Metals and Non-metals Class 10 Science

20 Questions | 95 Marks

(a) Explain the process of anodising aluminium. 3marks(b) Why is anodising beneficial for aluminium? [2 marks]

A student observed that iron nails rusted in test tube A, but not in test tubes B and C. Test tube A contained water and air. Test tube B contained boiled distilled water with oil floating on top. Test tube C contained anhydrous calcium chloride.(a) Which test tube provided the conditions for rusting? [1 mark](b) Explain why rusting did not occur in test tubes B and C. 2marks

Explain the term 'amphoteric oxide' with suitable examples. 2marks

Observe the following reaction:

Z n S (s) + O_{2} (g) \overset{H e a t}{\to} Z n O (s) + S O_{2} (g)

(a) Identify the process shown in the equation. [1 mark] (b) What is the purpose of this process in the extraction of metals? [1 mark] (c) Name one other process used to convert carbonate ores to oxides. [1 mark]

When a metal X is heated with sulphur, it forms a compound Y. Compound Y is a solid and has a high melting point. It is insoluble in petrol but soluble in water. When the solution of Y is heated, it conducts electricity. (a) Identify the type of compound Y. [1 mark] (b) What can you conclude about metal X? [1 mark] (c) Give a reason why the solution of Y conducts electricity. 1mark

The reactivity series of some metals is given as: K > Na > Ca > Mg > Al > Zn > Fe > Pb > [H] > Cu > Hg > Ag > Au. (a) Which metal from the series will displace iron from iron(III) chloride solution? [1 mark] (b) Which metal from the series will not displace copper from copper(II) sulphate solution? [1 mark] (c) Which metal from the series is likely to be found in the free state? 1mark

(a) Name the process used to protect iron from rusting by coating it with a thin layer of zinc. [1 mark] (b) Why does the galvanised article remain protected even if the zinc coating is broken? 2marks

A student performs an experiment to study the reaction of metals with dilute hydrochloric acid and observes that while magnesium reacts vigorously, copper does not react at all. (a) Arrange magnesium, copper, and hydrogen in order of their reactivity. [1 mark] (b) Write the balanced chemical equation for the reaction between magnesium and dilute hydrochloric acid. 1mark

Describe the process of electrolytic refining of copper, mentioning the role of anode, cathode, and electrolyte. 3marks

Explain the formation of ionic compounds using the examples of sodium (atomic number 11) and chlorine (atomic number 17). Show the electron transfer and the resulting ions. 3marks

Name two metals that are found in nature as oxides. Give one reason why metals are often found as oxides in nature. 2marks

Define the terms 'mineral' and 'ore'. Give an example of a mineral that is an ore. 2marks

Explain with an activity why metals are generally good conductors of heat. 3marks

(a) What are alloys? [1 mark] (b) Brass is an alloy of copper and zinc. Bronze is an alloy of copper and tin. Explain why brass and bronze are not good conductors of electricity, whereas copper is used for making electrical circuits. 2marks

(a) Why is sodium kept immersed in kerosene oil? [1 mark] (b) Write the balanced chemical equation for the reaction of sodium with water. 1mark

A student observes that pure gold is very soft and not suitable for making jewellery. (a) What is done to make gold hard enough for jewellery? [1 mark] (b) What is the typical composition of 22 carat gold used in India? 1mark

You are given samples of four metals A, B, C, and D. When these metals are added to solutions of iron(II) sulphate, copper(II) sulphate, and silver nitrate, the following results are observed:

Metal	Iron(II) Sulphate	Copper(II) Sulphate	Silver Nitrate
A	No reaction	Displacement	Displacement
B	Displacement	Displacement	Displacement
C	No reaction	No reaction	Displacement
D	No reaction	No reaction	No reaction
(a) Which is the most reactive metal among A, B, C, and D? [1 mark]
(b) What would happen if metal A is added to a solution of copper(II) sulphate? [1 mark]
(c) Arrange the metals A, B, C, and D in the order of decreasing reactivity. [2 marks]

