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 including Beni, Bunia, Lisala, Lubumbashi, Kisangani and Mbuji-Mayi. Water supply from deep-drilled wells is limited to a small percentage of the population. Most of the approximately 1,000 wells were constructed between the 1960s and 1990s and have yields between 15 and 80 m³/h. Hand and mechanical pump wells and dug wells account for around 10 percent of the drinking water supply. In 2015, there were still around 1 million people without access to "improved" water. In 2015, 76% of the population had access to an "improved" water source, 96% and 40% in urban and rural areas, respectively. Water withdrawals per