METAL AND NON METALS # ELEMENT Definition An element is a pure substance which is made up of same kind of atom which differs from their physical and chemical properties. 115 elements are known under which 92 are naturally occurring. Classification of elements Elements can be classified into 3 types • • •
Metals Non metals Metalloids CLASSIFICATION OF ELEMENTS
METALS
FREE STATE GOLD SILVER
METALLOIDS
COMBINED STATE
NON METALS
silicon, germanium, arsenic
NA, K, Ca in the form of catbonate , oxides, sulphide
PLATINUM
Some abundant elements • Aluminium(most) • Iron • Most abundant non metal • Oxygen Less reactive metal • Gold • Silver • Platinum Most reactive metals • Sodium • Potassium • Calcium
FREE STATE
Oxygen, Nitrogen, sulphur, Carbon in the form of graphite, diamond.
COMBINED STATE
Sulphur and carbon in the form of oxides, carbonates , sulphides
Non metal existing in free(native) and combined state • Sulphur • Carbon
DIFFERENCE BETWEEN MINERAL AND ORE Mineral A mineral is a naturally occurring inorganic substance found deep inside the earth surface
ore Ore is a mineral from which one or more metals can be extracted economically and profitably.
Examples of ore Ore of Iron – Hematite ( Fe2O3) ; Magnetite( Fe3O4) Ore of aluminium – bauxite( Al2O3.H2O) ; Cryolite (Na3AlF6)
METALLURGY DEFINATION Sequence of processes to extract a metal in its pure form from its ore is called metallurgy. STEPS OF METALLURGY STEP 1 CONCENTRATION OF ORE
STEP 2 REDUCTION
METALLURGY
STEP 3 REFINING OF METAL
• • •
CONCENTRATION OF ORE It is the process of removal of impurities from its ore. REDUCTION It is the process of the reduction of the metal ire to get the metal in its free state. REFINING OF METAL The metal obtained in the second step is impure. Refining is the process of purification of metal.
Physical properties Property
Metal
Non metal
Physical state
Are generally solids except mercury(liquid state)
Lusture
Have shiny appearance
Melting & Boiling point
High mp.pt and bp.pt Exception Cesium has mp.pt of 28.70c
Occur in • Solids- carbon, sulphur, phosphorous. • Liquid- bromine • Gas- oxygen, nitrogen Dull appearance Exception • Graphite • Iodine Low mp.pt & bp.pt
Hardness
Density
Very hard & can withstand high pressure. Exception Na & K are soft and can be easily cut by knife. High
Ductility
Metals are ductile
Exception Carbon has high mp.pt of 37230c Soft Exception Diamond, hardest known substance. Low Non ductile.
Ductility is defined as the property of metals to be drawn into thin wires. Most ductile metals Gold & silver.
Malleability
Metals are malleable
Non ductile
Malleability is defined as the property of metals to be drawn into thin sheets on hammering. Most malleable Gold and silver
Conductivity • Thermal conductivity •
Electrical conductivity
Property of metals that allows conduction of heat from one region to another.
Bad conductor of heat Exception Graphite
Property of metals that allows conduction of Bad conductors of current electricity from one region to another. Exception Graphite(form of carbon)
Exception Lead and mercury are bad conductors
Sonorosity
Property of metals to produce a ringing sound when struck.
NON SONOROUS
METALLOIDS There are some metals which show some properties of a metals and non metals. Such elements are called metalloids. Examples: ARSENIC, GERMANIUM, SILICON
NOBLE METALS Definition Those metals that have least reactivity and do not react with air, water, acids and bases are referred to as noble metals. Two noble metals are: GOLD, PLATINUM Q why noble metals do not get tarnished?
Q silver jewellery when kept in open gets tarnished after some time. Why?
Pure gold is soft and its purity is measured in units called CARATS. If gold is 22 carats pure, it means that 22 parts of gold are present in 24 parts of mixture of gold with copper and silver. Copper and silver are added to make pure gold hard. Q why gold is alloyed with silver and copper?
USES OF METALS. ALUMINIUM USE In electrical cables
• • • •
In making cooking utensils Making aluminum foils
To make alloys like duralumin(for making aircraft)
• •
PROPERTY Good conductor Ductile (can be drawn into thin wires.) Good conductor of electricity. Malleable(can be beaten into thin sheets on hammering) Good conductor of heat Light and strong
COPPER USE In electrical cables
• • •
In making cooking utensils
PROPERTY Good conductor Ductile (can be drawn into thin wires.) Good conductor of electricity.
# GENERAL USES OF METALS For making electrical fittings, net doors, wires as metals are ductile. Gold, silver, platinum are used fir making jewellery because of its lusture, ductility and malleability. Are used for making bells, because of the property of sonorosity, which gives ringing sound when struck. Iron is used for making cooking utensils, water boilers, and chains because of its strength, malleability, ductility and versatility.
CORROSION # DEFINITION Eating away of metals is called corrosion. # Conditions for corrosion to occur • •
Presence of air Presence of water.
# RUSTING It is the type of corrosion which occurs due to the formation of brown colored layer of iron oxide called rust formed on iron when exposed to moist air. Chemical Formulae
Fe2O3 .XH2O
Chemical reaction
Iron + water + oxygen Fe(s) + 3O2(g)+ XH2O
→
hydrated iron (III) oxide 2Fe2O3 .XH2O(s)
Aluminium does not rust - corrode. Its surface is protected by a natural layer of aluminium oxide. This prevents the metal below from coming into contact with air and oxygen. COPPER when comes in contact with moist air containing O2 and CO2, it forms green coating of basic copper carbonate. ( CuCO3.Cu(OH)2 ) #To study the conditions necessary for corrosion to occur. Take three test tubes A, B, C and put iron nails in each of the test tubes. In test tube A fill it half with tap water. In test tube B add boiling water and pour oil over it. In test tube C add anhydrous calcium chloride(cacl2) Observation Test tube
Observation
A
Rusting occurs
B
No rusting occurs
C
No rusting occurs
inference Since it has both air & water. Iron reacts to form Fe2O3 .XH2O (rust) Since the boiled water expels the air from it and oil layer prevents further reaction with air. anhydrous calcium chloride (cacl2) absorbs the moisture from the air present in the test tube. So in the absence of air no rusting occurs
ACTIVITY TO SHOW HOW RUSTING OCCURS # WAYS TO PREVENT CORROSION ⇒ Oiling and greasing It cuts off the contact between the metal and moist air and prevents it from rusting. ⇒ Painting Paint also cuts off the contact between the metal and moist air and prevents it from rusting. ⇒ Galvanization It is the process of coating the surface of iron with the layer of zinc metal. This is done by dipping the iron objects into molten zinc. ⇒ Electroplating It is the process of depositing thin layer of another lesser reactive metal like tin or chromium on its surface with help of electric current. ⇒ Alloying Iron on alloying with nickel and chromium, forms stainless steel which is resistant to corrosion
# ALLOYS DEFINITION An alloy is a homogenous mixture of metal and a metal or a metal and a non metal.
Advantage of alloy over metal ⇒ Alloys are corrosion resistant. For eg Iron when mixed with chromium and nickel forms stainless steel which is corrosion resistant. ⇒ Alloys are hard and have strength. For eg pure gold is soft but when mixed with copper or silver becomes hard. ⇒ Alloys are chemically resistant. ⇒ Have low melting point. For eg SOLDER alloy of lead and tin have low melting point than the metal.
SEE TABLE 3 FROM PAGE NO 75
