SCIENCE - FORM 3

LAND AND ITSRESOURCES

                                                   VARIOUS MINERALS IN THE EARTH CRUST

1.   Minerals form the Earth crust.

2.   Minerals are elements or chemical compounds that are naturally present in the Earth       crust.

3.   Each type of mineral has its own chemical content.

4.   Examples of common minerals are gold, silver, limestone and tin ore.

5.   Minerals exist in the form of element or compound.                                   

A.   Natural mineral elements

B.   Natural mineral compounds

1.   Most elements are active and tend to combine with other elements to form compounds.

2.   Minerals in the form of compounds consist of combinations of a few types of different       element. Some examples of natural mineral compounds are tin ore, clay and limestone.

3.   Most minerals in the Earth crust exist in the form of compounds especially oxide,       carbonate, sulphide and silicate.

A few types of natural mineral, mineral content and elements that form it

C.   Characteristics of minerals

1.   Most minerals are still in existence and have not changed in the Earth crust because       minerals are generally hard and do not dissolve in water.

2.   The characteristics of a mineral depends on the content and arrangement of atoms in it.

3.   Characteristics of minerals are divided into:      (a)   physical characteristics such as colour, hardness, luminosity and shape of crystals      (b)   chemical characteristics such as solubility in water, chemical reactions and effect of                 heat on it.

physical characteristics of mineral

1.   Minerals have different colours.

2.   Hardness of a mineral refers to its resistance against erosion and scratches.

3.   A hard mineral is able to scratch a mineral that is less hard.

4.   Generally, all metal oxides, sulphides and carbonates are hard minerals.

5.   Most minerals exist in the form of crystals. Each crystal has the same shape.

chemical characteristics of minerals

1.   Most minerals do not dissolve in water.

2.   Minerals like metal oxide and silicate normally do not decompose when heated.

3.   Some minerals like metal carbonates and sulphides can be easily decomposed by heating.       The effect of heat decomposes the compound into its elements or other compounds.       

4.   Effect of heat on metal carbonate

     (a)  Heat decomposes metal carbonate into metal oxide and releases carbon dioxide as            shown in the following equation.

     (b)   Example,       

     (c)   Carbon dioxide that is released can be tested by using lime water. Lime water will turn             cloudy in the presence of carbon dioxide.

5.   Effect of heat on metal sulphide          (a)   Nearly all metal sulphides decompose when heated to release sulphur dioxide and                   form metal oxide as in the following equation.

      (b)   Example,       

       (c)   Sulphur dioxide is an acidic gas that can be tested with                (i)   acidic potassium manganate (VII) solution. This gas bleaches the purple colour of                       the solution.               (ii)  acidic potassium dichromate (VI) solution. This gas changes the orange-coloured                     solution to green.

                                        (a)   hardness                                        (b)   solubility in water                                        (c)   effect of heat

                            Arrangement of apparatus to study characteristics of minerals

       1.   The hardness of minerals is tested by scratching each mineral with fingernails or a                    knife.The mineral is soft if it can be scratched with fingernails and it is hard if it can              only be scratched with a knife.

       2.   A little mineral powder is shaken in a test tube that is filled with water. Observations              are made on whether the mineral dissolves in water.

       3.   A little mineral powder is put into a test tube and heated. Any gas released is tested              with lime water and acidic potassium manganate(VII) solution as shown in figure              above.

       4.   Observations are recorded in the table provided.

       1.   Word equations that can represent the chemical reactions that happen when                              compounds are heated is as shown.

       2.   Mineral characteristics like hardness and insolubility in water makes it still present in              the Earth crust although this mineral has undergone weathering for millions of years.

       1.   Most minerals in the Earth crust are hard and do not dissolve in water.        2.   Most sulphides decompose by releasing sulphur dioxide when heated.       3.   Most carbonates decompose by releasing carbon dioxide when heated.

       1.   Apart from acidic potassium manganate(VII) solution, acidic potassium dichromate(VI)                solution can also be used to test the presence of sulphur dioxide. In the presence of                sulphur dioxide gas, potassium dichromate (VI) solution will change colour from              orange to green.

