INTRODUCTION-In our daily life we come across many objects and materials. These objects are different from each other in appearance and hardness. Those objects which are very hard and have shiny appearance are generally objects made up of metals. Those objects which are not very hard and dull in appearance are made up of non-metals.
Activity 4.1 Knowledge of Appearance and Hardness of Some materials– In this activity a number of metallic and non-metallic objects were collected and observations were made to differentiate on the basis of their appearance and hardness.
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Object/ Material |
Appearance(Shiny/Dull) |
Hardness (Very hard/Not very hard) |
|
Copper |
Shiny |
Very hard |
|
Coal Piece |
Dull |
Not very hard |
|
Aluminium |
Shiny |
Very hard |
|
Sulpher |
Slightly Shiny |
Not very hard |
|
Iron (New Object) |
Shiny |
Very hard |
|
Sodium |
Shiny on cutting |
Not very hard |
The metals are different from non-metals on the basis of their physical and chemical properties. Those characteristics which can be seen and measured denote physical properties. Physical properties are related with the shape, size, colour and state of the objects. Those characteristics which cannot be seen and cannot be measured are called as chemical properties. They are permanent and specific characteristics unless some chemical changes are not carried.
PHYSICAL PROPERTIES OF METALS AND NON-METALS – The measurable and external observable properties of any object are called it’s physical properties. Let’s learn more about these physical properties of metals and non-metals.
1. Physical state-Metals are found in solid state due to strong inter-molecular forces. Exception- Mercury (Hg) is a metal found in liquid state. Non-metals are found in liquid and gaseous state generally. Except-Iodine (I), it is found in solid state.
2. Malleability– The metal objects can be beaten hard with a hammer to change them into their thin sheet. This changing is not possible with non-metals as they break into small pieces. The property of metals by which they can be converted into thin sheen by hammering is called malleability. E.g.- Silver, Gold, Copper etc are malleable while Coal, Sulpher etc are non-malleable.
 |
| Beating /hammering of iron nails to observe malleability |
3. Ductility– The conducting wires which we see are made up of metals. The property of metals by which they can be drawn into thin wires is called ductility. Non-metals cannot be drawn into thin wires.
4. Sonority– Metal bells in the temple and church produce ringing sound on striking hard. This property is called sonority. The metals are sonorous while non-metals are not sonorous.
5. Hardness– Metal objects are hard to break because of strong metallic bonds. Non-metals easily break because of less inter-molecular forces among their molecules. Exception- Mercury (Hg) is a metal found in liquid state.
6. Metallic Shine (lusture) – The metals have their characteristic shine. The non-metals do not have such a characteristic shine. When a piece of sodium metal is cut with sharp knife, that characteristic shine can be seen. We often seen this shine on objects made up of steel, copper, brass, aluminium, iron etc.
7. Conductivity of heat and electricity– The metals are good conductors of heat and electricity. Non-metals are poor conductors of heat and electricity. Exception- Graphite is an allotrope that carbon. It is commonly seen in the graphite pencils. It is a conductor of current. Non-metals are insulators of heat and electricity.
Those materials which are hard, lustrous, malleable, ductile, sonorous and good conductors of heat and electricity are called as metals. E.g. – Iron (Fe), Aluminium (Al), Zinc (Zn), Gold (Au), Silver (Ag), Sodium (Na), Potassium (K), Magnesium (Mg) etc. Those materials which are not hard, non-lustrous, non-malleable, non-ductile, non-sonorous and poor conductors (insulators) of heat and electricity are called as non-conductors. E.g. – Oxygen (O), Iodine (I), Sulpher (S), Chlorine (Cl), Carbon (C), Phosphorus (P), Argon (Ar), Neon (Ne)etc.
CHEMICAL PROPERTIES OF METALS AND NON-METALS– Metals and non-metals react with many elements and compound to form new products. This occurs by chemical reactions. Chemical reactions lead to permanent change and are not irreversible unlike physical changes. Below are some of the chemical reactions in which reactions of metals and non-metals have been explained.
1. Reaction with oxygen– Rusting of iron is common chemical reaction in which iron reacts with oxygen to form the rust.
Iron + Oxygen + water vapour–> Rust ((Hydrated Ferrous Oxide)
Or, Fe + O2 + H2O –> Fe2O3.xH2O
The burning of magnesium ribbon is also an example of reaction of metal with oxygen.
