The second chapter in Science textbook is 'Acids, Bases and Salts'.
Indicators
Indicators are substances which indicate the acidic or basic nature of the solution by the colour change.
Types of Indicators
Natural indicators
Indicators obtained from natural sources are called Natural Indicators.
Litmus, turmeric, red cabbage, China rose, etc., are some common natural indicators used widely to show the acidic or basic character of substances.
Olfactory indicators
Substances which change their smell when mixed with acid or base are known as Olfactory Indicators. For example; Onion, vanilla etc.Synthetic indicators
Indicators that are synthesized in the laboratory are known as Synthetic Indicators. For example; Phenolphthalein, methyl orange, etc.
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Acids
Acids are sour in taste, turn blue litmus red, and dissolve in water to release H+ ions.
Example: Sulphuric acid (H2SO4), Acetic Acid (CH3COOH), Nitric Acid (HNO3) etc.
Acids are classified into two categories - Natural acids and Mineral acids.
Properties of Acids
- Acids have a sour taste.
- Turns blue litmus red.
- Acid solution conducts electricity.
- Release H+ ions in aqueous solution.
Bases
Bases are bitter in taste, have soapy touch, turn red litmus blue and give hydroxide ions (OH–) in aqueous solution.
Examples: Sodium hydroxide (caustic soda) – NaOH
Calcium hydroxide – Ca(OH)2
Potassium hydroxide (caustic potash) – (KOH)
Bases are classified into two categories - Water soluble and Water insoluble.
Salts
Salts are the ionic compounds which are produced after the neutralization reaction between acid and base.
Salts are electrically neutral.
Characteristics of Salt
- Most of the salts are crystalline soild.
- Salts may be transparent or opaque.
- Most of the salts are soluble in water.
- Solution of the salts conducts electricity in their molten state also.
- The salt may be salty, sour, sweet, bitter and umami (savoury).
- Neutral salts are odourless.
- Salts can be colourless or coloured.
The topics discussed in this chapter are as follows:
- Ionisable and non-ionisable compounds
- Arrhenius theory of acids and bases
- Bronsted Lowry theory
- Dilution
- Universal indicator
- Importance of pH in everyday life
- Manufacture of Acids and Bases
Students can view and download the chapter from the link given below.
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NCERT Solutions for Chapter 2: Acids, Bases and Salts
Also Check
Chapter 1: Chemical Reactions and Equations
Chapter 3: Metals and Non-Metals
Chapter 4: Carbon and its compounds
Chapter 5: Periodic Classification of Elements
Chapter 6: Life Processes
Chapter 7: Control and Coordination
Chapter 8: How do organisms reproduce?
Chapter 9: Heredity and Evolution
Chapter 10: Light - Reflection and Refraction
Chapter 11: The Human Eye and the Colourful World
Chapter 12: Electricity
Chapter 13: Magnetic Effects of Electric Current
Chapter 14: Sources of Energy
Chapter 15: Our Environment
Chapter 16: Sustainable Management of Natural Resources
Check out Frequently Asked Questions (FAQs) for Chapter 2: Acids, Bases and Salts
Which acid is present in sour milk or curd?
Lactic acid
What are the pH values of distilled water and common salt solution?
Both are neutral and have pH close to 7.
Which bases are called alkalies? Give an example of an alkali.
Soluble bases are called alkalies. For example, sodium hydroxide (NaOH).
Name the chemical substance present in thick white and yellowish clouds present in the atmosphere of Venus.
Sulphuric acid
Name the hardest substance in the body.
Tooth enamel (Calcium phosphate)
