1. Metals-
ü Metals are described as elements of the periodic table that readily lose valence electrons (outermost electrons) to form positive ions called as cations.
ü For example we have -Aluminium, copper, iron, tin, gold etc.
ü Around 90 of the total 118 elements of the periodic table are metals.
ü Following are the properties of metals-
n Hard and have a high tensile strength
n Solids at room temperature, except mercury, which is liquid at room temperature.
n Malleable, i.e., can be beaten into thin sheets
n Ductile, i.e., can be drawn into thin wires
n Sonorous and Lustrous
n Good conductors of heat and electricity
n High melting and boiling points (except Cesium and Gallium)
n Dense, (except alkali metals).
n Osmium – highest density and lithium – least density
n Silver-grey in colur, (except gold and copper)
2. Non Metals-
ü Non-metals are those elements of the periodic table which have tendency to gain electron(s) in their valence shell (outermost shell).
ü They do not exhibit the properties of metals.
ü For example we have Carbon, Boron, etc.
ü Following are the uses of non metals-
n Non-metal is essential for our life which all living beings inhale during breathing,
n Non-metals used in fertilizers to enhance the growth of plants,
n Non-metal used in water purification process,
n Non-metal used in the purple colored solution which is applied on wounds as an antiseptic,
n Non-metals used in crackers.
Properties | Metals | Non-Metals |
Conductivity | Metals (such as iron or copper) are good conductors of heat and electricity. | Non-metals (such as coal or sulphur) are poor conductors of heat and electricity. Graphite is an exception as it is a good conductor of electricity. |
Ductility | Metals (such as aluminium and copper) are ductile, which means that they can be drawn into wires. | Non-metals are brittle (break down when struck) and hence, they cannot be drawn into wires. |
Hardness | All metals are hard though there are some exceptions. Sodium and potassium are soft and can be cut with a knife. | Most non-metals are soft. Diamonds are exceptions as they are the hardest material found on Earth. However, they are also very brittle and break when struck with a hammer. |
Lustre | Metals (such as gold, silver and copper) are lustrous, which means that they reflect light from their surface and can be polished. | Non-metals (such as coal) are generally dull and do not reflect light. Hence, they lack metallic lustre. |
Malleability | Metals (such as silver and aluminium) are malleable, which means that they can be beaten into thin sheets. | Since non-metals break easily, they cannot be pounded into sheets. |
Physical State | Most metals remain solid at room temperature, except mercury and gallium which remain liquid at room temperature. | Most non-metals exist in two of the three states of matter at room temperature: Gases (such as oxygen), and Solids (such as carbon). |
Sonorous | Metals produce ringing sounds when they are struck and hence, they are sonorous, except Mercury which is liquid in nature. | Non-metals are non-sonorous and do not produce the typical metallic sound when they are struck. |
Examples | Iron, copper, aluminium, calcium, magnesium, etc. | Sulphur, carbon, oxygen, phosphorus, etc. |
Table 01- Difference between metal and non metals
3. Important Chemical Reactions-
(i) Chemical Equation For Green Coating On Copper
Copper (Cu) + Moist Air (Water (H2O) + Oxygen (O2) + Carbon Dioxide (CO2))
→
Copper Hydroxide (Cu(OH)2) + Copper Carbonate (CuCO3)
2Cu + H2O + CO2 + O2 → Cu (OH)2 + CuCO3
ü Copper carbonate and copper hydroxide are basic in nature.
ü This green coating can be copper chloride if the copper reacts with sea air, or copper acetate if the copper reacts with acetic acid.
(ii) Reaction of Metals with Oxygen- When metals react with oxygen, they form metal oxide.
Metal + O2 → Metal Oxide
For Example-
Copper + Oxygen → Copper Oxide (black)
2Cu + O2 → 2CuO
Aluminium + Oxygen → Aluminium Oxide
4Al + 3O2 → 2Al2O3
Magnesium + Oxygen → Magnesium Oxide
2Mg + O2 → 2MgO
(iii) Reactions Involving Amphoteric Oxides- Some metal oxides react both with acids and bases to produce salts and water.
Aluminium Oxide + Hydrochloric Acid → Aluminium Chloride + Water
Al2O3 + 6HCl → 2AlCl3 + H2O
Aluminium Oxide + Sodium Hydroxide → Sodium Aluminate + Water
Al2O3 + 2NaOH → 2NaAlO2 + H2O
(iii) Reaction Of Metals With Water-
Metal + (cold) Water → Metal hydroxide + Hydrogen
Metal + Stream → Metal oxide + Hydrogen
Sodium + Water → Sodium Hydroxide + Hydrogen + Heat
2Na + 2H2O → 2NaOH + H2 + Heat
Calcium + Water → Calcium Hydroxide + Hydrogen
Ca + 2H2O → Ca(OH)2 + H2
Magnesium + Water → Magnesium Hydroxide + Hydrogen
Mg + 2H2O → Mg(OH)2 + H2
Aluminium + Water → Aluminium Oxide + Hydrogen
2Al + 3H2O → Al2O3 + 3H2
Iron + Water → Iron Oxide + Hydrogen
3Fe + 4H2O → Fe3O4 + H2
(iv) Reaction Of Metals With Solutions Of Other Metal Salts
Metal A + Salt Solution of Metal B → Salt Solution of Metal A + Metal B
ü More reactive metals replaces less reactive metals.