       2.   Copper carbonate changes colour from green to black when heated.

REACTION BETWEEN METALS AND NON-METALS

A.  Metals and Non-metals

1.   There are more than 100 elements in the Earth's crust.

2.   You have learnt about the properties of metals and non-metals in Form 1 (Chapter 4).

3.   Most metals and non-metals react to form compounds.

B.   Reactions of Metals with Oxygen

1.   Most metals do not exist as elements in the Earth's crust. They combine with oxygen to       form metal oxides.

2.   Examples of ores that exist as metal oxides in Earth's crust include:

      -   Bauxide (aluminium oxide)      -   Hematite (aluminium oxide)      -   Cassiterite (tin oxide)

3.   Most metals lose their lustre after some time because they react with the oxygen in the       air and form metal oxides. This process is called oxidation. For example,

Arrangement of apparatus to study the reaction between metal and oxygen              1.   A strip of magnesium about 5 cm long is clipped with a tongs.       2.   The magnesium strip is heated with flame from the Bunsen burner and the                                  observation obtained is recorded in a table.       3.   Arrangement of apparatus as shown in Figure above is prepared.

       4.   Metal filings in an asbestos cup (asbestos paper that is folded into cup-shape) is                      heated over a strong heat and followed by solid potassium manganate(VII).

       5.   Observation is recorded in the same table.

       1.   Solid potassium manganate(VII) is heated to supply oxygen that is needed for metal                  reaction.       2.   Glass wool prevents the solid potassium manganate(VII) from mixing with metal                          filings.       3.   Metal reacts with oxygen to form metal oxide.       4.   Different metals have different reactivity with oxygen.       5.   The chemical equations in word form that represent reactions between magnesium,                  aluminium, zinc and iron metals with oxygen are shown as follows.

            

       6.   The trend in reactivity between metals and oxygen in descending order is as follows.

Metal reacts with oxygen to form metal oxide.

When copper reacts with oxygen, it only embers a little in a slow rate to produce black powder, i.e. copper(II) oxide. This is because copper is a less reactive metal.

C.   Reaction of Metals with Sulphur

1.   The elements sulphur is found abundantly near volcanoes.

2.   Other than oxygen, sulphur can also react with metals.

3.   Sulphur is a reactive element. Like oxygen, it combines easily with metals to form metal           sulphides.

4.   A large number of ores in the Earth's crust are sulphur compounds. For example,

       1.   Mixture of magnesium filings and sulphur powder is heated in a test tube.

       2.   Observation obtained is recorded in a table.       3.   The activity is repeated using aluminium, zinc and iron filings.

       1.   Metals have different reactivity with sulphur.       2.   Metal reacts with sulphur to form metal sulphide.       3.   Chemical equations in word form that represent reations between magnesium,                          aluminium, zinc and iron with sulphur are as shown below.

                   4.   The trend in reactivity between metals and sulphur in descending order is as follows.

        Metal reacts with sulphur to form metal sulphide.

       Mixture of iron and sulphur produces embers when heated. Iron filings change colour to        black.

SILICON COMPOUNDS

1.   Silicon is the second most abundant non-metal element found in the Earth crust.

2.   Silicon is not found as a free element in nature.

3.   Silicon usually combines with other elements like metal and oxygen to form a       silicon compound.

4.   Silica and silicate are silicon compounds.

A.   Silica

1.   Silica is also known as silicon dioxide.2.   Silica consist of a combination of silicon and oxygen elements in the following       equation.

                                      3.   Example of silica are sand, quartz and flint.

B. Silicate

1.   Silicates are silicon compounds that contains silicon, oxygen elements and metals.      2.   Silicate is formed when silicon combines with oxygen and metal.

3.   Examples of silicates include clay, mica, feldspar and asbestos. Most ornamental       stones like jade, ruby and topaz are silicates.

