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

5. 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

6. d)Compare and contrast the cleansing action of soap and detergents
Property
Soap
Detergent 1
sources 2
Molecular structure 3
Effectiveness in hard water 4
Effectiveness in acidic water 5
Cleaning power 6
Effect to the environment
Made from plant or animal
Made from petroleum fractions
R – COO – Na +
Where R is alkyl group
R SO4 – or
Forms scum with hard water
Does not form scum with hard water
Forms precipitate with acidic water
Does not form precipitate with acidic water
Less powerful
More powerful
Biodegradable and do not cause any pollution
Some detergents are non biodegradable and kill aquatic lives

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

8. 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

9. b) Oxygen is the oxidizing agent and Iron is the reducing agent
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

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

11. 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

12. Revision
on Rusting
of iron

13. POTASSIUM HEXACYANOFERATE(III) SOLUTION)?
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

14. To protect iron from rusting
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  Mg e
To protect iron from rusting

15. Presence of Fe 2+ ion iron Fe  Fe 2+ + 2e To encourage
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 e
To encourage
rusting of iron

16. Metals which are above iron in ECS inhibit iron from rusting
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

17. Ways to prevent RUSTINg of iron
Alloying
In stainless steel Iron is alloyed with carbon, chromium and nickel
Chromium and nickel forms a layer that does not rust
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

18. Explain the difference

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

20. 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  Mg e

21. 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 e

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

23. rubber molecules combine, coagulation occur
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

24. a) What is meant by vulcanization of rubber?
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 sulphur monochloride in methylbenzene as solvent

25. sulphur c) Describe how sulphur atoms change the properties of rubber
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

26. Similarities Differences
e) Compare and contrast the properties of vulcanized and unvulcanised rubber
Similarities
Both are ELASTIC Both do not CONDUCT HEAT AND ELECTRICITY
Differences
Differences
Vulcanised
Unvulcanised rubber
Elasticity
Hardness
Tensile strength
Resistance to heat
Effect of organic solvents
More elastic
LESS elastic
Harder
SOFTER
More tensile strength
LESS tensile strength
More resistance to heat
LESS resistance to heat
LESS SOLUBLE
MORE SOLUBLE

27. 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