Water
Overview
Water, with the chemical formula H₂O, is a colorless, odorless, and tasteless liquid formed by covalent bonds between two hydrogen atoms and one oxygen atom. It covers approximately 71% of Earth's surface and constitutes the largest component of living organisms. Water serves as an essential resource for human society across all domains, including life support, climate regulation, industrial activities, and culture and religion.
Main Content
1. Physical and Chemical Properties
Water exhibits unique properties due to hydrogen bonding between molecules. Notably, its density reaches a maximum at 4°C, causing ice to float on water (solid density < liquid density), which allows aquatic ecosystems to survive in winter. Its specific heat capacity (4.186 J/g·K) is very high, buffering temperature changes, and its high latent heat of vaporization makes it effective as a coolant. Additionally, as a polar solvent, it readily dissolves ionic substances and polar molecules, earning it the nickname 'universal solvent.'
2. Global Cycle and Distribution
Water circulates through the hydrosphere (oceans, glaciers, groundwater, and atmospheric water vapor), transporting energy and matter. Approximately 97.5% of Earth's total water is saline (seawater), with only 2.5% being freshwater. Of this freshwater, about 68.7% is locked in glaciers and permanent snow, 30.1% is groundwater, and less than 0.3% exists in the form of rivers, lakes, and atmospheric water vapor. Thus, accessible freshwater is extremely limited.
3. Living Organisms and Water
All living organisms consist of 50–70% water by weight. Water plays key roles as a cellular solvent, a medium for metabolic reactions, a regulator of body temperature, and a transporter of nutrients and waste. In photosynthesis, water acts as an electron donor, and water is also produced during respiration. Water scarcity leads to severe consequences such as dehydration, impaired kidney function, and death.
4. Human Society and Water
- Drinking Water and Sanitation: According to the WHO, approximately 2 billion people worldwide lack access to safe drinking water, and waterborne diseases (cholera, typhoid fever, etc.) are among the leading causes of death.
- Agriculture: About 70% of global freshwater withdrawals are used for irrigation agriculture. Improving irrigation efficiency and water-saving technologies are crucial.
- Industry: Large amounts of water are required for power plant cooling, manufacturing processes, and semiconductor cleaning. Industrial wastewater treatment is a key challenge in preventing environmental pollution.
- Culture and Religion: Water is revered as a symbol of purification, rebirth, and life in many religions (Christian baptism, Hindu worship of the Ganges River, Islamic rituals).
5. Water Scarcity and Conflict
Climate change, population growth, and pollution are intensifying water scarcity worldwide. The United Nations projects that by 2025, two-thirds of the global population will experience water stress. Conflicts over transboundary water resources, such as the Nile, Tigris-Euphrates, and Indus rivers, are frequent. Water is regarded as a future 'strategic resource.'
Latest Trends
As of 2024–2025, key trends related to water include:
- Climate Change Impacts: Extreme droughts and floods are increasing simultaneously, making it urgent to strengthen the resilience of water management infrastructure. Record-breaking droughts occurred in parts of Europe and Asia in 2024.
- Desalination Technology Advances: The efficiency of reverse osmosis membrane technology has improved by over 15%, and desalination plants based on renewable energy (solar, wave power) have entered the commercialization stage. Large-scale investments continue in Middle Eastern countries such as Saudi Arabia and the UAE.
- Smart Water Management: IoT sensors, AI-based leak detection, and real-time water quality monitoring systems are being introduced into urban water supply systems, reducing water loss rates by 20–30% in many cases.
- Growing Awareness of Water Footprint: The concept of 'water footprint,' which considers the amount of water (virtual water) used in product production, is expanding among consumers and businesses, emphasizing sustainable consumption patterns.
- International Cooperation: Following the UN 2023 Water Conference, countries are updating their Integrated Water Resources Management (IWRM) plans in line with the 'Water Action Decade' goals, and a global water security assessment report is scheduled for release in 2025.
Related Topics
- [[Water resources]]
- [[Climate change]]
- [[Desalination]]
- [[Water pollution]]
- [[Origin of life]]
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