C.  Characteristics of silicon compounds

1.   Both silicon compounds, i.e. silica and silicate, are very stable, i.e. not chemically       reactive.

2.   Silicon compounds:      (a)   do not dissolve in water      (b)   do not react with acid      (c)   do not decompose when heated

3.   These characteristics of silicon compounds result in their existence as the second most       abundant compound found in the Earth crust.

Studying the stability of silica and silicates

       1.   A little sand (silica) is shaken with 5 cm³ of water in a test tube and is observed to find              out if the sand dissolves in water.       2.   5 cm³ of dilute hydrochloric acid is added to a little sand in another test tube and the                observation is recorded.       3.   A little sand is heated in a test tube and is observed to find out if sand is decomposed              in heat.       4.   The activity is repeated using quartz(silica) and clay (silicate).       5.   All observations are recorded in a table.  

       1.   Silicon compounds are very stable, i.e. they do not dissolve in water, do not react with              acid and do not decompose in heat.       2.   Silica and silicate are two types of silicon compound.       3.   Sand and quartz are silica compounds while clay is a silicate compound.

       Silicon compounds:       (a)   do not dissolve in water       (b)   do not react with acid       (c)   do not decompose in heat

D.   Uses of silicon compounds in daily life     

1.   The stable characteristic of silicon compounds enable them to be used to make many       things.

2.   Things like glass, mortar, ceramic, tiles and so on are all made from silicon compounds.

3.   Pure silicon is used to make electronic chips. Such electronic chips are sometimes called       silicon chips.

4.   A tiny silicon chip contains many complicated electronic components and circuits. Such       electronic chips are used in eletronic equipment like computers, calculators and digital       clocks.

5.   Fibres made from silicon compounds are called optic fibres. Optic fibres are used to:      (a)   replace copper wire to send information like sound data, video and etc., at the speed              of light.      (b)  observe internal organs like the stomach without having to operate on the patient in                the medical field.

CALCIUM COMPOUNDS

1.   Calcium is a reactive element and is not found in a free form. Calcium is found as calcium      carbonate, a naturally occurring compound.

2.   Calcium carbonate consists of calcium, oxygen and carbon.

3.   Natural calcium carbonate exists in many forms. Some examples are calcite, chalk (not       blackboard chalk), marble, limestone, snimal shells, teeth and bones of animals.

                                       (a)                                                       (b)

 Arrangement of apparatus to study the characteristics of calcium carbonate

       1.   A few bits of marble are shaken with water in a test tube. The marble is observed to                  determine whether it dissolves in water.       2.   About 5 cm³ dilute hydrochloric acid is added to a test tube containing a few bits of                    marble.       3.   Whatever gas that is released is tested with limewater as shown in figure above (a)                  and the observation is recorded.       4.   A few bits or marble are heated over strong heat in a test tube and the gas released                is tested with limewater as shown in figure above (b).

       1.   Carbon dioxide is released when calcium carbonate reacts with acid and when marble              is heated.       2.   Equations representing the reaction of acid and the effect of heat on calcium                              carbonate are as follows.

                   3.   Limestone, corals, cockle shells, eggshells and snail shells are examples of materials              that can be used to replace marble.

       Calcium carbonate:

       (a)   does not dissolve in water       (b)   releases carbon dioxide when reacting with acid       (c)   releases carbon dioxide when heated over strong heat

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4.   The properties of calcium carbonate

      (a)   Calcium carbonate reacts with dilute acids to release carbon dioxide. Water and salt                (calcium chloride) are also formed. The word equation for this reaction is

      (b)   When heated strongly, calcium carbonate changes to calcium oxide (quicklime) and                   carbon dioxide is released.

      (c)   Calcium carbonate does not dissolve (insoluble) in water.

5.   Formation of calcium oxide and calcium hydroxide      (a)   Calcium carbonate changes to calcium oxide when heated strongly.      (b)   When a little water is added to calcium oxide, it turns into calcium hydroxide.      (c)   Calcium hydroxide(quicklime) dissolves in water to become a solution of limewater.

