CBSE Class 10 Chemistry Metals And Non Metals Worksheet Set L

 

METALS & NONMETALS

Physical properties of metals and non-metals:

Exceptions in Physical Properties

1. Graphite, a non-metal, is a good conductor of electricity.

2. Iodine is a lustrous non-metal.

3. Diamond, an allotrope of carbon, which is a non-metal is the hardest substance while sodium and potassium, being metals are soft enough to be cut by knife.

4. Mercury, which is a metal, is liquid at room temperature while rest are solids.

5. Sodium, potassium, mercury, caesium and gallium are metals with low melting and boiling points.

6. Diamond is the non-metal with high melting and boiling point.

7. Sodium, potassium and lithium are metals with low density.

Chemical properties of Metals

1. Reaction with oxygen:

Almost all metals combine with oxygen to form metal oxides.

Metal + Oxygen → Metal oxide

e.g. 2Cu + O₂ → 2CuO

• Metal oxides are basic in nature. Some metal oxides, such as aluminium oxide, zinc oxide, etc., which react with both acids as well as bases to produce salts and water are known as amphoteric oxides.

e.g. Al₂O₃ + 6HCl → 2AlCl₃ + 3H₂O
      Al₂O₃ + 2NaOH → 2NaAlO₂ + H₂O

• Most metal oxides are insoluble in water but some dissolve to form alkalis like sodium and potassium oxides.

• Metals such as potassium and sodium react so vigorously with oxygen that they catch fire if kept in the open. So to protect them they are kept immersed in kerosene oil.

e.g. Na₂O(s) + H₂O(l) → 2NaOH(aq)

•Anodising: Process of forming a thick oxide layer of aluminium that makes it resistant to further corrosion.

1. Reaction with water:

• All metals do not react with water. Those which react form metal oxide and hydrogen gas.

Metal oxides that are soluble in water further form metal hydroxide.

Metal + Water → Metal oxide + Hydrogen

Metal oxide + Water → Metal hydroxide

• Metals like sodium & potassium react with cold water vigorously; metals like magnesium react with hot water. Iron, zinc reacts with steam while lead, silver and gold do not react with water at all.

2K(s) + 2H₂O(l) → 2KOH(aq) + H₂(g) + heat energy

Ca(s) + 2H₂O(l) → Ca(OH)₂(aq) + H₂(g)

3Fe(s) + 4H₂O(g) → Fe₃O₄(s) + 4H₂(g)

1. Reaction with Dilute Acid:

• Most metals react with acids to give a salt and hydrogen gas.

Metal + Dilute acid → Salt + Hydrogen

• Hydrogen gas is not evolved when a metal reacts with nitric acid. It’s a strong oxidizing agent and oxidizes hydrogen produced to water and itself gets reduced to any of the nitrogen oxides (N₂O, NO, NO₂). But magnesium (Mg) and manganese (Mn) react with very dilute HNO₃ to evolve H₂ gas.

• Aqua Regia:

• Freshly prepared mixture of concentrated hydrochloric acid and concentrated nitric acid in the ratio of 3:1.

• Is a highly corrosive, fuming liquid and one of the few reagents able to dissolve gold and platinum.

• Reactivity of metals / Reactivity Series:

Figure 1: Activity Series : Relative reactivities of metals

1. Reaction of metals with metal salts:

• Reactive metals can displace less reactive metals from their compounds in solution or molten form.

How do metals and non-metals react:

•  The compounds formed by the transfer of electrons from a metal to a non-metal are known as ionic or electrovalent compounds.

•  Properties of ionic compound:

1. Physical Nature: Solid and hard due to strong inter-ionic force of attraction; generally brittle.

2. Melting and boiling points: High melting and boiling points since a considerable force is required to break the strong inter-ionic attraction.

3. Solubility: Generally soluble in water but insoluble in solvents such as kerosene, petrol, etc.

4. Conduction of electricity:

• Conducts electricity through solution due to movement of charged particles (ions).

• As movement of ions is not possible in solid state, due to rigid structure, do not conduct electricity.

• In molten state this movement is overcome due to heat and thus conducts electricity. Occurrence of Metals:

• Mineral: The elements or compounds, which occur naturally in the earth’s crust.

• Ore: Mineral that contains high percentage of metal that can be extracted profitably from it.

• Every ore is a mineral but every mineral is not an ore.

Obtaining metal from ore:

• Different techniques are to be used for obtaining the metals based on their reactivity.

1. Enrichment of ore:

• Ores mined from earth contain large amount of impurities such as sand, soil, etc. called gangue.

• Prior to the extraction of metal, based on the differences between the physical or chemical properties of gangue and the ore, different processes are used to remove gangue.

• Removal of gangue from ore is called enrichment of ore / concentration of ore.

Extraction of Metal:

1. Extraction of metals low in the Activity Series:

• These metals are generally very unreactive.

• Cinnabar (Mercuric sulphide, HgS) is the ore of Hg. When it is heated in air, it is first converted into mercuric oxide (HgO)

•  Mercuric oxides can be reduced to metals by heating alone.

For e.g. 2HgS(s) + 3O₂ (g) + Heat → 2HgO(s) + 2SO₂ (g) (Roasting)

            2HgO(s) + Heat → 2Hg+O₂

2.Extraction of Metals in the middle of the Activity Series:

The ores of these metals usually exist as sulphides and carbonates. It’s easy to obtain a metal from its oxide compared to its sulphide and carbonate. Therefore ,prior to reduction ,the
metal sulphides and carbonates can be converted into metal oxides by roasting and calcination.

• Roasting is a process of converting sulphide ores into oxides by heating strongly in the presence of excess air.

2ZnS(s) + 3O₂ (g) → 2ZnO(s) + 2SO₂ (g)

•Calcination is a process of converting carbonate ores into oxides by heating strongly in limited air.

ZnCO₃ (s) →ZnO(s) + CO₂ (g)

• Metal oxides are then reduced to corresponding metals using suitable reducing reagents such as coke.

• ZnO +C→ Zn +CO

• Besides using carbon(coke) to reduce metal oxides to metals ,sometimes displacement reactions can also be used. The highly reactive metals such as sodium ,calcium, , aluminium, etc. are used as reducing agents.

• These displacement reactions are highly exothermic; hence metals are produced in molten state.

•Thermit reaction: Reaction of iron oxide with aluminium used to join railway tracks or cracked machine parts.

   Fe₂O₃(s) + 2Al(s) → 2Fe(l) + Al₂O₃(s) + Heat

 

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