(i) Charcoal produces carbon dioxide on burning. This gas turns lime water milky and its solution turns blue litmus to red. Hence, it is acidic
(ii) \(\underset{Carbon}{C}+\underset{Oxygen}{O_2}⟶\underset{Carbon\ di\ oxide}{CO_2}\)

Physical properties of metals:
(i) Metals are good conductors of heat and electricity.
(ii) Metals are malleable and ductile.
(iii) They are lustrous and can be polished.
(iv) Generally they are solid at room temperature except mercury.
(v) Metals generally have high melting and boiling points.

Activity to test whether sulphur solution is acidic or basic in nature:
(i) Take a small amount of powdered sulphur in a deflagrating spoon and heat it.
(ii) As sulphur starts burning introduce it into a gas jar.
(iii) Cover the gas jar so that gas produced does not escape.
(iv) Remove spoon after some time, add a small quantity water.
(v) Shake it well. Sulphur solution is ready.
(vi) Test it with red and blue litmus papers.
(vii) It turns blue litmus paper red. Hence it is acidic in nature

(a) The copper objects lose their shine after sometime due to the formation of green coating of basic copper carbonate on its surface. When a copper object remains in damp air for a considerable time, then copper reacts slowly with the carbon dioxide, water and air, it acquires a dull appearance.
(b) Yes, copper vessel also gets rusted. The formation of this green coating on the surface of a copper object corrods it. The green material is a mixture of copper hydroxide, Cu (OH)₂ and copper carbonate (CuCO₃). The following is the reaction
\(2cu+\underbrace { H_{ 2 }O+CO_{ 2 }+O_{ 2 } }_{ Moistair } \rightarrow Cu(OH)_{ 2 }+CuCO_{ 3 }\)
(c) The values exhibited by Rakhi are awarness, helpful and knowledgeable.

(a) When charcoal is burnt, carbon dioxide gas is produced. This gas turns lime water into milky colour. The nature of the gas can be tested by using aqueous solution of carbon dioxide on moist red and blue litmus paper. No effect on red litmus but the solution turns blue litmus to red, so it is acidic in nature .
(b) Equations of all the reactions are given as below:
Carbon + Oxygen\(\rightarrow \) Carbon dioxide 
Carbon dioxide + Lime water \(\rightarrow \) Milky
Carbon dioxide + Water \(\rightarrow \)Carbonic acid
Carbonic acid + Blue litmus\(\rightarrow \) Red litmus

(i) No change in the colour of blue litmus.
(ii) The red litmus changes into blue colour.

Phosphorus is a very reactive non-metal. It catches fire if exposed to air. To prevent contact of phosphorus with atmospheric oxygen it is stored in water.

Iron and zinc neither reacts with cold water nor with hot water but reacts with steam to produce hydrogen gas.

Mercury metal is used for making thermometers.

Metals produce ringing sound, so they are called sonorous.

Precautions while handling the equipments containing mercury are as follows:
(i) Mercury, a liquid metal with high density, can corrode the skin if it drops over it. Hence, the vessel should be closed or tightly packed.
(ii) It should not be heated directly

The wasting of iron objects due to rusting causes a big loss to the country's economy, so it must be prevent by following methods:
(i) By painting : Paint is applied to the surface of an iron object, then air and moisture cannot come in contact of iron and hence no rusting occurs.
(ii) By applying grease or oil : Tools and machine parts made of iron and steel are smeared with grease or oil to prevent their rusting.
(iii) By galvanization : Galvanization is done by dipping an iron object in molten zinc metal. This thin layer of zinc metal on the surface of iron objects protects them from rusting.
(iv) By tin plating and chromium-plating : When a thin layer of tin metal is deposited on iron and steel objects by electroplating then the iron and steel objects are protected from rusting.
(v) By alloying it to make stainless steel: When iron is alloyed with chromium and nickel, stainless steel is obtained, which does not rust at all

a) Chemical properties of metals:
(i) Metals react with oxygen to produce oxides which are alkaline in nature. e.g.,
\(\underset{Magnesium}{Mg}+\underset{Oxygen}{O_2}⟶\underset{Magnesium\ oxide}{2MgO}\)
(ii) Metallic oxides produce bases by reacting with water differently
\(\underset{Sodium\ oxide}{Na_2O}+\underset{Water}{H_2O}⟶\underset{Sodium\ hydroxide}{2NaOH}\)
(iii) Metals react with acid to produce hydrogen gas
\(\underset{Hydrochloric\ acid}{2HCI}+\underset{Sodium}{2Na}⟶\underset{Sodium\ chloride}{2NaCl}+\underset{Hydrogen}{H_2}\)
(iv) More reactive metals displace the less reactive metals from their compounds in an aqueous solution 
\(\underset{Copper\ Sulpahte}{CuSO_4}+\underset{Zinc}{Zn}⟶\underset{Zinc\ Sulphate}{ZnSO_4}+\underset{Copper}{Cu}\)
(b) Chemical properties of Non-metals
(i) Non-metals react with oxygen to produce oxides which are acidic in nature
\(\underset{Sulphur}{S}+\underset{Oxygen}{O_2}⟶\underset{Sulphur\ dioxide}{SO_2}\)
\(\underset{Sulphur\ dioxide}{SO_2}+\underset{Water}{H_2O}⟶\underset{Sulphurous\ Acid}{H_2SO_3}\)
(ii) Non-metals do not react with water.
(iii) Non-metals do not show displacement reactions.

(a) Firstly, gold is highly malleable and ductile. Secondly, it is not attacked by the gases of air.
(b) We prefer copper wire because it is the better electrical conductor than aluminium. However, silver is the best electrical conductor but it is very expensive.
(c) Silver is the better conductor of heat than copper.
(d) Yes, they are harmful for us because they affect throat and lungs.