Land n Its Resources

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FORM THREE SCIENCE

CHAPTER SIX

LAND AND ITSRESOURCES


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6.1 Minerals in the Earths crust

1. Minerals are natural elements (?) or compoundsthat exit in Earths crust.

2. Every mineral has a definite chemical composition and a crystalline structure.3. Naturally exist elementsstable (not reactive)- do not combine with other elements.- gold, silver, platinum, mercury.

4. Those cannot exist in element arenot stable (reactive)

- must form compound with other elements.- examples: Sodium chloride, water.

5. Most minerals found on the Earth are compounds of metals and non-metals.6. They exist in oxides (oxygen), sulphides (sulphur) or carbonates.

7. Examples:Bauxite Aluminium oxide Galena Lead sulphideHematite Iron oxide Limestone Calcium carbonateZinc blende Zinc sulphide Quartz Silicon dioxide


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Calcium oxide

Sodium silicate

Iron oxide Limestone Calcium carbonate


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Properties of minerals


Identification of minerals properties- hardness- solubility in water- effect of heat

Hardness

1. Hardness refers to a minerals resistance to scratches.2. When a mineral can scratch another one, it said to be harder. If in

turn it is scratched by another mineral, then it is said to be softer.3. Example: A scratches with B and there are scratches on B, so A is

harder.4. Hardness is measured in Mohs, the bigger the harder.5. Diamond is the hardest mineral.


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Solubility in water.

1. Most minerals cannot dissolve in water.2. Potassium and sodium compounds dissolve easily.

Effects of heating

1. Some compounds decompose when heated.2. Most oxides are stable and will not decompose when heated.3. Sulphides will decompose into oxide when heated:

Iron sulphide Iron oxide + Sulphur dioxide

4. Carbonate will decompose into oxide when heated.

Calcium carbonate Calcium oxide Carbon dioxide+


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6.2 Reactions between metals and non-metals

Reaction between metal and oxygen

1. When a metal is heated in the air, oxide is produced.2. A unstable metal reacts vigorously (strongly) when heated while a stable

one will react slowly (or never at all).


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Potassium permanganate

Releases oxygen when heated

Wire gause

Zinc powder

Zinc Zinc oxide

Metal Burning

Magnesium Burnsvigorously

Aluminium Burns brightly

Zinc Burns brightly

Iron GlowsCopper Glows slowly

Reactivity

Burning Reactivity

Burns

vigorously

Very reactive

Burnsbrightly

Reactive

Glows Less reactive

Glows slowly Not reactive


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Reaction between metal and sulphur

6.2 Reactions between metals and non-metals

1. When a metal is heated with sulphur, sulphide is produced.2. A unstable metal reacts vigorously (strongly) when heated while a stable

one will react slowly (or never at all).

Mixture of ironand sulphur powder

Iron Iron sulphide


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The effects of heating on oxides, sulphides and carbonates.

1. Heating does not affect most of the metal oxides.

2. Metal sulphides will decompose into oxide, release a gas,sulphur dioxide.

3. The sulphur dioxide is tested using acidified potassiummanganese solution, which will turn from purple to colourless (orthe purple colour solution is decolourised).

Ironsulphide

Potassium permanganate solution

Iron sulphide Iron oxide + Sulphur dioxide


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4. When carbonate is heated strongly, it becomes oxide and carbondioxide gas is released.

5. Carbon dioxide gas is tested using lime water.

Calciumcarbonate.

Lime water

Calcium carbonate Calcium oxide Carbon dioxide+


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6.3 Silicon compounds

1. Silicon is the second most abundant elementsin the Earth crust.

2. Silica and silicates are formed when siliconcombines with other elements.

Silica

1. Silica is formed when silicon combines with oxygen.2. It is also known as silicon dioxide.3. Examples: sand, quartz, gemstones like jasper.


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Silicate

1. Silicates are compounds silicon + oxygen + metal(or silica + metal).

2. Examples: clay, asbestos, mica, feldspar, topaz, rubiesand jade.

Topaz

Clay

Mica

Jade


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Silica and silicates are very stable, because:1. they are not soluble in water, except sodium silicate.2. they do not react with dilute acid.3. they are not affected by strong heating.

Due to the above properties silicon compounds are

very stable and widely found in the earths crust.


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Silicon compounds and their daily uses

Silica/cates uses

Sand Glass, concrete, mortar

Clay Brick. Tiles, roof tiles, pots, bowls, plates

Sodium silicate Preserving eggs, silica gel, furniture polish

Quartz Glass, ceramic

Mica Electrical insulator

Feldspar Ceramic, enamel, cement, brake pads

Asbestos Heat/fire/electric insulator, brake pads

Talcum Powder, lubricant

Topaz Jewel, decorative items

Silicon Silicon chips, transistors, fibre optic cable


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6.4 Calcium Compounds

1. Calcium reacts with carbon an oxygen to form calcium carbonate.2. Calcium exists naturally as chalk, marble, limestone, animal shells, teeth

and bones.

