Class 10 Science Notes - METALS AND NON-METALS

v  Elements are classified broadly into two categories on the basis of properties:

v  Metals: Iron, Zinc, Copper, Aluminium etc.

v  Non- metals: Chlorine, Nitrogen, Hydrogen, Oxygen, Sulphur etc.

v  Apart from metals and non-metals some elements show properties of both metals and non-metals,

Example: Silicon, Arsenic, Germanium.They are called metalloids.

Comparison of physical and chemical properties of metals and non – metals:-

Sl. No.	Property	Metals	Non-Metals
1	Physical State	Metals are solid at room temperature. Except mercury and gallium.	Non-metals generally exist as solids and gases, except Bromine.
2	Melting and boiling points	Metals generally have high m.pt and b.pt except gallium and caesium.	Non-metals have low m.pt and b.pt except diamond and graphite.
3	Density	Generally high.	Generally low.
4	Malleability and Ductility	Malleable and ductile.	Neither malleable nor ductile.
5	Electrical and thermal conductivity	Good conductors of heat and electricity.	Generally poor conductors of heat and electricity except graphite.
6	Luster	Poses shining lustre.	Do not have lustre except iodine.
7	Sonorous sound	Give sonorous sound when struck.	Does not give sonorous sound.
8	Hardness	Generally hard except Na, K	Solid non-metals are generally soft except diamond.

Comparison of Chemical Properties of Metals and Non-metals:-

1	Reaction with Oxygen	Metal + Oxygen® Metal oxide 4Na(s) + O2(g) ® 2Na2O(s) 4Al(s) + 3O2(g) ® 2Al2O3 Metals form basic oxides.           Zn and Al form amphoteric oxides (they show the properties of both acidic and basic oxides)                                   Most of the metal oxides are insoluble in water. Some of them dissolve to form Alkali                                                     Na2O(s) + H2O(l) ® 2NaOH(aq)	Non-metal + Oxygen ® Non-metal oxide                                            C + O2® CO2 S + O2® SO2 Non-metals form acidic oxides.                                              CO and H2O are neutral oxides(they are neither acidic nor basic in nature). Non-metal oxides are soluble in water                                             They dissolve in water to form acid. example SO2 +H2O ® H2SO3
2	Reaction with water	Metals react with water to form metal oxides or metal hydroxide and H2 gas is released.                           2Na(s) + 2H2O(l) ® 2NaOH +                                       H2(g) + heat	Non-metals do not react with water, steam to evolve hydrogen gas. Because Non-metals cannot give electrons to hydrogen in water so that it can be released as H2 gas.
3	Reaction with dilute Acids	Metal + Acid ® Metal salt + Hydrogen                                                            Mg(s)+2HCl(aq)àMgCl2(aq)+H2(g)     2Na(s)+H2SO4àNa2SO4(aq) +H2(g)Metal+HNO3àH2 gas is not displaced.                                        Reason- HNO3 is strong oxidizing agent. It oxidises hydrogen to water.	Non-metals do not react with acids to release H2 gas                   Reason- Non-metals cannot loose electrons and give it to Hydrogen ions of acids so that the gas is released.
4	Reaction with salt solutions	When metals react with salt solution, more reactive metal will displace a less reactive metal from its salt solution.            CuSO4(aq)+Zn(s)àZnSO4(aq)+Cu(s)	When non-metals react with salt solution, more reactive non-metal will displace a less reactive non-metal from its salt solution.                                           2NaBr(aq)+Cl2(g)à2NaCl(aq)+Br2(aq)
5	Reaction with Chlorine	Metal + Chlorine à Metal Chloride                                            ionic bond is formed. Therefore Ionic compound is obtained.                   2Na + Cl2à 2NaCl	Non-metal + Chlorine à Non-metal Chloride. Covalent bond is formed. Therefore covalent compound is obtained.                     H2(g) + Cl2à 2HCl
6	Reaction with Hydrogen	Metals react with hydrogen to form metal hydride. This reaction takes place only for most reactive metals.                     2Na(s) + H2(g) à 2NaH(s)	Non-metals react with hydrogen to form hydrides         H2(g) + S(l) à H2S(g)

Properties of ionic compounds 

1. Physical nature:solid and hard due to strong force of attraction.  (generally brittle)
2. Melting point and boiling point:have high M.P and B.P, as large amount of heat energy is required to break strong ionic attraction.
3. Solubility: soluble in water and insoluble in kerosene and pertrol.
4. Conduction of electricity:ionic compounds in solid state-----does not conduct electricity.

Reason—Ions can not move due to rigid solid structure. Ionic compounds conduct electricity in molten state.

Reason--  Ions can move freely since the electrostatic forces of attraction between the oppositely charged ions are overcome due to heat.

Occurrence of metals.

                                It occurs in Earths crust, sea-water

 

Ores

Minerals

                                                                             

Elements or compounds, occuring naturally                             Minerals that contain very high             percentage

                                                                                                                                                                                                 in the earth’s  crust                                                                     of a perticular metal and these metals can be

                                                                                                      extracted economically on a large scale.

                                                                                                       e.g Bouxite ore  → Aluminium

                                                                                                             Haematite    → Iron

Class 10 Notes - ACIDS, BASES AND SALTS

1)      Acids are sour in taste, turn blue litmus red, and dissolve in water to release H⁺ ions e.g. HCl, H₂SO₄, HNO₃ etc.

