CHAPTER 6LAND AND ITS RESOURCES6.1MINERAL IN EARTHS CRUST

Earth crust contains vast mineral resources.Minerals elements or compounds which occur naturally in earths crust.Galena (Lead sulphide)Quartz (Silicon dioxide)

Calcite (Calcium carbonate)

Pyrite (Iron sulphide)Kaolin (Aluminium silicate)

Minerals that can be found as natural elements:GoldSilverDiamonds Silver in its natural state

Diamond stonebefore being processedGold in natural state

Natural compounds formed when elements combines chemically.Example:

Other natural compoundsOxidesCarbonateSulphidesSilicates Copper + Carbon + Oxygen Copper carbonate

Elements that exist in some natural compounds

Copper carbonateIron oxide(Haematite)Lead sulphideCalcium silicates

Elements in Natural compoundsWhen oxygen combines with metal, oxides are formed.

Example:Metal + Oxygen Metal oxidesMagnesium + Oxygen Magnesium oxideIron + Oxygen iron oxide

Magnesium oxide

Carbonates contains carbon, oxygen and a metals.

Example:Metal + Oxygen + Carbon Metal carbonateCopper + Oxygen + Carbon Copper carbonateCalcium + Oxygen + Carbon Calcium carbonate

When metal combines with sulphur, sulphides are formed.

Example:Metal + sulphur Metal sulphideMagnesium + Sulphur Magnesium sulphideIron + Sulphur Iron sulphideZinc + Sulphur Zinc sulphide

When metal combines with silicon and oxygen chemically, silicates are formed.

Example:Metal + Silicon + Oxygen Metal silicatesCalcium + Silicon + Oxygen Calcium silicatesSodium + Silicon + Oxygen Sodium silicates

Sodium silicateSodium silicate

Summary Metal + Oxygen Metal oxidesMetal + Carbon + Oxygen Metal carbonateMetal + sulphur Metal sulphideMetal + Silicon + Oxygen Metal silicatesOxidesCarbonateSulphideSilicates

Properties of mineralsHardness of mineralsThe ability of minerals to resist being scratched.Soft minerals can be scratched easily.Diamond is an example of the hardest minerals.

Diamond is the hardest mineralfound on planet earth.Some metal such as sodiumare soft and can be cut easily.

Solubility of minerals in water Minerals that exist in the earths crust as natural elements and are non-reactive.Most of them do not dissolved in water.

Effects of heat on mineralsOxides such as gold and silver oxide will decompose to pure metals and oxygen when heated.

Oxygen gas can be detected by using glowing wooden splinter which will rekindles.

Carbonate compounds are not stable.When heated, it will decomposed into metal oxides and carbon dioxide.

Carbon dioxide gas can be detected by using lime water which will turns cloudy.

Most sulphide compounds are not stable and will be decomposed by heat into metal oxides and sulphur dioxide.

The presence of sulphur dioxide gas can be detected by using acidified potassium manganate (VII) solution.Magnesium ---- magnesium + sulphur sulphide oxide dioxideHeat

Reactions between metals and sulphurMetals react with sulphur to form metal sulphide.ExamplesMagnesium + Sulphur ---- magnesium Heat sulphideAluminium + Sulphur ---- Aluminium Heat sulphide

Experiment to observe the reaction between metals and sulphur

QuizWrite the word of equation for each reaction and state the end product.Heating of lead oxideHeating of calcium carbonateHeating of iron sulphideHeating of magnesiumHeating of calcium and sulphur powderHeating of sodium and silicon