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

Acids are chemical compounds with a sour taste and appear in common items like curd, lemon, and vinegar, carrying lactic, citric, and acetic acid respectively. Bases, in contrast, are identified by their bitter taste and soapy feel. This comparison underscores the everyday presence and contrasting sensory characteristics of these compounds.

Acid and base properties are detected using specific indicators that change colors when interacting with chemicals found in everyday products like detergents, toothpaste, and hair dyes. Litmus paper demonstrates this property vividly, turning red in acids and blue in bases. Synthetic indicators such as methyl orange and phenolphthalein offer further precision by changing from red to yellow in bases or remaining clear in acids and turning pink in bases, respectively. Experimental tests with known acids (HCl, H2SO4, HNO3, CH3COOH) and bases (sodium hydroxide, calcium hydroxide, potassium hydroxide, magnesium hydroxide, ammonium hydroxide) consistently reveal these expected color transitions.

Chopped onions are used to create an olfactory indicator by absorbing their acidic vapors onto a cloth stored overnight. When treated with dilute HCl, the cloth retains its familiar onion scent, while application of sodium hydroxide neutralizes the acidity and eliminates the aroma. This experiment demonstrates how subtle sensory changes, such as smell, can effectively reveal the occurrence of acid-base neutralization reactions.

Acids reacting with metals, as seen with zinc in dilute sulfuric acid, produce a corresponding salt and hydrogen gas. When a base like concentrated sodium hydroxide is used with zinc under heat, a distinct salt and hydrogen gas form, although this behavior is not universal among all metals. Metal carbonates engage with acids to yield salt, water, and carbon dioxide, the latter confirmed by its transformation of calcium hydroxide into calcium carbonate. Metal hydrogen carbonates follow a similar pathway with acids, resulting in the creation of salt, water, and carbon dioxide.

A neutralization reaction is showcased by mixing dilute sodium hydroxide with phenolphthalein, which produces a pink hue due to its basic nature. Introducing hydrochloric acid shifts the balance to an acidic state, causing the pink color to disappear. Adding more sodium hydroxide restores the pink hue, demonstrating that acids diminish basic properties and bases reduce acidic characteristics. This experiment encapsulates the dynamic reversibility of acid-base neutralization reactions.

Metal oxides react with acids to produce a salt and water. In an experiment, copper oxide mixed with dilute hydrochloric acid transforms into copper chloride and water, as stirring gradually shifts the solution’s color to bluish green. The reaction illustrates the inherent chemical behavior where metal oxides consistently yield salt and water when combined with acids.

A non-metal oxide reacting with a base yields a salt and water. Calcium hydroxide, a base, when combined with carbon dioxide, produces a white precipitate of calcium carbonate. This reaction exemplifies how neutralization transforms a base into a salt through the interaction with a non-metal oxide.

Acids and bases generate ions in water, which enables them to conduct electricity. A demonstrated circuit with electrodes and a bulb revealed that dilute HCl and sodium hydroxide allow current flow, unlike non-ionizing solutions such as glucose or alcohol. In water, HCl dissociates into hydronium and chloride ions, while sodium hydroxide forms sodium and hydroxide ions. This clearly shows that ion production is the key factor behind the electrical conductivity observed in acids and bases.

Mixing an acid or base with water decreases the concentration of ions per unit volume, a process known as dilution. This reaction is highly exothermic, releasing substantial heat when the substances are combined. To prevent hazardous splashing, acid must be added slowly to water with constant stirring, rather than adding water to acid.

The pH scale, ranging from 0 to 14, classifies substances as acidic, neutral, or basic, with values below 7 indicating acidity and above 7 indicating basicity. Strong acids near 0 and strong bases near 14 exhibit reactive properties that can cause burns through local heating effects. Natural systems depend on a balanced pH, as acid rain can disrupt aquatic habitats and soil pH impacts plant growth. Human health relies on regulated acid levels for efficient digestion and dental safety, while various organisms use acids for defense countered by bases to neutralize their harmful effects.

Salts display varied pH levels determined by the strength of their acid and base components. Salts resulting from a strong acid and a strong base exhibit a neutral pH of 7. In contrast, salts formed from a strong acid and a weak base are acidic with pH values below 7. The nature of salts, whether neutral, acidic, or basic, directly reflects the characteristics of their combining elements.

Sodium chloride, widely recognized as common salt, is fundamentally basic because it originates from a weak acid and a strong base, yielding a pH above 7. Its everyday presence goes beyond culinary use, serving as a key raw material in chemical conversions. The salt is vital in the production of caustic soda, baking soda, washing soda, and bleaching agents, illustrating its versatile applications. This multifaceted role connects daily life with essential industrial processes.

Electrolysis of salt water, known as the Chlor Alkali process, produces sodium hydroxide, chlorine gas, and hydrogen gas. Chlorine gas is employed in water treatment, swimming pool maintenance, PVC production, disinfectant formulation, and manufacturing of chlorofluorocarbons and pesticides. Hydrogen gas finds use as a fuel and in the production of margarine and fertilizers, while sodium hydroxide serves in metal processing.

Common salt is transformed into baking soda by treating it with water, carbon dioxide, and ammonia, producing ammonium chloride alongside the sodium hydrogen carbonate. Its unique chemistry makes it integral to manufacturing soaps, detergents, paper, and artificial fibers. Additionally, baking soda serves multiple roles in cooking—as an antacid, an ingredient in fire extinguishers, and a leavening agent that releases carbon dioxide to create a spongy, fluffy texture.

Washing soda is produced by recrystallizing sodium carbonate, with baking soda and A2CO3 added to create a product that gives food a spongy and floppy texture. The process converts raw sodium carbonate into a compound with multiple applications. It plays a key role in manufacturing glass, soap, and paper. Additionally, it is essential in producing borax and serves as a cleaning agent for permanent removal.

Bleaching powder is produced by treating calcium hydroxide with chlorine gas generated during the Chlor Alkali process, resulting in a strong oxidizing compound. It is used to whiten cloth, paper, jute, and linen fibers during their manufacture. Its oxidizing properties are exploited in industries while its disinfectant qualities help maintain hygiene in public spaces such as near toilets and garbage bins.

Gypsum heated at 373 kelvins loses its water molecules to form calcium sulphate hemihydrate, widely known as plaster of Paris. Its name derives from the 18th century when Paris became a hub for extensive gypsum mining and large-scale production of the plaster. The material's versatility is evident in its medical use for supporting broken bones and in its role in crafting models and toys.