Give reasons: (a) Platinum, gold and silver are used to make jewellery. [1 mark] (b) Aluminium utensils are often coated with a thin layer of oxide. 2marks

(a) What are the two conditions necessary for the rusting of iron? [1 mark] (b) Explain why the rusting of iron is faster in coastal areas than in deserts. 2marks

Write the balanced chemical equations for the following reactions: (a) Reaction of iron with steam. [1 mark] (b) Reaction of aluminium with dilute hydrochloric acid. [1 mark] (c) Electrolysis of molten magnesium chloride. 2marks

Answers

(a) Anodising is an electrochemical process used to increase the thickness of the natural oxide layer on the surface of aluminium articles. In this process, 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 form a thicker protective oxide layer, which can also be dyed. [3 marks] (b) The thick oxide layer formed during anodising makes the aluminium resistant to further corrosion and also gives it an attractive finish when dyed. 2marks

(a) Test tube A. [1 mark] (b) In test tube B, the boiled distilled water had oil floating on it, preventing dissolved oxygen from entering the water, thus preventing rusting. In test tube C, the anhydrous calcium chloride absorbed any moisture from the air, making the air dry, which is essential for rusting. 2marks

Amphoteric oxides are those metal oxides which exhibit both acidic as well as basic properties. They react with both acids and bases to produce salt and water. Examples: Aluminium oxide (

A l_{2} O_{3}

) and Zinc oxide (

Z n O

). 2marks

(a) Roasting. [1 mark] (b) This process is used to convert sulphide ores into metal oxides, which can then be easily reduced to metals. [1 mark] (c) Calcination. 1mark

(a) Ionic compound. [1 mark] (b) Metal X is likely a reactive metal that forms positive ions. [1 mark] (c) The solution of Y conducts electricity because it contains mobile, charged ions that can move towards the electrodes when an electric current is passed. 1mark

(a) Metals above hydrogen in the activity series can displace hydrogen. Metals above iron in the series can displace iron. Therefore, K, Na, Ca, Mg, Al, Zn would displace iron. From the given series, any metal above Iron (Fe) would displace iron. For example, Aluminium (Al) would displace iron. [1 mark] (b) Metals below copper in the activity series will not displace copper. From the given series, Hg, Ag, Au will not displace copper. [1 mark] (c) Metals at the top of the activity series are very reactive and are found in combined states. Metals at the bottom of the activity series are least reactive and are often found in the free state. Thus, Gold (Au) is likely to be found in the free state. 1mark

(a) Galvanisation. [1 mark] (b) Zinc is more reactive than iron. Even if the zinc coating is broken, the zinc will preferentially corrode (act as a sacrificial anode) and protect the iron from rusting. 2marks

(a) Reactivity order: Magnesium > Hydrogen > Copper. [1 mark] (b)

M g (s) + 2 H C l (a q) \to M g C l_{2} (a q) + H_{2} (g)

[1 mark]

In the electrolytic refining of copper: Anode: A thick strip of impure copper. Cathode: A thin strip of pure copper. Electrolyte: An acidified solution of copper sulphate (

C u S O_{4}

). When electric current is passed, pure copper from the anode dissolves into the electrolyte as

C u^{2 +}

ions. An equivalent amount of pure copper ions from the electrolyte are deposited as pure copper on the cathode. Soluble impurities go into the solution, and insoluble impurities (anode mud) settle down at the bottom of the anode. 3marks

Sodium (Na) has atomic number 11, with electronic configuration 2, 8, 1. It readily loses its outermost electron to form a sodium cation (

N a^{+}

) with a stable octet configuration (2, 8).

N a \to N a^{+} + e^{-}

Chlorine (Cl) has atomic number 17, with electronic configuration 2, 8, 7. It needs one electron to complete its outermost shell. It gains the electron lost by sodium to form a chloride anion ( $C l^{-}$ ) with a stable octet configuration (2, 8, 8).

