing action of soap and detergent • 1) Soap dissolves in water and lowers the surface tension of water. This helps to wet the cloth better • 2) The hydrophobic part ( tail part) dissolves In grease , the hydrophilic part ( head part) dissolves in water 3) Movement of water during scrubbing helps to loosen the grease and lift the grease off the surface • 4) Repulsion of negative charges break the grease into small droplets. Rinsing washes away these droplets and leaves the cloth clean

  5. d)Compare and contrast the cleansing action of soap and detergents

  6. Explain the difference soap detergent Hard water contains Mg 2+ ions and Ca2+ ions • Detergent form soluble salt with Mg 2+ ions and Ca2+ • No scum is formed, • so detergent can function as cleaning agent • But soap form insoluble salt with Mg 2+ ions and Ca2+ • Scum is formed , • so soap cannot function as cleaning agent

  7. Revision on rusting of iron Conditions for rusting Describe process of rusting Effect of other metals on rusting of iron Ways to prevent rusting of iron

  8. Presence of water and oxygen State conditions of rusting b) State the function of oxygen and iron in the rusting of iron b) Oxygen is the oxidizing agent and Iron is the reducing agent

  9. DESCRIBE PROCESS OF RUSTING IN TERMS OF OXIDATION AND REDUCTION REACTION e Fe 2+ cathode cathode anode

  10. Step 1- At anode, iron atom is oxidized to form iron(II) ions Step 2- Electron flow through metal to cathode where there are plenty of dissolved oxygen - Electron are gained by Oxygen to form hydroxide ions Step 3- iron (II) ions combined with hydroxide ions to form iron(II) hydroxide Step 4- the iron(II) hydroxide rapidly oxidesed by oxygen to form RUST

  11. Revision on Rusting of iron

  12. Revision on Rusting of iron • WHAT IS THE FUNCTION OF • POTASSIUM HEXACYANOFERATE(III) SOLUTION)? • B) PHENOLPHTHALEIN? • C) AGAR? TO DETECT THE PRESENCE OF IRON(II) ION TO DETECT THE PRESENCE OF HYDROXIDE ION TO TRAP THE COLOUR FORMED DURING REACTION

  13. WHY DOES THE PHENOLPHTAHLEIN CHANGE TO PINK IN IRON NAIL WITH MAGNESIUM? • WHICH METAL UNDERGO CORROSION? • WRITE HALF EQUATION FOR THIS REACTION • WHAT IS THE ROLE OF MAGNESIUM IN THIS EXPERIMENT? Presence of OH- ion magnesium Mg  Mg2+ + 2e To protect iron from rusting

  14. Revision on Rusting of iron • WHY DOES THE POTASSIUM HEXACYANOFERRATE(III) CHANGE TO BLUE IN IRON NAIL WITH COPPER? • WHICH METAL UNDERGO CORROSION? • WRITE HALF EQUATION FOR THIS REACTION • WHAT IS THE ROLE OF COPPER IN THIS EXPERIMENT? Presence of Fe 2+ ion iron Fe  Fe 2+ + 2e To encourage rusting of iron

  15. Revision on Rusting of iron • WHAT IS THE ROLE OF METALS THAT ARE IN CONTACT with iron IN THE RUSTING OF IRON? Metals which are above iron in ECS inhibit iron from rusting Metals which are below iron in ECS encourage rusting of iron

  16. Ways to prevent RUSTINg of iron • In stainless steel Iron is alloyed with carbon, chromium and nickel • Chromium and nickel forms a layer that does not rust • Alloying • Sacrificial protection • Iron is connected to a more electropositive metal, example magnesium or zinc • Mg or Zinc will corrode first, so protect iron from rusting • iron or steel is coated with a thin layer of zinc • When scratched, zinc will corrode first because zinc is more electropositive than iron • Galvanising • Tin plating • sheets of steel are coated with a thin layer of tin • But if scratched, iron will rust, because tin is less electropositive than iron

  17. Explain the difference

  18. In test tube 1 Blue colour shows presence of Fe 2+ ions Iron nail rusts , due to presence of water and oxygen Fe  Fe 2+ + 2e

  19. In test tube 2 • High intensity of pink colour shows high conc of OH – ions • NO rusting of iron occur, Magneium undergo corrosion • Mg is more electropositive than iron, so protect iron from rusting Mg  Mg2+ + 2e

  20. In test tube 3 • High intensity of blue colour shows high conc of Fe 2+ ions • Iron nail rusts , • Copper is less electropositive than iron, so • Copper encourage rusting of iron Fe  Fe 2+ + 2e

  21. Revision of Rubber and coagulation of latex How coagulation of latex occur Vulcanisation of rubber

  22. HOW coagulation of latex occur LATEX BEFORE ACID IS ADDED Rubber molecules repel each other No coagulation occur ADD ACID, or bacteria acts on latex to produce lactic acid. (H + IONS) neutralize the negatively charged of rubber articles Rubber particles collide Rubber membranes rapture rubber molecules combine, coagulation occur

  23. VULCANISED RUBBER a) What is meant by vulcanization of rubber? ADDITION OF SULPHUR TO RUBBER AT 140 OC AND HIGH PRESSURE IN THE PRESENCE OF ZINC OXIDE AS THE CATALYST b) In industry, how does the vulcanization of rubber is carried out? By heating latex with SULPHUR or a solution of sulphurmonochloride in methylbenzene as solvent

  24. c) Describe how sulphur atoms change the properties of rubber sulphur cross-link • In vulcanization …………..atoms form …………………between rubber molecules • These …………………….prevent rubber……………………… from sliding too much when …………………………….The rubber molecules return to their ………………... position after being stretched. cross – LINK MOLECULES • STRETCHED ORIGINAL d) Draw cross-linkage of sulphur

  25. e) Compare and contrast the properties of vulcanized and unvulcanised rubber • Similarities Both are ELASTIC Both do not CONDUCT HEAT AND ELECTRICITY • Differences

  26. f) WHAT IS THE DIFFERENCE BETWEEN natural rubber over synthetic rubber in terms of source ? Natural rubber is made from latex of rubber tree Synthethic rubber is man-made rubber from chemical substance G) State one advantage of natural rubber over synthetic rubber Only natural rubber can absorb the high STRESS, STRENGH AND HEAT ………( in tyres) produced during landing and taking off of an aero plane