Properties of water equal to that of the hydrogen ion (), which gives a pH of 7 at 25 °C. Action of water on rock over long periods of time typically leads to weathering and water erosion, physical processes that convert solid rocks and minerals into soil and sediment, but under some conditions chemical reactions with water occur as well, resulting in metasomatism or mineral hydration, a type of chemical alteration of a rock which produces clay minerals. It also occurs when Portland cement hardens. Water ice can form clathrate compounds, known as clathrate hydrates, with a variety of small molecules that can
Water-reactive substances liberate toxic gas when in contact with water are recognised for their hazardous nature in the 'Approved Supply List,' or the list of substances covered by the international legislation on major hazards many of which are commonly used in manufacturing processeses. The alkali metals (Li, Na, K, Rb, Cs, and Fr) are the most reactive metals in the periodic table - they all react vigorously or even explosively with cold water, resulting in the displacement of hydrogen. The Group 1 metal (M) is oxidised to its metal ions, and water is reduced to hydrogen gas (H) and hydroxide ion (OH),