Magnesium + Oxygen –> Magnesium oxide
Or, Mg + O2 –> MgO
Both these above reactions are example of oxidation reaction in which oxygen is combining with other element. The metal oxides are formed as a result of reaction of metal and oxygen. Generally, the metal oxides are basic in nature. On dissolving in water metal oxides form their alkali. The alkali turns red litmus in to blue colour.
Rusting occurs in presence of oxygen and moisture i.e. water vapours. Near sea shores the rate of rusting increases. Rusting causes great economic loss as the bridges, iron objects, vehicles etc get rusted gradually. Alloy formation, galvanization, chromium plating, applying paint, oil and grease are common methods to prevent rusting. Rusting occurs in copper, brass and silver also. The copper utensils often get coated with a dull green coating. This coating is a mixture of copper hydroxide and copper carbonate.
Copper + Oxygen + Water vapour + Carbon dioxide –> copper hydroxide + copper carbonate
Or, Cu + O2 + H2O + CO2 ——-> Cu (OH) 2 + CuCO3
The silver develops a black coating in moist and polluted areas. The polluted air contains Sulpher which combines with silver to form silver sulphide (Ag2S). Hydrogen sulphide (H2S) gas contains Sulpher.
Silver + Hydrogen Sulphide + Oxygen + Water Vapour –> Silver sulphide + Hydrogen
Or, 2 Ag + H2S + O2 + H2O —> Silver sulphide (Ag2S) + H2
All the above are example of corrosion in iron, copper and silver metals. So, the corrosion tarnishes the metals.
The non-metals like Sulpher react with Oxygen to produce Sulpher dioxide gas. This reaction requires heating of Sulpher. Generally, the oxides of non-metals are acidic in nature. When Sulpher dioxide reacts with water, sulphurous acid is formed. The sulphurous acid turns blue litmus paper into red.
Sulpher + Oxygen –> Sulpher dioxide gas
Or, S + O2 –> SO2
Sulpher dioxide (SO2) + Water (H2O) –> sulphurous acid (H2SO3)
|
S.N. |
Base or Alkali |
Formula |
Metal |
|
1 |
Sodium Hydroxide |
NaOH |
Sodium |
|
2 |
Potassium Hydroxide |
KOH |
Potassium |
|
3 |
Calcium Hydroxide |
Ca(OH)2 |
Calcium |
|
4 |
Magnesium Hydroxide |
Mg(OH)2 |
Magnesium |
|
5 |
Aluminium Hydroxide |
Al(OH)3 |
Aluminium |
|
S.N. |
Acid |
Formula |
Non-metal |
|
1 |
Sulphuric Acid |
H2SO4 |
Sulpher |
|
2 |
Nitric Acid |
HNO3 |
Nitrogen |
|
3 |
Phosphoric Acid |
H3PO4 |
Phosphorus |
|
4 |
Sulphurous Acid |
H2SO3 |
Sulpher |
|
5 |
Nitrous Acid |
HNO2 |
Nitrogen |
2. Reaction with water- Some metals react very slowly with water while some react vigorously. Iron reacts very slowly while Sodium reacts vigorously with water vapour and water to form sodium hydroxide and a lot of heat is released in this reaction. So, Sodium is stored in kerosene.
Sodium (Na) +Water (H2O) —> Sodium hydroxide (NaOH) + Heat
Non-metals generally do not react with water. However, Phosphorus is very reactive with oxygen. So, it is stored in water.
3. Reactions with acids- Acids are organic and inorganic. Here reaction of inorganic acids with metals has been discussed. Some metals do not react with dilute acids like dilute Hydrochloric acid (HCl) even on heating but reacts with sulphuric acid which is strong comparatively. When a more reactive metal reacts with an acid, hydrogen gas is released. To confirm this when a burning match stick is brought near hydrogen gas, ‘POP’ sound can be heard. In this regard, reactivity series of metals is very important to understand.
REACTIVITY SERIES OF METALS–
Potassium k Most reactive metal
Sodium Na
Lithium Li
Barium Ba
Strontium St
Calcium Ca
Magnesium Mg
Aluminium Al
Manganese Mn
Zinc Zn
Chromium Cr
Iron Fe
Cadmium Cd
Cobalt Co
Nickel Ni
Tin Sn
Lead Pb
Hydrogen H
Antimony At
Bismuth Bi
Copper Cu
Silver Ag
Gold Au
Platinum Pt Least reactive metal
4. Reaction with bases- Metals reacts with bases or alkali to produce hydrogen gas. When a burning match stick is brought near it, highly inflammable hydrogen catches fire and POP sound can be heard. Metal + Base (alkali) —–> Metallic compound + Hydrogen gas
The reactions of non-metals with alkali are very complex.
