Class 10 Science – NCERT Chapter 2
Acids, Bases and Salts — Simplest Notes + Easy Examples
These notes cover the main NCERT concepts in easy language and are useful for quick revision and exam
preparation.
1. What are Acids and Bases?
Acid: A substance that generally gives H+ ions in water and has a sour nature. Examples: hydrochloric acid
(HCl), sulphuric acid (H SO ), lemon juice (citric acid).
2 4
Base: A substance that gives OH− ions in water or accepts H+. Many bases feel soapy. Examples: sodium
hydroxide (NaOH), calcium hydroxide [Ca(OH) ].
2
Remember: Never taste a laboratory chemical to identify it.
2. Indicators
Indicator In Acid In Base
Litmus Blue → Red Red → Blue
Phenolphthalein Colourless Pink
Methyl orange Red Yellow
Example: If blue litmus turns red, the solution is acidic.
3. Acids and Metals
Many acids react with metals to form a salt + hydrogen gas.
Example: Zn + 2HCl → ZnCl2 + H2↑
The bubbles are hydrogen gas. Hydrogen burns with a characteristic 'pop' sound.
4. Acids and Metal Carbonates / Hydrogencarbonates
Acid + metal carbonate → salt + water + carbon dioxide
Acid + metal hydrogencarbonate → salt + water + carbon dioxide
Example: NaHCO3 + HCl → NaCl + H2O + CO2↑
CO2 turns lime water milky. This is a common test for carbon dioxide.
5. Acids and Bases React: Neutralisation
When an acid reacts with a base, the products are usually salt + water. This is called neutralisation.
Example: HCl + NaOH → NaCl + H2O
Daily-life example: Antacids contain mild bases that neutralise excess acid in the stomach.
6. Reaction of Acids with Metal Oxides
Acid + metal oxide → salt + water
Example: CuO + 2HCl → CuCl2 + H2O
Copper(II) oxide is a basic metal oxide, so it reacts with acid.
Class 10 Science | Chapter 2: Acids, Bases and Salts | Page 1
Acids, Bases and Salts — Simplest Notes + Easy Examples
These notes cover the main NCERT concepts in easy language and are useful for quick revision and exam
preparation.
1. What are Acids and Bases?
Acid: A substance that generally gives H+ ions in water and has a sour nature. Examples: hydrochloric acid
(HCl), sulphuric acid (H SO ), lemon juice (citric acid).
2 4
Base: A substance that gives OH− ions in water or accepts H+. Many bases feel soapy. Examples: sodium
hydroxide (NaOH), calcium hydroxide [Ca(OH) ].
2
Remember: Never taste a laboratory chemical to identify it.
2. Indicators
Indicator In Acid In Base
Litmus Blue → Red Red → Blue
Phenolphthalein Colourless Pink
Methyl orange Red Yellow
Example: If blue litmus turns red, the solution is acidic.
3. Acids and Metals
Many acids react with metals to form a salt + hydrogen gas.
Example: Zn + 2HCl → ZnCl2 + H2↑
The bubbles are hydrogen gas. Hydrogen burns with a characteristic 'pop' sound.
4. Acids and Metal Carbonates / Hydrogencarbonates
Acid + metal carbonate → salt + water + carbon dioxide
Acid + metal hydrogencarbonate → salt + water + carbon dioxide
Example: NaHCO3 + HCl → NaCl + H2O + CO2↑
CO2 turns lime water milky. This is a common test for carbon dioxide.
5. Acids and Bases React: Neutralisation
When an acid reacts with a base, the products are usually salt + water. This is called neutralisation.
Example: HCl + NaOH → NaCl + H2O
Daily-life example: Antacids contain mild bases that neutralise excess acid in the stomach.
6. Reaction of Acids with Metal Oxides
Acid + metal oxide → salt + water
Example: CuO + 2HCl → CuCl2 + H2O
Copper(II) oxide is a basic metal oxide, so it reacts with acid.
Class 10 Science | Chapter 2: Acids, Bases and Salts | Page 1