ü Less reactive metals cannot replace more reactive metals.
Iron + Copper Sulphate → Iron Sulphate + Copper
Fe + CuSO4 → FeSO4 + Cu
NCERT PRACTICE QUESTIONS
1. Which of the following can be beaten into thin sheets?
(a) Zinc (b) Phosphorus (c) Sulphur (d) Oxygen
Ans.- a) Zinc
Reason- Zinc is a metal with malleability and ductility whereas Phosphorus, Sulphur and Oxygen are nonmetals which lack malleability and ductility.
2. Which 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.- (c) Generally, metals are ductile.
Reason- Ductility is a property where a substance can be drawn into thin wires, Generally, metals are ductile with mercury as the exception.
3. Fill in the blanks.
(a) Phosphorus is a very _________non-metal.
(b) Metals are conductors 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
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
5. Some properties are listed in the following table. Distinguish between metals and non-metals on the basis of these properties.
Ans.-
Properties | Metals | Non-metals |
1. Appearance | Lustrous | Dull |
2. Hardness | Hard | Soft |
3. Malleability | Have property of Malleability | Do not have a property of Malleability |
4. Ductility | Have property of Ductility | Do not have the property of Ductility |
5. Heat Conduction | Good conductor of Heat | Bad Conductor of Heat |
6. Conduction of Electricity | Good conductor of Electricity | The bad conductor of Electricity |
6. Give reasons 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 is malleable and can be drawn into thin sheets hence Aluminium foils are used to wrap food items
b) Immersion rods for heating liquids are made up of metallic substances because metals are good conductors of heat and electricity.
c) Copper cannot displace zinc from its salt solution because Zinc is more reactive than copper.
d) Sodium and Potassium are highly reactive metals which readily reacts with atmospheric Oxygen to catch fire hence Sodium and Potassium are stored in kerosene.
7. Can you store the lemon pickle in an aluminium utensil? Explain.
Ans.- Pickle consists of acids which react with Aluminium metal to produce salt and Hydrogen. Hence pickle is not stored in aluminium utensil.
8. Match the substances given in Column A with their uses given in Column B.
Ans.-
A | B |
(i) Gold | (d) Jewellery |
(ii) Iron | (e) Machinery |
(iii) Aluminium | (c) Wrapping food |
(iv) Carbon | (f) Fuel |
(v) Copper | (b) Electric wire |
(vi) Mercury | (a) Thermometers |
9. What happens when
(a) Dilute sulphuric acid is poured on a copper plate?
(b) Iron nails are placed in a copper sulphate solution?
Write word equations of the reactions involved.
Ans.-
(i) No reaction occurs when dilute sulphuric acid is poured on a copper plate. However, when concentrated sulphuric acid is poured on a copper plate, hydrogen gas evolves along with the formation of blue colored copper sulphate crystals. The chemical reaction for the reaction between concentrated sulfuric acid and copper is-
Cu + H2SO4 (conc.) → CuSO4 + H2
ii) Iron being more reactive displaces copper from copper sulphate. In this reaction, the blue colour of copper sulphate fades and there is a deposition of copper on the iron nail.
Fe + CuSO4 → FeSO4 + Cu
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 word equations of all the reactions taking place in this process.
Ans.- a) In a test tube containing gas, add a few drops of water. Now cover the test tube and shake well. After shaking, test the solution with blue litmus. It will change from blue to red. Thus, gas is acidic in nature.
b) Charcoal reacts with oxygen to form carbon dioxide gas.
11. One day Reeta went to a jeweler’s shop with her mother. Her mother gave old gold jewelry to the goldsmith to polish. Next day when they brought the jewelry back, they found that there was a slight loss in its weight. Can you suggest a reason for the loss in weight?
Ans.- In order to polish the gold ornament, it is to be dipped into a liquid called aqua regia (a mixture of hydrochloric acid and nitric acid). On getting dissolved in the environment of aqua regia, the outer layer of gold dissolves and an inner shiny layer appears. The dissolving of the layer causes a reduction in the weight of the jewelry.
Junior Science Topic - Materials- Metals And Non Metals. Chapter notes, video lectures, power point presentation and NCERT exercise solution. (Class 8, CBSE syllabus, chapter 04)
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