5. Displacement Reactions- The metal above in the reactivity series of metals displaces the metal lower in reactivity series from its compound. This reaction is called displacement reaction. E.g.-
Copper Sulphate (Blue) + Zinc (Zn) –> Zinc Sulphate (Colourless) + Copper (Red)
Or, CuSO4 + Zn –> ZnSO4+ Cu
In this reaction the blue colour of copper sulphate solution turns colourless on adding zinc metals. The copper metal being less reactive than zinc gets displaced from its compound. The copper can be seen deposited on the zinc granules.
USES OF METALS AND NONMETALS- Following are the uses of metals and non-metals.
Uses of metals-
1. Iron – It is used to prepare nails, tools, door, grill, vehicles, machinery, etc. The brittle pig iron is used for making pipes, sinks, Sockets etc. The pig iron objects are prepared by casting. Wrought iron is a malleable form of iron in which little amount of carbon is found. Stainless steel is used to prepare utensils, containers, knives, machinery tools etc.
2. Aluminium- It is used for making cookwares and foils for food packing. The electric cables are used to transmit the current.
3. Copper- It is used in making of electric wires, heating utensils, kitchen wares, calorimeter, car radiator etc. Brass (Copper + Zinc), Bronze (Copper + Tin + Aluminium + Manganese + Nickel/ Zinc +Arsenic / Phosphorus/ Silicon), German Silver (Copper + Zinc + Nickel) alloys contain copper.
4. Zinc– It is used to prepare alloys like-brass, bronze and German Silver. Zinc is used in the galvanization of iron objects to prevent rusting. In dry cells, zinc is used to make negative terminal.
5. Mercury– It is used in thermometers, barometers, sphygmomanometers etc.
6. Tin– It is used for making of containers and alloy like bronze. Sometimes tin is also mixed in brass.
7. Lead– It is used to prepare alloys, electrodes of batteries etc.
8. Antimony– It is used to prepare fire proof materials, enamels, paints, glass, ceramics, pottery etc.
9. Cobalt- It is used to make alloys for aircraft engines. Cobalt is used in batteries and in electroplating. An isotope of cobalt C-60 is used in treatment of cancer.
10. Gold, Silver and Platinum are used in jewellery making.
Uses of nonmetals-
1. Oxygen is inhaled by living organisms during respiration.
2. Carbon dioxide gas is used by green plants during photosynthesis.
3. Carbon- is found in all organic compounds. Graphite is an allotrope of carbon. Graphite is used in lead of pencils, as lubricant of machines and as electrode in dry cells.
4. Phosphorus- It is used in firecrackers, fertilizers, etc.
5. Hydrogen- It is used in welding as oxy-hydrogen flame, extraction of metals, preparing fertilizers, manufacture of ammonia by Haber method etc.
6. Sulpher– It is used in vulcanization of rubber, preparation of sulphuric acid, and skin ointment. It is used as insecticides and fungicides.
7. Silicon– It is used in preparing computer, electronic items, solar cells, transistors, microchips etc.
EXERCISE QUESTIONS SOLVED
Q.1 Which one of the following can be beaten into thin sheets?
(a) Zinc (b) Phosphorus
(c) Sulpher (d) Oxygen
Ans-(a) Zinc
Q.2 Which one of the following statements is correct?
(a) All metals are ductile.
(b) All non-metals are ductile.
(c) Generally, metals are ductile.
(d) Some non-metals are ductile.
Ans- (a) All metals are ductile
Q.3 Fill in the blanks:
(a) Phosphorus is a very …………………..non-metal.
(b) Metals are ………………conductor of heat and ………….. .
(c) Iron is ………..reactive than copper.
(d) Metals react with acids to produce ……………… gas.
Ans- (a) reactive (b) good, electricity (c) more (d) hydrogen
Q.4 Mark ‘T’ if the statement is true and ‘F’ if it is false.
