Acids are those chemical substances that gives hydrogen ions when dissolved in water.

For example: HCl -----> H⁺ + Cl^-
H2SO4 -----> 2H⁺ + SO4^--

Acids which undergo almost complete dissociation in aqueous solution and produce high concentration of hydrogen ions is called strong acids.
For eg.Hcl, H₂SO₄.

Acids that undergo partial dissociation in aqueous solution and produce less concentration of hydrogen ions is called weak acids.
For eg.Carbonic acid(H₂CO₃), Formic acid(HCOOH)

Acids which are obtained from living organisms and have hydrocarbons are called organic acids.
For eg.Acetic acid(CH₃COOH), Formic acid(HCOOH)

Acids which are obtained from minerals and do not have hydrocarbons are called inorganic acids.
For eg. Hydrochloric acid(Hcl), Sulphuric acid(H₂SO₄)

Two properties of acids are listed below:
i. It taste sour.
ii. It is corrosive in nature.
iii. It changes blue litmus paper to red and methyl orange to red.

Any two chemical properties of acids with balanced chemical eqn. are:
i. It reacts with base to produce salt and water.
Hcl + NaOH -------->Nacl + H₂O
ii. It dissolve in water and give hydrogen ions.
Hcl --------->H⁺ + cl^-

Any three uses of acids are listed below:
i. It is used in industries and laboratories.
ii. It is used to kill germs.
iii. It is used in baking powder.

We bring acids in domestic use by following way:
i. It is used for preserving and flavoring foods.
ii. It is used for washing eyes and wounds.
iii. It is used in soft drink and soda water.
iv. It is used to make pickle.
v. It is used in medicine as the source of vitamin C.

Metallic oxides or hydroxides are called base. In broader sense, base are oxide of metals or hydrogen that are basic in nature.
For eg. PbO, CuO, etc.

The base that dissolve in water and produce hydroxyl (Oh^-) ions are called alkalis.
For example: NaOH, KOH, etc.

The uses of common salts are:
i. It is used in our food as preservative.
ii. It is used to reduce the hardness of water.
iii. It is used for plastering the fractured bones.
iv. It is used in chemical fertilizer.
v. It is used in dry cell as electrolyte.
vi. It is used to make white pigments of eyes.

We know, acids are acidic in nature but base are basic in nature. Acids contains hydrogen ions (H⁺) which stimulate the taste buds that detect sour taste. Bases contain (OH^-)ions which stimulate the taste buds that detects bitter taste. Therefore, acids are sour in taste but bases are bitter.

Any two physical properties of alkalis are:
i. They are soapy in touch and bitter in taste.
ii. Strong base or alkalis burn our skin.

Any two chemical properties of base wit chemical rxⁿ are:
i. Alkalis react with acid to form salt and water.
NaOH + Hcl --------> Nacl + H₂O
ii. Alkalis librate ammonia from ammonium salts.
NaOH + NH₄Cl ----------> Nacl + H₂O + NH₃

The process of mixing base and acids together to lose their properties and neutralize the substance is meant by neutralization reaction.
Example: Hcl + NaOH ---------> Nacl + H₂O

The major uses of base are:
i. It is used to make soap, detergent, etc.
ii. It is used to make bleaching powder.
iii. It is used to remove grease and stain from clothes.
iv. It is used for softening hard water.
v. It is used for purification of sugar and production of cements.

Salt is a chemical substance which is formed by partial or complete replacement of hydrogen ions of and acid by a metal or ammonium radical.
i. By direct combination of metal and non-metals.
ii. By the reaction of metals with acids.

Any three properties of salts are:
i. Salt are water soluble and insoluble both.
ii. Salts are amorphous and crystalline both.
iii. Salt are electrovalent compounds.

Bases are those substances which may or mayn't dissolve in water but alkalis are the bases which are dissolved in water. Insoluble bases are not alkalis. Therefore we can say that, all alkalis are bases but all bases are not alkalis.

We know, sodium hydroxide is an alkali which produces high concentration of hydroxyl ions in a solution but ammonium hydroxide produces low concentration. So, sodium hydroxide is a stronger and ammonium hydroxide is a weak base.

i. Hcl + KoH ----------> H₂O + Kcl
ii. 2KoH + H₂SO₄ -----------> K₂SO₄ + 2H₂O
iii. CuO + H₂SO₄ ----------> CuSO₄ + H₂O
iv. 2NaOH + H₂SO₄ ---------> Na₂SO₄ + 2H₂O
v. H₂SO₄ + Cu(OH)₂ ---------> CuSO₄ + 2H₂O

i. Boric acid: Washing eyes and wounds.
ii. Nitric acid: Making explosives, plastics and dyes.
iii. Tartaric acid: Used in baking powder.
iv. Sodium hydroxide: Making soap, detergents, paper, etc.
v. Calcium oxide: Softening hardwater, purifying sugar, etc.
vi. Calcium sulphate: plastering fractured bones.
vii. Aluminium chloride: Used in dry cell as an electrolyte.
viii. Zinc sulphate: Making pigment in eyes.

Any three applications of neutralization reactions are:
i. Farmers use lime to neutralize the acidity of soil.
ii. We can neutralize formic acid by using soap.
iii. Acetic acid is used to neutralize the acid injected by the bumble bee in our skin.

Hcl is kept in plastic or glass bottles because these are more durable against the chemical attack of this harsh acid than others.

We know that alkalis are water soluble but bases are metallic oxides and hydroxide which may or may not be soluble in water( such as NaOH, KOH, Mg(OH) etc...) and they are alkalis where as other most of the bases are insoluble in water( such as HgO, CuO, etc...) which are only bases but not alkalis. Hence, all alkalis are bases but all bases are not alkalis.

Acetic acid has a very low concentration of hydrogen ions ( H⁺) in its aqueous solution. So, acetic acid is called weak acid.

Sodium chloride stimulates the taste buds of our tongue that detects the salty taste. So, sodium chloride is salty

Ammonium hydroxide or solution of ammonia (NH₄OH) is weak alkali because it produce the low concentration of hydroxyl ions in the aqueous solution( which dissolved in water) .