Phenolphthalein is colorless in acidic and neutral solutions, turning pink/magenta in basic solutions with pH > about 8.2-10. It is commonly used in acid-base titrations. Methyl orange is red in acidic and yellow in basic. Litmus is purple in neutral, red in acid, blue in base. Natural indicators like turmeric, beetroot also show color changes.
Explanation:
Potassium (K) is an alkali metal placed at the very top of the reactivity series. It reacts violently with water and air, requiring storage in kerosene. Gold, silver, and copper are noble or less reactive metals placed at the bottom of the series, often found in the free state.
Explanation:
Bakelite is a thermosetting phenol-formaldehyde resin with excellent heat resistance and electrical insulation properties, making it suitable for switches, handles, and electrical fittings. Polythene and PVC are thermoplastics that soften on heating. Polystyrene is brittle and not highly heat resistant. Thermosets do not melt upon reheating.
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