Class 10 Metal and Non MetalsChapter 03 NCERT Activity Solutions

X Class 10 NCERT Activity Explanation Class 10 Metals and Non Metals

Activity 3.1 Page No. 37

Take samples of iron, copper, aluminium and magnesium. Note the appearance of each sample.
They have a shining surface.
Clean the surface of each sample by rubbing them with sand paper and note their appearance again. They become more shiny. => Freshly cut Metal have shiny surface

Activity 3.2 Page No. 37

Take small pieces of iron, copper, aluminium, and magnesium. Try to cut these metals with a sharp knife and note your observations.
They are very hard to cut.
Hold a piece of sodium metal with a pair of tongs and try to cut it with a knife.
Sodium can be cut easily with knife.
Hence K and Na are soft metal cut with knife

Activity 3.3 Page No. 38

Take pieces of iron, zinc, lead and copper try to strike it four or five times with a hammer.
These metals are beaten into thin sheet on hammering. This property of metal is called malleability and metals are called malleable.

Activity 3.4 Page No. 38

Take some metals such as iron, copper, aluminium, lead, etc.
Which of the above metals are also available in the form of wires?
Iron, copper and aluminium are metals which are drawn into wire. This properties of metal is called ductility and metals are called ductile.

Activity 3.5 Page No. 39

Take an aluminium or copper wire. Clamp this wire on a stand, as shown in Figure.
Fix a pin to the free end of the wire using wax and Heat the wire with a spirit lamp
What do you observe after some time?
After some time the wax melts and the pin falls down. Does the metal wire melt?
Metal Wire does not melt . Hence metals are good conductor of Heat.

Activity 3.6 Page No 39

Set up an electric circuit and Place the metal to be tested in the circuit between terminals A and B
Does the bulb glow? What does this indicate?
Yes, the bulb glow. This indicate that metal are a conductor of electricity

Activity 3.7
Collect samples of carbon (coal or graphite), sulphur and iodine.

Element	Surface	Hardness	Malleability	Ductility	coductivity	Sonority
Carbon	rough	moderate	No	No	No	No
Sulphur	rough	not hard	No	No	No	No
Iodine	shiny	not hard	No	No	No	No

Activity 3.8 Page No 49
Take a magnesium ribbon and some sulphur powder.
Burn the magnesium ribbon. Collect the ashes formed and dissolve them in water.

Test the resultant solution with both red and blue litmus paper.
2Mg + O2 = 2MgO ; MgO + H2O = Mg(OH) 2

Magnesium oxide is basic as red litmus changes into blue
Now burn sulphur powder. Place a test tube over the burning sulphur to collect the fumes produced. Add some water to the above test tube and shake.

Oxide of sulphur changes blue litmus into red so it is Acidic.
S + O2 = SO2 ; SO2 + H2O = H2SO4
Hence metal oxides are basic and Acidic oxides are acidic.

Physical properties observed are:

· Gallium and caesium have very low melting points and they will melt on your palm.
· Iodine and Graphite are lustrous non-metal.
· Diamond, an allotrope of carbon, is the hardest natural substance known and has a very high melting and boiling point.
· Graphite, another allotrope of carbon, is a conductor of electricity.
· Alkali metals (lithium, sodium, potassium) are so soft that they can be cut with a knife. They have low densities and low melting points.

Activity 3.9

Try burning different metals over a flame
Which metals burn easily? Magnesium
What flame colour did you observe when the metal burnt? Blue flame
How does the metal surface appear after burning? dazzling white.
Arrange the metals in the decreasing order of their reactivity towards oxygen.

Answer. Na > Mg > Al > Zn > Fe > Pb > Cu
Are the products soluble in water?

Oxides of Alumium,Copper, Iron, Lead, Mg, Zn are not Soluble.
Soudium Oxide is soluble in water
Na2O(s) + H2O(l) → 2NaOH(aq)
K2O(s) + H2O(l) → 2KOH(aq)

when copper is heated in air, it combines with oxygen to form copper(II) oxide, a black oxide.
2Cu + O2 → 2CuO(Black)

Similarly, aluminium forms aluminium oxide. 4Al + 3O2 → 2Al2O3

Amphoteric oxides : aluminium oxide, zinc oxide, etc., show both acidic as well as basic behaviour. Such metal oxides which react with both acids as well as bases to produce salts and water are known as amphoteric oxides.

