CBSE Class 10 Science Chapter 2 Revision Notes

Chapter 2: Acids, Bases and Salts Revision Notes

Classification of Matter

on the basis of

a) Composition– elements, compounds, and mixes

b) State of matter- Solids, liquids and gases

c) soluble matter – suspensions, colloids, and solutions

  • Homogeneous and heterogeneous mixes are two types of mixtures.
  • Covalent and ionic compounds are two different types of chemicals.

What Is the Difference Between an Acid and a Base?

Physical examination

There are two physical tests that may be used to determine if an acid or a base is present.

a. Taste

  • An acid has a sour flavour, whereas a base has a bitter flavour.
  • Because an acid or a base might be polluted or caustic, this way of tasting is not recommended.

b. Effect on Indicators by acids and bases

  • When a chemical substance comes into touch with an acid or a base, it changes its physical qualities, most commonly colour or scent.

The following are some regularly used indicators and the many colours they display:

a) Litmus paper

  • Purple in a neutral solution
  • In an acidic solution, the colour is red.
  • Blue is the most basic answer.
  • Litmus is also available as paper strips in two colours: red and blue litmus.
  • A damp blue litmus paper turns red when exposed to an acid.
  • A base changes the colour of wet red litmus paper to blue.

b) Methyl orange

  • Orange in a neutral solution
  • In an acidic solution, the colour is red.
  • Yellow in basic solution

d) Phenolphthalein

  • In a colourless neutral solution
  • In an acidic solution, the substance stays colourless.
  • Pink is the most basic answer.


  • Water contains acids and bases.
  • Acids and bases breakdown into their respective ions when introduced to water and aid in the conductivity of electricity.

What is the distinction between a base and an alkali?

  • Acids react with bases to neutralise them.
  • Metal oxides, metal hydroxides, metal carbonates, and metal bicarbonates make up these compounds.
  • The majority of them are water insoluble.
  • An alkali is a base in aqueous solution (mainly metallic hydroxides).
  • It dissolves in water and then dissociates to produce the OH ion.
  • All bases are alkalis, but not all alkalis are bases.

Hydronium ion

  • A coordinate covalent bond is created when a hydrogen ion receives a lone pair of electrons from the oxygen atom of a water molecule.


  • Dilution is the process of decreasing a solution’s concentration by adding more solvent (typically water).
  • It’s a really exothermic reaction.
  • Acid must be put to water, not the other way around, to dilute it.


  • When all molecules of an acid or a base disintegrate entirely in water to produce their corresponding ions, H+(aq) for acid and OH(aq) for base).

Weak acid or base: When just a few molecules of an acid or base dissociate in water to produce their corresponding ions, H+(aq) for acid and OH(aq) for base.

Universal Indicator

  • The pH range of a universal indicator is 0 to 14, and it represents the acidity or alkalinity of a solution.
  • The pH of a neutral solution is 7.


  • The pH scale spans from 0 to 14, with 0 being the most acidic and 14 being the most alkaline.
  • If the acidic solution has a pH of 7, it is said to be acidic.
  • If the pH is more than 7, use a basic solution.

Importance of pH in everyday life

1. Plant and animal pH sensitivity

  • pH affects both plants and animals. At a given pH value, vital life activities such as food digestion, enzyme functioning, and hormone production take place.

2. A soil’s pH

  • The pH of a soil that is ideal for plant or agricultural growth is 6.5 to 7.0.

3. The digestive system’s pH

  • In human stomach, digestion takes place at a precise pH range of 1.5 to 4.
  • HCl in our stomach influences the pH of enzyme interactions as food is being digested.

4. The role of pH in tooth decay

  • When the teeth are exposed to an acidic environment with a pH of 5.5 or lower, tooth decay occurs.

5. The pH of animal and plant self-defense

  • Animals and plants employ acidic compounds as a self-defense strategy.
  • For self-defense, bees and plants like nettle emit a very acidic chemical. These acidic chemicals released have a specified pH.


  • A salt is a compound made up of an acid’s anion and a base’s cation.
  • KCl, NaNO3, CaSO4, and other salts are examples.
  • The neutralisation reaction of an acid and a base is commonly used to make salts.

formation of saltSource:

Common salt

  • Because it is used in cooking all around the world, sodium chloride (NaCl) is known as common salt.

Family of Salt

  • Salts with the same cation or anion are classified as belonging to the same family. NaCl, KCl, and LiCl, for example.

The salts’ pH

  • In nature, a salt comprising a strong acid and a strong base will be neutral. pH 7.0 (approx.).
  • In nature, a salt of a weak acid and a strong base will be basic. pH greater than 7.
  • Acidic in nature is a salt comprising a strong acid and a weak base. pH is less than 7.
  • A pH test is used to detect the pH of a salt of a weak acid and a weak base.

Bleaching powder

  • Bleaching powder produces chlorine when it comes into contact with water, which is responsible for the bleaching effect.

Baking soda

  • Sodium hydrogen carbonate is the chemical name for this substance.
  • NaHCO3 is the chemical formula.


  1. Textile manufacturing

  2. Paper manufacturing

  3. Antiseptic

Washing soda

  • Sodium hydrogen carbonate is the chemical name for this substance.
  • NaHCO3 is the chemical formula.

Preparation (the Solvay method) –

a. Limestone is heated in the following way: CaCO3 + CaO + CO2

b. CO2 is passed through a concentrated sodium chloride/ammonia solution:

NaHCO3(aq) + NH4Cl = NaCl(aq) + NH3(g) + CO2(g) + H2O(l) (aq)


In the glass, soap, and paper industries, for example.

  1. Water softening

  2. A housecleaner

Plaster of paris

  • Heating gypsum, CaSO4.2H2O (s) to 100°C (373K) yields CaSO4. 12 H2O and 3/2 H2O.
  • Plaster of Paris is made up of CaSO4 and 12 H2O.
  • CaSO4. 12 H2O denotes that two CaSO4 formula units share one water molecule.
  • Casts are used to help mend fractures.



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