METALS AND NON-METALS
CLASS:- 10TH MARKS:- 06
Metals are those elements which possess lusture when freshly cut and are malleable, ductile and good conductors of heat and electricity. These elements lose electron(s) and form cat ions so these are also called electropositive elements, e.g., sodium(Na), magnesium(Mg), potassium(K), copper(Cu), gold(Au) etc. These are used to make utensils, coins, wires, jewellery. These are used in the construction of bridges, buildings etc.
Non-metals are those elements which are non-malleable and non-ductile and generally do not conduct heat and electricity. Generally these elements gain electron(s) and form an ions so these are also called electronegative elements, e.g., hydrogen (H), oxygen(O), nitrogen(N) etc.
Q. What are the various physical properties of metals?
Following are the properties of metals and non-metals:
(i) Metals in the pure state possess lusture, i.e., a shiny surface.
(ii) Metals are generally hard except Li, Na, K.
(iii) Metals are ductile, i.e., they can be drawn into wires. This property of metals is called ductility. Gold is the most ductile metal.
(iv) Metals are malleable, i.e., they can be beaten into sheets. This property of metals is called malleability.
(v) Metals are good conductors of heat. Silver is the best conductor of heat whereas lead is the poorest conductor of heat.
(vi) Metals are good conductors of electricity. Silver is the best conductor of electricity whereas mercury is the poorest conductor of electricity.
(vii) Generally metals have high melting points except Li, Na, K, Ga, etc.
(viii) Generally metals are sonorous, i.e., they produce sound on striking with any hard object.
(ix) Metals have high tensile strength, i.e., load bearing capacity.
(x) Metals have high density except Li, Na, K. (xi) All metals are solids except mercury.
Q. What are the various physical properties of non-metals?
(i) Non-metals don’t possess lusture except iodine.
(ii) They are soft and brittle. Diamond is the hardest natural substance but is brittle.
(iii) They are neither malleable nor ductile.
(iv) They are non-sonorous.
(v) They have low melting and boiling points except diamond and graphite.
(vi) They have low density.
(vii) They bad conductors of heat except diamond.
(viii) They are bad conductors of electricity except graphite.
(ix) They may be solids, liquids and gases.
Q. What are the various chemical properties of metals?
Following are the chemical properties of metals:
(i) Metals are electropositive in nature.
(ii) They have low ionization energy.
(iii) They act as reducing agents.
(iv) Metals react with oxygen to form metal oxides which are basic or amphoteric in nature. E.g.,
2 Na + 1/2 O2 → Na2O 2Mg + O2 → 2MgO
(v) Some metals react with dilute acids and displace hydrogen of the acid forming salts, e.g., Na, K, Ca, etc. Some metals react with concentrated acids to produce salts and hydrogen gas while as some don’t react, e.g.,
Au, Pt. 2K + 2HCl → 2KCl + H2 Mg + H2SO4 → MgSO4 +H2
(vi) Reaction with water: Some metals react with water to form hydroxide or an oxide along with the evolution of hydrogen gas, e.g.,
2Na + 2H2O → 2NaOH +H2 Ca + 2H2O → Ca(OH)2 + H2
Q. What are the various chemical properties of non-metals?
(i) Non-metals are generally electronegative in nature.
(ii) They have high ionization energy.
(iii) They act as oxidizing agents
(v) Non-metals react with oxygen to form neutral or acidic oxides. CO2, SO2 etc. are acidic oxides and H2O, CO etc. are neutral oxides.
(vi) Reaction with hydrogen: Non-metals react with hydrogen to form covalent hydrides, e.g., methane, ammonia etc. N2 + H2 → 2NH3
(vii) Non-metals don’t react with dilute acids to produce hydrogen gas because they can’t displace hydrogen gas from acids.
(viii) Generally they don’t react with water to produce H2 gas because they can’t reduce H+ of water to hydrogen gas.
Q. What is a mineral?
Mineral is defined as the elementary state or the compound in the form of which the metals occur in nature. The earthy, sandy or rocky impurities associated with the mineral are called gangue or matrix.
Q. What is an ore?
The mineral from which metal can be extracted economically and conveniently is called an ore. All ores are minerals but all minerals are not ores. The ore of aluminum is called bauxite (Al2O3.2H2O), the ore of copper is called copper glance (Cu2S) etc.
Q. Why is sodium kept immersed in kerosene oil?
Sodium is very reactive metal, so it reacts with oxygen to form sodium oxide. It also reacts with moisture to form sodium hydroxide and hydrogen gas. The hydrogen gas thus produced sometimes catches fire.
4Na + O2 → 2NaO 2Na + 2H2O → 2NaOH + H2
To prevent the sodium metal and to prevent accidental fires, sodium is kept immersed in kerosene oil with which it doesn’t react.
