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 crisis in the Democratic Republic of the Congo DRC, the actual number of people without water access is increasing at a significantly higher rate in urban areas because of faster population growth. The average annual growth rate of the urban population over the time period from 2010 to 2015 was estimated at 4 percent, compared to a population growth rate of 1.9 percent in rural areas. The population living in urban areas is estimated at 42 percent. The rapid population growth in urban areas is associated with the expansion of the urban sprawl and poses major difficulties in establishing adequate water infrastructure. Many peri-urban watersheds are being impacted