 

Arrangement of apparatus to study the formation of calcium oxide and calcium hydroxide

      1.   Nichrome wire that is about 25 cm long is cut.      2.   A thick piece of marble is tied to one end of the nichrome wire and hung on a glass                rod.

      3.   The thick marble piece is heated over strong heat for 5 minutes.      4.   The the heated marble piece is placed with its wire in a crucible. A few drops of water               is dripped on the marble with a glass tube. The observation obtained is recorded.       5.   Then, more water is dripped on the marble until it fills one third of the crucible.      6.   The solution formed in the crucible is poured into a test tube.      7.   Slowly, air (carbon dioxide) is blown through a glass tube into the solution. The                         observation obtained is recorded.

      1.   Calcium oxide is formed when calcium carbonate is heated over strong heat.

      2.   Solid calcium hydroxide is formed when water is dripped on quicklime.

      3.   Solid calcium hydroxide dissolves a little in water to form calcium hydroxide solution.

      1.   Heating calcium carbonate produces calcium oxide. Calcium oxide reacts with water to             produce solid calcium hydroxide.

      2.   Solid calcium hydroxide dissolves in water to produce calcium hydroxide solution.

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Summary

Formation of quicklime, slaked lime and lime water

A.   Uses of Calcium Compounds and Their Properties

1.   Calcium carbonate

      (a)   Calcium carbonates such as limestone can withstand the weathering porcess                             because this compound is hard and does not dissolve in water.      (b)   This is the reason for using limestone to make cement, buildings and roads.      (c)   Limestone is also used to remove impurities form molten metal in the tin and iron ore               industries.      (d)   Limestone is used to produce quicklime.      (e)   Marble that is hard and colourful is used as floor slabs and table tops. 

2.   Calcium oxide   

      (a)   Quicklime (calcium oxide) dissolves in water to form an alkali. This alkali is used to                     neutralise acidic soils.      (b)   Calcium oxide is used as a hydrating agent in preparing ammonia gas.      (c)   Calcium oxide is used to produce slaked lime and calcium carbide. Calcium carbide is               use to produce acetylene gas.  

3.   Calcium hydroxide

      (a)   Slaked lime (calcium hydroxide) dissolves in water and is alkaline. It is used to                           neutralise acidic soils.      (b)   Calcium hydroxide is used to make mortar for buildings.      (c)   Calcium hydroxide is used to make concrete plaster and chalk paint in the                                   construction industry.      (d)   Calcium hydroxide is used to make limewater which is used in laboratories.

NATURAL FUEL RESOURCES AND THEIR IMPORTANCE

1.   Natural fuel resources found in the Earth crust include:(a)   petroleum (crude oil)(b)   natural gas

(c)   coal(d)   wood

2.   Petroleum and natural gas are hydrocarbon compounds because both consist of a       compound mixture that is only formed from hydrogen and carbon elements.

3.   Petroleum, natural gas and coal are fossil fuels that are formed from te remains of living       things that were buried in layers of the Earth crust millions of years ago.

A.   Petroleum

1.   Petroleum is a black and viscous liquid.

2.   Petroleum is formed from decayed dead sea animals and plants that settled on the sea       bed millions of years ago.

3.   Sediments of these organisms changed into petroleum after being subjected to high       temperature and pressure for a long period of time.

4.   Petroleum in the Earth crust is normally trapped between two layers of impermeable                 rocks and is obtained together with natural gas.

Petroleum trapped between layers of rocks in the Earth crust

5.   Petroleum consists of a mixture of various hydrocarbon compounds.

6.   These various hydrocarbon compounds can be separated through fractional distillation.       This is because all the different types of hyrocarbon have different boiling points.

7.   Thus each type of hydrocarbon can be distilled out at its own distillation temperature.

8.   The higher the boiling point of a petroleum fraction:(a)   the darker is its colour(b)   the higher is its viscosity(c)   the more difficult it is to burn(d)   the more soot its flames produce

9.   All petroleum fractions do not dissolve in water.

Arrangement of apparatus to study the process of fractional distillation of petroleum

       1.   About 20 cm³ of crude petroleum is pured into a boiling tube together with a little              glass wool.       2.   Arrangement of apparatus as shown in figure above is set up.       3.   The petroleum in the boiling tube is heated slowly.

