Solution-Class-10-CBSE-NCERT-Science-Chapter-3-Metals and Non-Metals

(i) Metal that exists in liquid state at room temperature → Mercury

(ii) Metal that can be easily cut with a knife → Sodium

(iii) Metal that is the best conductor of heat → Silver

(iv) Metals that are poor conductors of heat → Mercury and lead

Malleable: Substances that can be beaten into thin sheets are called malleable. Examples : Metals like Ag (silver), Au (gold) etc.

Ductile: Substances that can be drawn into thin wires are called ductile. Examples : Ag (silver), Au (gold) etc.

• Mineral : Most of the elements occur in nature as in combined state as minerals. The chemical composition of minerals is fixed.
• Ore: Minerals from which metals can be extracted profitably are known as ores.
• Gangue : The impurities (sand, silt, soil, gravel, etc.) present in the ore are called gangue.

(i) As per reactivity series, Iron is most reactive metal among Iron, Silver and Copper. Since B can displace Iron from its sulphate, so B is the most reactive metal

(ii) B will displace Cu from CuSO₄ solution because B is more reactive than copper.

(iii) The order of reactivity is B > A > C > D.

Hydrogen gas is produced when dilute hydrochloric acid is added to a reactive metal.

The chemical reaction when iron reacts with dil. H₂SO₄ is as follows

Zinc being more reactive than iron displaces iron from iron (II) sulphate solution. As the result, the green colour of the solution fades and iron metal gets deposited.

The chemical reaction when iron reacts with dil. H₂SO₄ is as follows.

(i) The electron dot structures of sodium (Na), oxygen (O) and magnesium (Mg) are tabulated below.

(ii) Ionic bond is formed in Na₂O and MgO.

(iii) (a) Na²O has Na⁺ and O²⁻ ions.

(b) MgO has Mg²⁺ and O²⁻ ions.

• In ionic compounds, strong electrostatic forces of attraction are present between the oppositely charged ions.
• When these compounds are heated, a lot of heat energy is required to break these strong electrostatic forces of attraction during melting.
• Therefore, ionic compounds have high melting and boiling points.

(i) Mineral : The naturally occurring elements or compounds of metals present in the earth's crust are called minerals.

(ii) Ore : Ores are those minerals from which a particular metal can be extracted profitably by using certain process.

(iii) Gangue : The undesirable impurities present in the ore are called gangue or matrix.

The metals at the bottom of the reactivity series are mostly found in free state. Examples: gold, silver, and platinum.

Metal is obtained from its oxide by reduction. The reduction can be done either by heating with carbon (coke) or by using highly reactive metals such as sodium, calcium, aluminium etc.

e.g. ZnO(s)      +    C(s)  → Zn(s) + CO(g)

      Zinc oxide              Coke       Zinc          Carbon monoxide

This reaction is highly exothermic. The heat produced is so large that metal is produced in the molten state.

• As the order of the reactivity of zinc, magnesium and copper is Mg > Zn > Cu.
• Thus, zinc will react with copper oxide to displace copper.
• Magnesium will also displace zinc from zinc oxide and copper from copper oxide. Copper, being least reactive will not react with any of the given oxides.

Metals present at the bottom of the reactivity series do not corrode easily, e.g. gold, silver, platinum etc.

• An alloy is a homogeneous mixture of two or more metals or a metal and a non-metal.
• It is prepared by mixing the metals in molten form and then cooling the mixture.
• The electrical conductivity and melting point of an alloy is less than that of pure metals.
• For example, steel is an alloy of iron and carbon.

(d) AgNO₃ solution will give displacement reaction with copper (Cu) because copper is placed above silver in the activity series, i.e. copper is more reactive than silver.

2AgNO₃(aq) +  Cu(s)  →  Cu(NO₃)₂(aq)  +  2Ag(s)

(c) Applying a coating of zinc will prevent an iron frying pan from rusting.

(a) Calcium : The compound is likely to be calcium (Ca) because it combines with oxygen to give CaO (calcium oxide) with very high melting point. Calcium oxide dissolves in water to form calcium hydroxide.

2Ca(s) + O₂(g) → 2CaO(s)

CaO(s) + H₂O(l) → Ca(OH)₂(aq)

(c) zinc is more reactive than tin :

Food cans are not coated with zinc because being more reactive than tin, zinc can react with organic acids present in the food.

(a) There are some ways by which we can distinguish between metals and non-metals as follows.

• Take the given samples of metals and non-metals; and strike them with the hammer. If it converts into a sheet, it is a metal and if not, it is non-metal. As metals are malleable, while non-metals are not.
• If it produces sound when struck with the hammer, it is a metal. But if it does not produce a sound, it is non-metal.
• Now arranging the given objects to form an electric circuit. Insert any one sample between clips A and B. If the bulb glows, it is a metal (good conductor of electricity). If the bulb does not glow, it is a non-metal.

(b) From the above tests, it is clear that metals are generally malleable, sonorous and good conductors of electricity, while non-metals are generally non-malleable/brittle, non-sonorous and poor conductors of electricity.

The metallic oxides which show the properties of acids as well as bases are called amphoteric oxides. It means that they react with both bases and acids to form salt and water. e.g. ZnO and Al₂O₃.

Zinc and magnesium displace H₂ from dilute acids while copper and silver do not.

• Anode (positively charged) Block of the impure metal M.
• Cathode (negatively charged) Strip of the pure metal M.
• Electrolyte Aqueous solution of a salt of the metal M.

(a)

• No change in colour will take place in case of dry blue litmus paper.
• The moist blue litmus paper will change its colour to red because sulphur is non-metal and so, its oxides are acidic in nature.

(b)

S(s) + O₂(g) → SO₂(g)

SO₂(g) + H₂O(l) → H₂SO₃(aq)

Here are some ways to keep iron from rusting:
(i) Painting or greasing the surface of iron can keep it from rusting by preventing direct contact with air.
(ii) The iron surface is galvanized, which coats it with zinc. Zinc is more reactive than iron, hence it will rust instead of iron.

Non-metals form acidic oxides, i.e. their aqueous solution turns blue litmus solution red.

(a) Platinum, gold and silver are non-reactive and give shining surface.

(b) Sodium, potassium and lithium are very reactive and catch fire when exposed to air.

(c) Aluminium forms a non-reactive layer of aluminium oxide on its surface.

(d) It is easier to reduce oxides into metal.

• Copper vessels get a green deposit of copper carbonate. This layer being insoluble in water, cannot be cleaned with water alone. But, it is soluble in acids.
• Lemon containing citric acid, tamarind containing tartaric acid or any other sour substance containing acid can be effective in cleaning the vessels. As these acids neutralises the basic copper carbonate and dissolves the layer.
• Hence, surface of copper vessels are cleaned with lemon or tamarind juice to give its characteristics lustre.

The man used aqua-regia, a mixture of conc. HCl and conc. HNO₃ in the ratio of 3 : 1. This is the only solution, that can dissolve gold. As the gold from the bangles was dissolved in aqua-regia, their weight was reduced drastically.

Iron (or steel) is more reactive than copper. Iron in contact with steam form Fe₃O₄.

3Fe(s) + 4H₂O(g) → Fe₃O₄(s) + 4H₂(g)

So, the body of tank is made of copper but not steel as copper does not react with water.