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| Properties, ores, Alloys of Metals. |
Properties of metals
Copper-ores and extraction of copper
Alloys of copper
Iron and its properties
Ores of iron and extraction of iron
Alloys.
Review
Elements are classified into metals and non-metals.
Metals are normal temperatures exist as solids, except mercury and gallium which are liquids.
Metals are good conductors of hear and electricity.Metals are normal temperatures exist as solids, except mercury and gallium which are liquids.
Generally metals are malleable, ductile and hard.
Metals have a tendency to donate electrons and hence they are electro positive.
Metals displace hydrogen gas from dilute acids.
INTRODUCTION
Properties of metals are different from that of non-metals. Most of the elements are metals. The crust of the earth is the biggest source of metals. Some soluble salts of metals are found in sea water. The atoms in a metal are bound together by metallic bonds.
CHEMICAL PROPERTIES OF METALS
Let us consider the reactions of metals with oxygen of air, chlorine, water and acids.
Reaction with oxygen of air :
Metals generally react with different components of the air. Different metals react in different ways under different conditions. They react with oxygen of air to produce their respective oxides. The following experiments will help you in understanding the reactions.
Experiment 1 :
Cut a small piece of sodium and place it on a watch glass. Do not do this without the supervision of your teacher. Observe the interior of the metal which has a shining surface. After sometime it turns dull and finally becomes powder. This powder is sodium carbonate. Sodium reacts with the component of air gradually to produce sodium carbonate. Sodium does not react with kerosene; this the reason for preserving sodium in kerosene.
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| Reaction of Sodium with Air |
When sodium burns in excess of oxygen, it produces sodium peroxide .
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| Reaction of Sodium with Excess of Oxygen |
Ex 1 Fig: Do not do this without the supervision of your teacher.
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| Sodium converts in Sodium Carbonate |
Experiment 2 :
Hold a piece of magnesium ribbon with tongs. Burn it in a flame. Magnesium burns brilliantly in air forming magnesium oxide.
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| Magnesium burns - Magnesium Oxide develops |
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| Magnesium Ribbon heated |
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| Magnesium Oxide develops on end of Ribbon |
Experiment 3 :
Take a foil of copper and heat it in a flame. Allow the foil to cool. After sometime a black layer is seen on the copper foil. The black layer so produced is an oxide of copper.
Take a foil of copper and heat it in a flame. Allow the foil to cool. After sometime a black layer is seen on the copper foil. The black layer so produced is an oxide of copper.
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| Copper Burns - Oxide of Copper developes |
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| Copper foils heated |
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| Copper foils - Oxide of Copper developes |
Experiment 4 :
Take three new iron nails.
Take three new iron nails.
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| Beaker with Anhydrous Calcium |
Place one of them in a beaker containing anhydrous calcium chloride (Fig).
Close the first beaker containing anhydrous calcium chloride, by a watch-glass. Air in the first beaker remains dry because of the presence of anhydrous calcium chloride placed in cotton cloth.
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| Beaker with Full of Water |
Immerse the second nail fully in water (Fig).
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| Beaker with half of water |
Place the third nail half immersed in water (Fig).
Observe the nails after a few days.
A brown layer is seen on the part of the nail which is exposed to air in the third beaker. The other two nails do not get brown coating.Observe the nails after a few days.
Remember:
Iron is protected from rusting by
coating it with zinc or by painting it . Iron pipes are protected by heating
and then dipping them in molten coals tar.
Why does the nail in the last beaker turn brown ?
This shows that air and water are required for iron to rust. The rust is hydrated oxide of iron. The chemical formula of rust is
This shows that air and water are required for iron to rust. The rust is hydrated oxide of iron. The chemical formula of rust is
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| Hydrated Oxide reaction Formula |
By the above experiments it is evident that different metals react with the component of air in different manner and at different rates and different conditions. There are some metals which do not reat with the components of air at all. They are gold and platinum.
Reaction of metals with water :
When metals react with water, hydrogen is liberated.
Experiment 5 :
Take a trough containing water. Gently drop a small piece of sodium on the surface of water with the help of a tong. It floats on water with a hissing sound. Bubbles of hydrogen are liberated. Sometimes hydrogen may catch fire and burn.
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| Sodium reacts with water - Hydrogen Bubbles liberated |
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| Sodium reacts with water - Hydrogen Bubbles liberated |
This experiment shows that sodium reacts with water vigorously to displace hydrogen. Similarly potassium and calcium displace hydrogen from water.
When steam is passed over hot iron, zinc or magnesium, hydrogen is liberated along with the formation of their respective oxides.
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| Zinc Oxide |
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| Magnesium Oxide |
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| Iron Oxide |
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| Students need |
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