       4.   Three petroleum fractions that have been distilled out are collected at the following                 temperatures:             (a)   first fraction below 120 °C             (b)   second fraction between 120 °C and 170 °C             (c)   third fraction between 170 °C and 220 °C       5.   Characteristics of each of the following petroleum fractions are observed:             (a)   Colour                                     (b)   Viscosity             (c)   Colour of flame                      (d)   Flammability             (e)   Soot quantity

       1.   The function of glass wool is to break air bubbles fo that the petroleum does not              surge up and enter the delivery tube.       2.   Water in the beaker is used to condense vapour into liquid.       3.   The process of separating petroleum fractions in this activity is called fractional                        distillation.       4.   Different boiling points of each petroleum fractions enable the fractions to be                            separated.       5.   The higher the boiling point of a petroleum fraction:             (a)   the darker is its colour             (b)   the more viscous the fraction             (c)   the more difficult it is for the fraction to burn             (d)   the more soot its flame produces

       Petroleum fractions can be separated through the process of fractional distillation                    because each petroleum fraction has a different boiling point.

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10.  In industry, the filtering of crude petroleum through fractional distillation is done in a        petroleum distillation tower.  11.  Petroleum fractions that have different boiling points are distilled at different sections of        the tower.

12.  Light fractions with low boiling points condense in the upper sections of the tower while        heavy fractions with high boiling points condense at the base of the tower.

13.  Crude oil is heated until 400 °C to produce a mixture of vapour and liquid.

14.  This mixture is then channelled to the fractional distillation tower which is divided into        sections.

15.  When the mixture goes up the tower, the liquid will condense and fall to the bottom while

       vapour that is still hot rises to the top.

                                    Petroleum fractional                   Crude oil is stored in                                       distillation tower                              in big tanks

Temperature and products of petroleum distillation

Fractional distillation of crude oil

16.  Generally, the products of petroleum distillation are used:(a)   as energy resource or fuel(b)   to produce various synthetic substances including        (i)   synthetic fibres (rayon and nylon) used in making ropes        (ii)  polyvinyl chloride (PVC) used in making water pipes        (iii) polythene used in making plastic bottles        (vi) synthetic rubber used in making tyres

Petroleum fractions and their uses

B. Natural gas

1.   Natural gas is a hydrocarbon compound usually obtained together with petroleum.

2.   Natural gas is used:      (a)   as fuel in factories and in the home      (b)   to make ammonia and nitrogen-based fertiliser (urea fertiliser)

C.  Contributions of petroleum and natural gas industry       to the country

1.   Petroleum and natural gas are found in large quantities in the coastal regions of        Terengganu, Sabah and Sarawak.      

2.   Constributions of the petroleum and natural gas industry to the country include:(a)   about 75% of the total energy used in industries in Malaysia come from these two fuels.(b)   the expansion of various other industries like the petrochemistry industry(c)   providing job opportunities for the people like in the mining, filtering and the         manufacturing of petrochemical substances industry.(d)   the export of petroleum and natural gas brings in high revenue to the country.

Formation of coal

1.   Coal is formed from swamp plants that died millions of years ago and have been       compressed by layers of earth on top of it.

2.   High pressure and temperature that act on these plants change them into coal. The main       content of coal is carbon.

3.   Uses of coal include:(a)   generating electric energy in thermoelectric generating stations(b)   extracting metal from its ore by using coke in a blast furnace(c)   making chemical substances like dye and naphthalene (moth balls) from coal tar(d)   warming the house in winter

E.   Efficient ways of using natural fuel resources

1.   Fossil fuels like petroleum, natural gas and coal are energy resources that cannot be       renewed.

2.   These energy resources are most widely used throughout the world.

3.   These energy resources are limited and their supply will run out in the future.

4.   Therefore, these energy resources must be used wisely and economically to avoid       wastage of natural resources.

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