3. Properties of calcium carbonate:a. It is not soluble in water

b. It reacts with dilute acid to release carbon dioxide, leavingsalt and water.

Calcium carbonate + hydrochloric acid calcium chloride + carbon dioxide + water

c. It changes into calcium oxide and releases carbon dioxide when heatedstrongly.

Calcium carbonate (heated) calcium oxide + carbon dioxide


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Some chemical changes of calcium carbonate

Calcium carbonate (limestone)

Calcium oxide (quicklime)

Calcium hydroxide (Slaked lime) (S)

Calcium hydroxide (Lime water) (L)

Strong heating

Add a little water

Add more water


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Uses of calcium compounds and some of their properties.

Calcium carbonate

1. Limestone insoluble and hard, suitable for making cement,building and roads.

2. Used to remove impurities from the molten metal in tin and ironindustries.

3. Used to produce quicklime.

4. When form marble, used as floor slabs and table.

Calcium oxide

1. Quicklime forms alkali solution when added to water, used to

neutralize acidic soil.2. As dehydrating agent in manufacturing of ammonia gas.3. Used to produce slaked lime.


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Calcium hydroxide

1. Slaked lime dissolves in water and forms alkali solution, used toneutralize acidic soil

2. Used to make mortar for buildings.3. Used to make concrete plaster and chalk paints.4. Used to make limewater.


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6.5 Natural fuel resources and their importance. Click me first

1. It was a long way back when human knew how to make use of fuel to

power machineries to help ease their work.2. What is fuel then ?

3. Fuel is a substance that powers a great variety of machineries andimprove their output power.

4. There are many sources of fuel, like timber, petroleum, natural gas,etc.

5. Petroleum, natural gas and coal are naturally formed fuel.

Petroleum and natural gas

1. Millions of years ago, dead plankton, dead animals andplants are decomposed y bacteria.

2. t is later covered b sediment in the sea / river.3. Because of many layers of soil on top, the organic matter

is subjected to high pressure and high temperature.


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4. The high pressure and temperature cause chemicalreaction to take place and petroleum and natural gas isformed.

5. Under the ground, petroleum and natural gas is trappedbetween layers of impermeable rocks. Petroleum floats onwater and natural gas floats on petroleum.


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Coal

1. Dead plants, ferns, etc in swampy land millions of years ago form athick layer of decaying matter, called peat.

2. When covered with soil, under high pressure and high temperature,chemical reaction causes peat to form coal.


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Wood and charcoal

1. Woody plants have wood in their stems and branches. When dry, thesewood become a good source of cheap fuel.

2. When burnt, wood produces heat.3. When processed, wood becomes charcoal.4. When burnt, charcoal produces heat, with less soot.


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Fractional distillation of petroleum

1. When taken from the ground, petroleum is a dark,thick, sticky and smelly liquid which is neversuitable for burning.

2. When burns, petroleum will give out thick smoke, alot of soot with very little heat.


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3. In petroleum, there are many components, made up ofhydrocarbons.

4. Because each hydrocarbon has its own property, so it has its ownboiling point (also condensation point).

5. Example, petrol boils at 70oC, so at the same temperature, itcondenses.

6. The process that separates components in petroleum is known asfractional distillation.


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Fractional Distillation of Petroleum

1. First petroleum is heated tobecome vapour.

2. The vapour is channeled toa tower (distillation tower)where it is cooled incolumns of different

temperature3. At the appropriate column,vapour condenses andforms its liquid form ofpetroleum fraction

4. The lighter fraction

(petroleum gas) willcondense at the top of thetower. This is followed by theheavier ones and continueuntil the heaviest one at thebottom.

Petroleumgas

Petrol

Naphtha

Kerosene

Lubricatingoil

Diesel

Engine oil

Tar


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Fraction Temperature Uses

Petroleum

gas

< 25oC Bottled for cooking, chemicals and plastic

Petrol 40 - 75 oC Motor vehicles

Naphtha 75 - 150 oC Petrol-chemicals, fuel for planes

Kerosene 150 - 230 oC Fuel for planes, lamps, stoves, detergent

Diesel 220 - 250 oC Motor vehicles, machines

Engine oil >350 oC Ships

Bitumen >350 oC Surface roads, coating of pipes


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The contribution of the petroleum and natural gas industries to theeconomic development of our country

1. Export income and employment to the country.

2. Development of towns.3. Fertilizer projects.4. Transportation, mining, manufacturing, agriculture and

constructioncountrys progress.

Efficient ways of using natural fuel resources

1. Petroleum is a natural resource, will be depleted and finish one day.2. Conservation is the best method.3. Use of high technology to cut down on energy losses during energy

generation, energy transmission, and distribution of energy.- Use of energy efficient vehicles- Use of more public transport- Cut down of wastage of daily energy usage- Look for alternative sources of energy

- Cooperation from all the people.


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Conserve before its too late.

End ofChapter 6

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Land n Its Resources