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 management in the Metropolitan Region of São Paulo rivers, creeks and other tributaries is declining by the year given that only half of the dwellings have some sort of solid waste collection system and most of the solid waste collected continues to be disposed of in the reservoir as many poor households still have no formal wastewater collection and disposal at all. Water management in the Metropolitan Region of São Paulo Water management in the Metropolitan Region of São Paulo, Brazil faces several challenges, including pollution of drinking water reservoirs that are surrounded by slums, water scarcity leading to conflicts with the Campinas Metropolitan area to the north,