Cara untuk menjawab soalan 'definisi secara operasi'

2011-08-22T06:01:00.000-07:00

Assalamualaikum,

kepada rakan-rakan juga sesiapa yang masih tidak mengetahui cara untuk menjawab
'definisi secara operasi' dalam kertas soalan sains kertas 2.
terdapat 1 cara mudah untuk menjawab soalan tersebut.

caranya ialah:

1. salin semula soalan
2. tambahkan responding variable (rv)

contoh:

definisikan secara operasi 'kadar transpirasi'

mv: kelajuan kipas
rv : kedudukan gelembung angin

(soalan) + (rv)

definisi secara operasi 'kadar transpirasi' ialah kedudukan gelembung angin

Halogen Reactions

2011-08-17T06:35:00.000-07:00

Reactions of chlorine

2011-08-17T06:11:00.000-07:00

Reactions in Equilibrium

2011-08-17T06:03:00.000-07:00

Solubility

2011-08-17T05:49:00.000-07:00

REACTION BETWEEN METALS AND NON METALS

2011-08-16T07:00:00.000-07:00

PROPERTIES OF METALS

Metals are elements that have atoms arranged in rows. The electrons are easily released from metal atoms so that layers of metal atoms exist in a 'sea' of electrons.

Examples of Metals are gold, copper, lead, zinc, iron, magnesium, sodium, calcium and mercury.

Physical Properties of Metals include shiny lustre, greyish - silver colour, hardness, good heat and electricity conductivity, high melting and boiling points, malleability (can be hammered into a sheet) and ductility (can be pulled into a wire).

Some exceptions to these are the metals - sodium and calcium (very soft), gold and copper (yellowish colour), and mercury (low melting and boiling points).

Chemical Properties of Metals

Some metals are more reactive than others. This is because very reactive metals lose electrons easily. Metals such as sodium are very reactive and are explosive in air. Metals such as gold are very unreactive, and therefore do not corrode or tarnish in air.

CHEMICAL REACTIONS OF METALS

3 Chemical Reactions of Metals

Metal + Acid Salt + Hydrogen
Metal + Oxygen Metal Oxide
Metal+Water Metal Hydroxide + Hydrogen

Activity Series of Metals lists metals from the most reactive (e.g. potassium and sodium) to the least reactive (e.g. gold).

Potassium - K	Most Reactive
Sodium - Na
Calcium - Ca
Magnesium - Mg
Aluminium - Al

Zinc - Zn
Iron - Fe
Tin - Sn
Lead - Pb
	Least Reactive
Copper - Cu
Silver - Ag
Gold - Au

Corrosion is the process that occurs when a metal reacts with air, water or other substances in its surroundings.

Examples of Corrosion include the rusting of iron in oxygen to form iron oxide, and the green tarnish on copper.

4 Ways to Prevent Corrosion:

Painting - to prevent contact between the metal and oxygen
Coating with Plastic, Oil, Grease or Tar - to prevent oxygen contact with the metal
Coating with Metal - Galvanising iron with zinc
Sacrificial Protection - enclosing a metal to be protected with a more reactive metal which will corrode first

ALLOYS

Alloys are mixtures of metals with either other metals or with non-metals such as carbon and silicon. This is done to develop lighter, stronger or corrosion-resistant metal alloys.

NAME OF ALLOY	PERCENTAGE OF EACH METAL
Bronze	Copper (92%), tin (6%), zinc (2%)
Brass	Copper (70%), zinc (30%)
Steel	Iron (99%), carbon (1%)
Stainless steel	Iron (75%), carbon (1%), chromium (20%), nickel (5%)
Duralium	Aluminium (95%), copper (4%), manganese (1%)
Magnalium	Aluminium (70%), magnesium (30%)
Type metal	Lead (72%), antimony (18%), tin (10%)
Solder	Lead (50%), tin (50%)
Pewter	Tin (85%), copper (7%), bismuth (6%), antimony (2%)
Sterling silver	Silver (92.5%), copper (7.5%)
22 carat gold	Gold (92%), silver (4.9%), copper (3.1%)
18 carat gold	Gold (75%), silver (15%), copper (10%)