Al2O3 + 6HCl → 2AlCl3 + 3H2O ; Al2O3 + 2NaOH → 2NaAlO2 + H2O

Note:
Metals such as potassium and sodium react so vigorously that they catch fire if kept in the open. Hence, to protect them and to prevent accidental fires, they are kept immersed in kerosene oil.
At ordinary temperature, the surfaces of metals such as magnesium, aluminium, zinc, lead, etc., are covered with a thin layer of oxide. The protective oxide layer prevents the metal from further oxidation. Thus rusting is beneficial .
During anodising, a clean aluminium article is made the anode and is electrolysed with dilute sulphuric acid. The oxygen gas evolved at the anode reacts with aluminium to make a thicker protective oxide layer which make it attractive and corrosion resistant.

Activity 3.10

Arrange them in the increasing order of their reactivity with cold water.
Sodium, Potassium and Calcium are the metals which reacted with cold water to form metal oxide and release hydrogen gas.
This reaction is so violent and exothermic that the evolved hydrogen immediately catches fire. So they are stored in wax or kerosene.
Their increasing order of reactivity with cold water is => Calcium < Potassium < Sodium
Sodium and Potassium produce fire on water
2K(s) + 2H2O(l) → 2KOH(aq) + H2(g) + heat energy
2Na(s) + 2H2O(l) → 2NaOH(aq) + H2(g) + heat energy
Does any metal start floating after some time?
Calcium start floating because the bubbles of hydrogen gas formed stick to the surface of the metal.
Ca(s) + 2H2O(l) → Ca(OH)2(aq) + H2(g)
Magnesium reacts with hot water to form magnesium hydroxide and hydrogen. It also starts floating due to the bubbles of hydrogen gas sticking to its surface.
Metals like aluminium, iron and zinc react only with steam to form the metal oxide and hydrogen.
2Al(s) + 3H2O(g) → Al2O3(s) + 3H2(g)
3Fe(s) + 4H2O(g) → Fe3O4(s) + 4H2(g)
Metals such as lead, copper, silver and gold do Copper, Lead, Silver and Gold do not react with water or steam at all.

Activity 3.11

Put the metals except sodium and potassium in test tubes containing dilute hydrochloric acid.
Suspend thermometers in the test tubes, so that their bulbs are dipped in the acid.
Magnesium, aluminium, zinc and iron with dilute hydrochloric acid to form salt and release Hydrogen gas.

 
Mg > Al > Zn > Fe.

In the case of copper, no bubbles were seen and the temperature also remained unchanged. This shows that copper does
Hydrogen gas is not evolved when a metal reacts with nitric acid.
It is because HNO3 is a strong oxidising agent. It oxidises the H2 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 : it is a mixture of concentrated hydrochloric acid and concentrated nitric acid in the ratio of 3:1. It can dissolve gold and platinum.

Activity 3.12

Put the copper wire in a solution of iron sulphate in test tube A and the iron nail in a solution of copper sulphate taken in test tubes B
In which test tube did you find that a reaction has occurred? Test tube B
On what basis can you say that a reaction has actually taken place?
Fe is more reaction than Cu so displacement rection takes place.
The reactivity series : it is a list of metals arranged in the order of their decreasing activities.

Activity 3.13

Sodium chloride, potassium iodide, barium chloride salt are ionic compound formed by the transfer of electrons from a metal to a non-metal . They are known as ionic compounds or electrovalent compounds.

1. Ionic compounds are solids and but brittle because of the strong force of attraction between the positive and negative ions.

2. Ionic compounds have high melting and boiling points . This is because a considerable amount of energy is required to break the strong inter-ionic attraction.

3. They are generally soluble in water and insoluble in solvents such as kerosene, petrol, etc.

4. They are good conductor as they have ions.

Activity 3.14

Take three test tubes A,B, and C and place clean iron nails in each of them
· Pour water in test tube A and cork it.
· Pour boiled distilled water in test tube B, add about 1 mL of oil and cork it.
· Put some anhydrous calcium chloride in test tube C and cork it.
Leave these test tube for some days and then observe.
Iron nails rust in test tube A, but they do not rust in test tubes B and C.
Reason:
In test tube A iron get both air and water.
Fe + H2O + O2 à Fe2O3.H20
In test tube B , The oil will float on water and prevent the air from dissolving in the water and prevent rusting iron.
In Test tube C, Anhydrous calcium chloride will absorb the moisture and prevent rusting iron.
Thus moisture and air essential for rusting.
Silver articles become black after some time when exposed to air. This is because it reacts with sulphur in the air to form a coating of silver sulphide. Ag + S à Ags
Copper reacts with moist carbon dioxide in the air and slowly loses its shiny brown surface and gains a green coat of basic copper carbonate. Cu + CO2 + H2O à CuCO3.Cu(OH)3
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