Chapter 5 - Acids, Bases and Salts Notes
1. The substances that tastes sour are called acid. Example: Curd, Lemon juice, Vinegar etc.
2. Substance which is bitter in taste are called base. Example: calcium hydroxide, ammonium hydroxide, magnesium oxide etc.
3. The substances which are used to test the acidic or basic nature are known as indicators.
4. Some naturally occurring indicators such as turmeric, litmus, China rose petals (Gudhal), etc.
5. The most commonly used natural indicator is litmus which is extracted from lichens.
6. It has a mauve (purple) colour in distilled water. It turns red when added to an acidic solution and blue when added to a basic solution.
7. Turmeric is natural indicator which turns from yellow to red in alkaline (basic) solution.
8. China rose petal solution turns dark pink in acidic solution and green in basic solution. It is also a natural indicator.
9. There are also some substances which are neither basic nor acidic. The solutions (substances) which do not change the colour of either red or blue litmus are called neutral substances or solutions. Example: distilled water, common salt solution, sugar solution, etc.
10. The reaction between an acid and base is known as neutralisation. Salt and water are produced in this process with the evolution of heat.
Acid + Base ➝ Salt + Water (Heat is evolved)
The following reaction shows neutralization:
11. In neutralisation reaction salt is formed which may be acidic, basic or neutral in nature.
12. Neutralisation reaction is helpful in everyday life. It is used in case of indigestion, ant bite, soil treatment, etc.
13.
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