2)      Bases are bitter in taste, have soapy touch, turn red litmus blue and give hydroxide ions in solution.

e.g.  NaOH, KOH etc.

3) A salt is a compound which is formed by neutralization reaction between an acid and base.

             e.g. sodium chloride.

3)      Indicators – Indicators are substances which indicate the acidic or basic nature of the solution

by their colour change.

     The colour of some acid – base indicators in acidic and basic medium are given below

Sr. No.	INDICATORS	COLOUR IN ACIDIC MEDIUM	COLOUR IN BASIC MEDIUM
1	Litmus solution	Red	Blue
2	Methyl Orange	Pink	Orange
3	Phenolphthalein	Colourless	Pink
4	Methyl red	Yellow	Red

                            

5) Chemical properties of acids:

    i) Acids react with active metals to give hydrogen gas.

                     Zn + H₂SO₄àZnSO₄ + H₂

ii) Acids react with metal carbonate and metal hydrogen carbonate to give carbon dioxide.

                    NaHCO₃ +HCl àNaCl + H₂O + CO₂

  iii) Acids react with bases to give salt and water. This reaction is called as neutralization reaction.

                    NaOH + HCl à NaCl +H₂O

  iv) Acids react with metals oxides to give salt and water.

                   CuO + H₂SO₄ à CuSO₄ + H₂O

6) Chemical properties of Bases:

i) Reaction with Metals - Certain reactive metals such as Zinc, Aluminium, and Tin react with alkali solutions on heating and hydrogen gas is evolved.

                          2NaOH + Zn à  Na₂ZnO₂ +H₂

ii) Reaction with acids -Bases react with acids to form salt and water.

                           KOH +HCl à KCl +H₂O

iii) Reaction with Non -metallic oxides – These oxides are generally acidic in nature. They react with bases to form salt and water.

                           2NaOH + CO₂à Na₂CO₃ + H₂O

7) PH Scale: The concentration of hydrogen ion in solution is expressed in terms of pH. The pH of a solution is defined as the negative logarithm of hydrogen ion concentration in moles per liter.

                                       pH = - log [H⁺]

For water or neutral solutions, pH = 7 ; For acidic solutions, pH < 7;  For basic solutions, pH > 7

8) Some Important Chemical Compounds:

a)Common Salt (NaCl)

Sodium chloride is known as common salt. Its main source is sea water. It is also exists in the                                                form of rocks and is called rock salt.

Common salt is an important component of our food. It is also used for preparing sodium hydroxide, baking soda, washing soda etc.

b)Sodium Hydroxide or Caustic Soda (NaOH)

It is prepared by passing electricity through an aqueous solution of sodium chloride also known as brine.

           2NaCl (aq) + 2 H₂O (l) à 2NaOH (aq) + Cl₂ (g) + H₂ (g)

This process is known as chlor-alkali process.

Properties:

1. It is white translucent solid.

2. Crystals of sodium hydroxide are deliquescent.

3. It is readily soluble in water and gives strong alkaline solution.

c) Bleaching Powder (CaOCl₂)

Its chemical name is calcium oxychloride. It is prepared by passing chlorine gas through dry slaked lime.

                   Ca (OH) ₂ + Cl₂àCaOCl₂ + H₂O

Uses –

1. For bleaching cotton and linen in textile industry and wood pulp in paper industry

2. For disinfecting drinking water.

d) Baking Soda (NaHCO₃)

Chemical name is Sodium hydrogen carbonate.

It is prepared by passing CO₂ gas through brine solution saturated with ammonia.

                  NaCl + H₂O +CO₂ +NH₃à NH₄Cl + NaHCO₃

Properties:

1. It is white crystalline solid and sparingly soluble in water at room temperature.

2. On heating it decomposes to give sodium carbonate and carbon dioxide.

3. It reacts with acids to give carbon dioxide gas.

4. It aqueous solution is weak alkaline due to hydrolysis.

Uses:

1. It is used in soda – acid fire extinguisher.

2. It acts as mild antiseptic and antacid.

3. It is used as a component of baking powder. In addition to sodium hydrogen carbonate baking soda contains tartaric acid.

e) Washing Soda (Na₂CO₃.10 H₂O)

Chemical name is sodium carbonate decahydrate.

It is prepared by heating baking soda. Recrystallisation of sodium carbonate gives washing soda.

                     2NaHCO₃à Na₂CO₃ +H₂O +CO₂

                     Na₂CO₃ +10 H₂O  à Na₂CO₃. 10 H₂O

Uses:

1. It is used for removing permanent hardness of water.

2. It is used in glass, soap and paper industries.

3. It can be used as a cleaning agent for domestic purposes.     

f) Plaster of Paris (CaSO₄._1/2H₂O)

Its chemical name is calcium sulphate hemihydrates. It is obtained by heating Gypsum upto 373K.

CaSO₄.2H₂O à CaSO₄._1/2H₂O + 1_1/2H₂O

On treatment with water it is again converted into gypsum and sets as a hard mass.

CaSO₄._1/2H₂O+1_1/2H₂OàCaSO₄.2H₂O

Uses:-

1. It is used by doctors for setting fractured bones.
2. It is used for making statues, models and other decorative materials.