Q. How do metals and non-metals react?
Metals and non-metals react by the transfer (i.e,loss and gain) of electrons from metals to non-metals. The compounds formed in such a way are known as ionic or electrovalent compounds, e.g., NaCl, MgO etc.
Q. What are amphoteric oxides?
Oxides which react with both acids and bases to form salt and water are called amphoteric oxides, e.g.,
ZnO + 2HCl → ZnCl2 + H2O
ZnO + 2NaOH → Na2ZnO2 + H2O
Q. What is the importance of metals and non-metals?
Metals are used in making utensils, bridges, automobile parts, coins, jewellery etc. Metals like Ti, Cr, Mn etc are used in country’s defence so these are called strategic metals.
Non-metals like carbon and hydrogen are present in proteins, carbohydrates, fats etc which are required for growth and maintenance of living organisms. Oxygen as we know is very essential for all living organisms for sustaining life, etc.
Q. What do you mean by extraction of metals?
Getting metal out of ore is called extraction of metal. The various steps involved in the extraction of metals from its ore followed by refining of the metal is called metallurgy.
Extraction of metals from ores: Different steps or techniques are used for obtaining metals from ores. These are: (a) Enrichment or concentration of ore. (b) Extraction of metals from ores. (c) Refining of metals.
(a) Enrichment of ore: Ores mined from the earth contain large amount of impurities such as sand, soil etc called gangue and these are in the form of big lumps. These are first broken into small pieces and then pulverized to fine powder. The first step in the metallurgy is to remove unwanted impurities. This is done by certain methods. The method is based on the differences between the physical or chemical properties of the gangue and the ore.
These methods are
(i) Gravity separation/ hydraulic washing.
(ii) Froth floatation process. (c) Electromagnetic separation. (d) Chemical separation.
(b) Extraction of metal from the concentrated ore:
This is based upon the nature of metal. Based on their reactivity, metals have been divided into three groups (i) Metals of low reactivity (ii) Metals of medium reactivity. (iii) Metals of high reactivity.
(i) Sulphide ores are common ores of low reactive metals. To obtain metals from these ores, roasting ( heating strongly the ore in presence of air) is done. As a result metal sulphide is first converted into metal oxide, which on further heating is reduced to metal, e.g.,
2HgS + 3O2 → 2HgO + 2SO2 then 2HgO + heat → 2Hg + O2
(ii) These metals are found in nature in the form of their oxides, sulphides or carbonates. As it is easier to reduce oxides than sulphides or carbonates. So, sulphides and carbonates are first converted into metal oxides.
Conversion of sulphide ores is done by roasting, e.g.,
2ZnS + 3O2 + heat → ZnO + SO2
Conversion of carbonate ores is done by calcination (heating strongly the ore in absence of air), e.g.,
ZnCO3 + Heat → ZnO + CO2
Reduction of metal oxide to metal: As these metals are moderately reactive, their oxides can’t be reduced by heating alone but it is done by using suitable reducing agents like carbon (coke), aluminium etc. The reduction of metal oxides by heating with coke is called smelting, e.g.,
ZnO + C + Heat → Zn + CO
The reduction of metal oxides using Al as reducing agent is called aluminothermy
Fe2O3 +2Al + ignited → 2Fe + Al2O3
The above reaction is used for welding the broken parts of iron machinery. This is known as thermite reaction.
(c) Refining of metals: The metal obtained after extraction of from the concentrated ore contains a number of impurities. It is called crude metal. The method of refining/purifying depends upon the nature of metal and impurities. The most common method is electrolytic refining in which impure/crude metal is made anode, pure metal is made cathode and a water soluble salt of the metal is taken as electrolyte in the electrolytic tank. Impure metal dissolves from the anode and is deposited on the cathode. Impurities fall below the anode as anode mud. In this way crude metal gets purified.
Q. What are alloys?
An alloy is a homogenous mixture of two or more metals or metals and non-metals, e.g, brass(Cu 80%, Zn 20%), bronze(Cu 90%, tin10%), stainless steel(iron 78%, Cr 18%, Ni 8%) etc.
Alloys are prepared to develop certain specific properties which are not possessed by the constituent elements. The main objectives of making alloys are:
(i) To increase hardness. (ii) To increase resistance to corrosion. (iii) To increase tensile strength. (iv) To modify color etc. (v) To increase electrical conductivity.
Q. Name two metals that are found in free state.
Platinum and gold
Q. What chemical process is used for obtaining a metal from its oxide?
Metal is obtained from its oxide by reduction.
Q. Which metals do not corrode?
Platinum , gold etc do not corrode easily.
Q. Why do ionic compounds have high melting points?
Because of strong electrostatic forces of attraction between cations and anions.
Q. Explain the meaning of malleable and ductile.
Substances that can be beaten into sheets are called malleable and the substances that can be drawn into wires are called ducticle. Metals are malleable and ductile.
Prepared By : Kifayat Hussain