(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.

Acids: Acids are formed when non-metals react with oxygen and form non-metallic oxides. These oxides when dissolved in water, form acids, e.g.,
\(\underset{sulphur}{S}+\underset{Oxyhen}{O_2}⟶\underset{Sulphur\ dioxide}{SO_2}\) , \(\underset{Sulphur\ dioxide}{SO_2}+\underset{Water}{H_2O}⟶\underset{Sodium\ Hydroxide}{2NaOH}\) 

Important uses of non-metals:
(i) Non-metals are essential for our life as all living beings inhale oxygen and breath out carbon dioxide during breathing.
(ii) They are used in fertilizers to enhance the growth of plants.
(iii) Non-metal is used in the purple coloured solution that is applied on wounds as an antiseptic.
(iv)Non-metals are used in crackers.

When a more reactive element displaces a less reactive element or molecule from its salt, such reactions are called displacement reactions. These reactions can be well explained in metals. When in copper sulphate solution zinc granules are added, the blue colour of copper sulphate disappears and a powdery red mass of copper is deposited at the bottom of the beaker. The reaction can be represented as follows:
\(\underset{(Blue)}{CuSO_4}+Zn⟶\underset{(Colourless)}{ZnSO_4}+\underset{(Red)}{Cu}\)

(a) The container becomes porous when blue copper sulphate solution is kept into it because iron being more reactive displaces copper from copper sulphate solution and itself form green coloured ferrous sulphate.
(b) Qualities exhibited by Mohan are scientific knowledge, awareness and helpfulness.

In a chemical reaction, when a more reactive metal displaces the less reactive metal from its salt solution, it is called displacement reaction, e.g. zinc can displace copper from its copper sulphate solution as zinc is more reactive than copper. Less reactive metal cannot displace the more reactive metal from its salt solution, e.g. copper cannot displace zinc from its zinc sulphate solution as copper is less reactive than zinc.

Magnesium is found in plants in the form of ionic salts in chlorophyll. Due to its deficiency, plants are unable to produce enough chlorophyll and as a result, leaves develop yellowish colour.

Yes, iron piece will Change its shape as it is a metal. It increases in size and does not break. If a wood log is beaten, it does not Change its shape but it breaks into pieces.

Metals react with acids to produce salt and hydrogen gas which burns with a 'pop' sound. Non-metals do not react with acids. Copper does not react with dilute hydrochloric acid and dilute sulphuric acid but it reacts with hot and concentrated sulphuric acid, but no hydrogen gas is produced.

When a copper vessel is exposed to moist air for a long time, it acquires a dull green coating. The green substance is the mixture of copper hydroxide [Cu(OH)₂]and copper carbonate (CuCO₃).
\(2cu+\underbrace { H_{ 2 }O+CO_{ 2 }+O_{ 2 } }_{ Moistair } \rightarrow \underbrace { Cu(OH)_{ 2 }+CuCO_{ 3 } }_{ Green\quad coating​​​​​​​ } \)

(a) Copper does not react with dilute sulphuric acid, so no reaction will take place.
(b) When iron nails are placed in copper sulphate solution, displacement reaction takes place in which iron displaces copper as iron is more reactive than copper.
Copper sulphate+ Iron\(\rightarrow \) Iron sulphate +Copper
 (CuSO₄)               (Fe)     (FeSO₄)           (Cu3)

No, we cannot store lemon pickle in aluminium utensil because aluminium is a metal and lemon contains acid. The acid reacts with metal to give hydrogen and salt. This salt is toxic in nature which will spoil the food and makes it unfit to use
Citric acid + Aluminium \(\rightarrow \) Aluminium salt + Hydrogen \(\uparrow \)
(From lemon)                      (Toxic)