ACIDS, BASES AND SALTS in 1 Shot FULL CHAPTER IN ANIMATION ||| NCERT SCIENCE Class 10th Chapter 2

Acids are sour chemical compounds, present in items like curd, lemon, and vinegar. Bases are bitter and soapy, found in detergents, toothpaste, and hair dyes. The presence of acids and bases can be tested using indicators. Litmus, a natural indicator from lichens, turns blue litmus to red in acid and red litmus to blue in base. Other natural indicators include red cabbage, turmeric, and hibiscus. Synthetic indicators like methyl orange and phenolphthalein also change color in the presence of acids and bases.

Olfactory indicators, such as onion, vanilla essence, and clove oil, change their smell in acidic or basic solutions. For example, onion's smell is retained in acid but disappears in a base. Acids react with metals to produce salt and hydrogen gas (e.g., zinc with sulfuric acid forming zinc sulfate). Bases react with some metals to form salt and hydrogen gas as well (e.g., zinc with sodium hydroxide forming sodium zincate).

Metal carbonates and metal hydrogen carbonates react with acids to produce salt, water, and carbon dioxide. An example is sodium carbonate or sodium hydrogen carbonate reacting with HCl. The CO2 gas can be identified by passing it through calcium hydroxide solution, which forms a white precipitate. Neutralization reactions occur when acids and bases react to form salt and water, where the acidic and basic natures cancel each other out.

Metal oxides react with acids to form salt and water, as seen when copper oxide reacts with HCl to form copper chloride. Non-metallic oxides react with bases to produce salt and water; for instance, calcium hydroxide treated with carbon dioxide forms calcium carbonate.

Both acids and bases conduct electricity when dissolved in water because they produce positive (cations) and negative (anions) ions. Dilution, the process of mixing acids or bases with water, decreases the concentration of ions and is a highly exothermic reaction. Acids should always be added to water slowly to prevent splashing and burns. The pH scale (0-14) measures the strength of acids and bases: below 7 is acidic, above 7 is basic, and 7 is neutral. Strong acids are closer to 0, strong bases closer to 14.

pH is crucial for aquatic life, plant growth (farmers test soil pH), and human health. The stomach's hydrochloric acid aids digestion, and excess acid (acidity) is treated with bases (antacids). Tooth decay occurs when mouth pH drops below 5.5 due to acid produced by bacteria. Living things use acids and bases for defense, like bee stings (acidic, treated with baking soda) and nettle stings (acidic, treated with a dock plant).

Salts can be neutral (strong acid + strong base, pH 7), acidic (strong acid + weak base, pH < 7), or basic (weak acid + strong base, pH > 7). Sodium chloride, or common salt, is a key ingredient in making several useful chemicals. The Chlor-Alkali process involves passing electricity through an aqueous solution of sodium chloride to produce sodium hydroxide, chlorine gas, and hydrogen gas.

Chlorine gas is used for water treatment, PVC, disinfectants, and pesticides. Hydrogen gas is used as fuel, in margarine, and fertilizers. Sodium hydroxide is used in degreasing metals, soaps, detergents, paper, and artificial fibers. Baking soda (sodium hydrogen carbonate) is manufactured by treating common salt with water, carbon dioxide, and ammonia. It's used in cooking (making food spongy and fluffy by releasing CO2), as an antacid, and in fire extinguishers.

Washing soda (sodium carbonate) is obtained by recrystallization of sodium carbonate and used in glass, soap, paper industries, manufacturing borax, as a cleaning agent, and for removing water hardness. Bleaching powder (calcium oxychloride) is prepared by treating calcium hydroxide with chlorine gas. It's used for whitening cloth and paper, as an oxidizing agent, and for disinfecting. Plaster of Paris (calcium sulfate hemihydrate) is made by heating gypsum, widely used in medicine for setting broken bones and in making toys and models.