Water (H2O) is one of the most important compounds on Earth, covering many fundamental aspects of life. It exists on Earth in solid, liquid, and gaseous states simultaneously, making water an integral part of the environment and ecosystems. Water's uniqueness stems from the nature of its molecules and environmental conditions, allowing it to play important roles in different climates and geographies.
Water is the solvent of life and can dissolve many substances, so it is called "water of life".
Water is a polar molecule, and the angle between the oxygen atoms and hydrogen atoms in the molecule is 104.5 degrees. The polarity of water molecules enables them to form hydrogen bonds, which is the main reason water has relatively high melting and boiling points. Water has three distinct states under normal conditions: solid ice, liquid water, and gaseous water vapor. Such diversity makes water the most common natural substance on earth.
Water is the only substance that exists simultaneously as a solid, liquid, and gas under normal Earth conditions.
The water cycle is the continuous exchange process of water between the atmosphere, soil, water bodies and organisms, covering processes such as evaporation, condensation, precipitation and runoff. Both are part of the Earth's hydrological cycle, where water plays an increasingly important role in nature. The evaporated water molecules rise into the air and become a gas; when the water vapor cools, it falls as a liquid, like rain.
Why can water exist in these three states at the same time on earth? This is due to the environmental conditions of the Earth. Scientists point out that the atmospheric pressure and temperature on Earth are just close to the triple point of water, which means that under certain conditions, solid, liquid and gaseous water can exist at the same time. The property of this triple point is that water remains stable even in changing environments.
At the triple point of water, the solid, liquid and gaseous states of water can coexist, which is a unique aspect of water.
Water plays an important role in Earth's ecosystems, including supporting various life forms, ecological balance and climate regulation. Water's heat capacity properties allow it to regulate climate, storing and releasing heat, thereby influencing climate patterns around the world. The flow of water also promotes soil nutrient recycling and plant growth, continuously supplying water for daily life.
More than that, water use is critical in the global economy. About 70% of freshwater is used for agriculture, and fisheries have always been the main source of food in many places around the world, providing 6.5% of global protein. Water transport is also crucial in long-distance trade, with many goods being transported via oceans, rivers and lakes.
In the face of global warming and its impact on water resources, water management has become an important issue today. Understanding the properties of water and the impact of environmental changes is key to our future survival and development. How we can effectively utilize and protect our water resources in the future will also be a question we need to think deeply about.