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25.9 x 38.6 cm ⏐ 10.2 x 15.2 in (300dpi)
CHARLES D. WINTERS / SCIENCE PHOTO LIBRARY CHARLES D. WINTERS / SCIENCE PHOTO LIBRARY
Potassium reacting with water. Water being dripped from the tip of a burette (at top centre) into a dish containing potassium metal. Potassium (chemical symbol K) is a silver-white, alkali metal. It reacts violently and exothermically (generating heat) with water (chemical symbol H2O), yielding potassium hydroxide (KOH) and hydrogen gas (H2). The generated heat causes the hydrogen to ignite in air, burning with a violet flame due to the presence of vaporised potassium. The chemical equation for this reaction is: 2K + 2H2O ----> 2KOH + H2 Potassium metal is usually stored under kerosene because it oxidises when exposed to air.
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