C l + e^{-} \to C l^{-}

The oppositely charged ions ( $N a^{+}$ and $C l^{-}$ ) attract each other strongly, forming an ionic compound, sodium chloride (NaCl). [3 marks]

Two metals that are found in nature as oxides are Aluminium (Al) and Iron (Fe) (in their respective ores like bauxite and hematite). Reason: Oxygen is a very reactive element and is abundant in the Earth's crust. Therefore, many metals react with oxygen to form metal oxides. 2marks

Mineral: A substance in which elements or compounds occur naturally in the Earth's crust. Ore: A mineral from which a metal can be extracted profitably and easily. Example: Bauxite is a mineral and also an ore of aluminium. 2marks

Activity: Take a metal rod (e.g., copper or aluminium). Clamp a metal wire (e.g., copper wire) horizontally on a stand. Fix pins to the free end of the wire using wax. Heat the clamped end of the wire with a spirit lamp. After some time, the heat travels along the wire, the wax melts, and the pins fall one by one. This demonstrates that metals are good conductors of heat, as they allow heat to pass through them easily. 3marks

(a) An alloy is a homogeneous mixture of two or more metals, or a metal and a non-metal. [1 mark] (b) Alloys like brass and bronze have different constituent metals (copper, zinc, tin) which possess different electrical properties compared to pure copper. While copper itself is an excellent conductor, the presence of other metals in the alloy affects the free movement of electrons, making them poorer conductors. Copper's high conductivity and relative ductility make it suitable for electrical circuits. 2marks

(a) Sodium is a highly reactive metal. It reacts vigorously with oxygen and moisture present in the air, leading to fire. To prevent this, it is stored under kerosene oil, which prevents it from coming into contact with air and moisture. [1 mark] (b)

2 N a (s) + 2 H_{2} O (l) \to 2 N a O H (a q) + H_{2} (g) + heat energy

[1 mark]

(a) Pure gold is alloyed with small amounts of other metals like silver or copper to make it hard enough for jewellery. [1 mark] (b) 22 carat gold means that out of 24 parts, 22 parts are pure gold and the remaining 2 parts are usually copper or silver. 1mark

(a) Metal B, as it displaces all the other metals from their sulphate solutions, indicating it is the most reactive. [1 mark] (b) Metal A is more reactive than copper but less reactive than iron and silver (as it displaces silver but not iron, and displaces copper but not iron). If metal A is added to copper(II) sulphate solution, no reaction would be observed because A is less reactive than copper. [1 mark] (c) B > A > C > D. 2marks

(a) Platinum, gold, and silver are unreactive (noble metals). They do not corrode or tarnish easily when exposed to air and moisture, which makes them ideal for making long-lasting and beautiful jewellery. [1 mark] (b) Aluminium forms a thin, protective layer of aluminium oxide (

A l_{2} O_{3}

) when exposed to air. This layer prevents further reaction and corrosion. In utensils, this oxide layer helps in resisting corrosion and making them durable for cooking. 2marks

(a) The two necessary conditions for the rusting of iron are: (i) Presence of oxygen (from the air). (ii) Presence of water or moisture. [1 mark] (b) Coastal areas have a higher concentration of moisture and dissolved salts (like sodium chloride) in the air. Dissolved salts act as an electrolyte and increase the rate of rusting, making it faster than in deserts where the air is generally dry. 2marks

(a)

3 F e (s) + 4 H_{2} O (g) \overset{S t e a m}{\to} F e_{3} O_{4} (s) + 4 H_{2} (g)

[1 mark] (b)

2 A l (s) + 6 H C l (a q) \to 2 A l C l_{3} (a q) + 3 H_{2} (g)

[1 mark] (c) At cathode:

M g^{2 +} + 2 e^{-} \to M g (l)

At anode:

2 C l^{-} \to C l_{2} (g) + 2 e^{-}

[2 marks]

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Metals and Non-metals — Important Questions

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