MINING AND MINERALS

3 Methods of Mining:

Open - Cut Mining involves digging a huge hole in the ground (e.g. iron, copper, uranium)
Shaft Mining involves mining in tunnels (e.g. coal, gemstones)
Dredging involves mixing large amounts of water with the crushed ore to allow the heavier minerals to settle to the bottom (e.g. tin, mineral sands)

Some Important Mining Terms:

Metal - the element within a mineral (e.g. iron)
Mineral - the compound of a metal in combination with other elements such as oxygen (e.g. haematite FeO)
Ore - a large deposit of a mineral which is economically viable to mine and refine (e.g. iron ore or haematite)
Gangue - the waste material of an ore from the crushing process

Some Common Metals and their Minerals:

Aluminium - Bauxite
Copper - Chalcopyrite
Iron - Haematite
Lead - Galena
Tin - Cassiterite
Titanium - Rutile and Ilmenite
Zinc - Sphalerite

REFINING METALS

After the ore has been mined, the metal has to be extracted or refined from the mineral. There are 2 main refining processes - smelting and electrolysis.

Smelting in a Blast Furnace

Smelting - Example 1

In the smelting process to extract lead from its mineral ore (Galena PbS), the galena is first roasted or reacted with oxygen to remove the sulphur.
Lead Sulphide (Galena) + Oxygen Lead Oxide + Sulphur Dioxide
PbS + O₂ PbO + SO₂
Then the lead oxide is reacted with the carbon in coke to obtain the refined lead.
Lead Oxide + Carbon Lead + Carbon Dioxide
PbO + C Pb + CO₂

Smelting - Example 2

In the smelting process to extract iron from its mineral ore (Haematite Fe O), the iron ore undergoes a series of reactions in the blast furnace. Again, carbon is in the form of coke. Also, limestone is added to remove the slag.
Heat comes from hot air forced into the furnace. The molten iron collects at the bottom of the furnace where it is tapped off.
Carbon + Oxygen Carbon Monoxide
C + O₂ CO
Iron Oxide + Carbon Monoxide Iron + Carbon Dioxide
FeO + CO Fe + CO₂

Electrolysis

₂

₃

Reaction of metal with non-metal

2011-08-16T06:57:00.000-07:00

LAND AND ITS RESOUCES

2011-08-16T06:47:00.000-07:00

MINERALS FOUND IN THE EARTH'S CRUST
1. Minerals are natural element or compound present in the Earth's crust.
2. minerals exist as natural element include
a) gold
b) silver
c) platinum
d) antimony
e) arsenic
f) iron (from meteorites)
g) copper
h) mercury (can be found in thermometer)
3. these free element are found in nature because they are inactive and does not combine with other elements.
4. minerals which exist as naturals compound include the examples given below

MINERALS	MAIN COMPOUND	CONSTITUENT ELEMENT
Haematite	Iron Oxide	Iron & Oxygen
Galena	Lead Sulphide	Lead & Sulphur
Calcite	Calcium Carbonate	Calcium, Carbon & Oxygen
Cassiterite	Tin Oxide	Tin & Oxygen
Malachite	Copper Carbonate	Copper, Carbon & Oxygen
Iron Pyrite	Iron Sulphide	Iron & Sulphur
Silica	Silicon Dioxide	Silicon & Oxygen

PHYSICAL PROPERTIES OF MINERALS

mohs' scale is a useful test for hardness of minerals.
for each number of hardness in the scale one minerals is used as a standard.

Table below show the hardness of minerals.

3. all minerals found in the earth's crust are not soluble in water. they have remained in the earth's crust for more than 2000 million years

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