(a) Generally, non-metals react with acids. ( )
(b) Sodium is a very reactive metal. ( )
(c) Copper displaces zinc from zinc sulphate solution. ( )
(d) Coal can be drawn into wires. ( )
Ans- (a) False (b) True (c) False (d) False
Q.5 Some properties are listed in the following table. Distinguish between metals and non-metals on the basis of these properties.
|
Properties |
Metals |
Non-metals |
|
1. Appearance |
|
|
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2. Hardness |
|
|
|
3. Malleability |
|
|
|
4. Ductility |
|
|
|
5. Heat conduction |
|
|
|
6. Conduction of electricity |
|
|
Ans-
|
Properties |
Metals |
Non-metals |
|
1. Appearance |
Shiny/Lustrous |
Dull |
|
2. Hardness |
Hard |
Not so hard |
|
3. Malleability |
Malleable |
Brittle |
|
4. Ductility |
Ductile |
Non-ductile |
|
5. Heat conduction |
Good Conductors |
Insulators / Poor conductors |
|
6. Conduction of electricity |
Good Conductors |
Insulators |
Q.6 Give reason for the following:
(a) Aluminium foils are used to wrap food items.
(b) Immersion rods for heating liquids are made up of metallic substances.
(c) Copper cannot displace zinc from its salt solution.
(d) Sodium and potassium are stored in kerosene.
Ans- (a) Aluminium are malleable. Their foils are made and they are not so costly. So, aluminium foils are used to wrap food items.
(b) Immersion rods are made up of metals which are good conductor of heat and current.
(c) Copper is less reactive metal than zinc. So, copper cannot displace zinc from its solution.
(d) Sodium and potassium are very reactive metals. They react quickly with air and moisture of the atmosphere. Therefore, they are kept in kerosene not to catch the fire.
Q.7 Can we store lemon pickle in an aluminium utensil? Explain
Ans- Aluminium reacts with citric acid of lemon to produce hydrogen gas. The citric acid corrodes the wall of the aluminium utensils. So, the lemon pickles are not stored in aluminium utensils.
Q.8 Match the substances given in column I with their uses given in column II.
Column I Column II
(i) Gold (a) Thermometers
(ii) Iron (b) Electric wire
(iii) Aluminium (c) Wrapping food
(iv)Carbon (d) Jewellery
(v) Copper (e) Machinery
(vi)Mercury (f) Fuel
Ans- (i) – d (ii) – e (iii) – c (iv) – f (v) – b (vi) –a
Q.9 What happens when-
(a) Dilute sulphuric acid is poured on a copper plate?
(b) Iron nails are placed in copper sulphate solution? Write word equations of the reactions involved.
Ans- (a) Copper is a very less reactive metal. But, dilute sulphuric acid reacts with copper to release copper sulphate and hydrogen gas is released.
Copper + Sulphuric acid (dilute) –> Copper sulphate + Hydrogen gas
(b) Iron is more reactive metal than copper. So, it displaces copper from copper sulphate solution. Thus, the colour of copper sulphate changes from blue to light green as a result of formation of iron sulphate.
Copper Sulphate (Blue) + Zinc (Zn) –> Zinc Sulphate (Colourless) + Copper (Red)
Q.10 Saloni took a piece of burning charcoal and collected the gas evolved in a test tube.
(a) How will she find the nature of the gas?
(b) Write down the word equations of all the reactions taking place in this process.
Ans- (a) Charcoal contains carbon. On burning, the gas produced in maximum quantity will be CO2. To confirm it the gas produced by burning charcoal is passed to lime water in controlled conditions of laboratory. The lime water if turns milky white in colour then the gas evolved will be carbon dioxide.
(b) Charcoal (C) ——burning—-> gas ——–> Lime water ——-> Milky white.
Q .11 One day Reeta went to a jeweller’s shop with her mother. Her mother gave old gold jewellery to the goldsmith to polish. Next day when they brought the jewellery back, they found that there was a slight loss in it’s weight. Can you suggest a reason for the loss in the weight?
Ans- The cleaning of gold jewellery is done in aqua regia (a mixture of concentrated nitric acid and hydrochloric acid). Aqua regia is very strong that can dissolve the gold. So, during cleaning some gold had dissolved and as a result there is loss in the weight of gold jewellery.
CHECK YOUR PROGRESS- 5 x 5 = 25 Marks Time =40 Minutes
Q.1 Define the terms- Malleability, ductility and sonorous.
Q.2 Explain the reaction of metals with oxygen with two suitable examples.
Q.3 What happens when sodium reacts with water?
Q.4 Write the reaction when zinc reacts with hydrochloric acid.
Q.5 What is displacement reaction? Give a suitable example.
GROUP PROJECTS-
1. Collect the different types of items made up of metals. Write the metal or combination of metals in that.
2. Write the Process of sulphurous acid preparation and how it’s test is done.
3. Prepare a group project on uses of metals.
4. Prepare a group project on uses of non-metals.
5. Explain the reactivity series of metals. Why hydrogen is kept in this series?