Water
The Universal Solvent
Water is commonly known as the universal solvent because of its ability to dissolve many substances. This is due to water's molecular structure.
A water molecule consists of one oxygen atoms and two hydrogen atoms. The side of the oxygen atom is slightly negatively-charged and the side with the hydrogen atoms is positive. These tiny "magnets" make water polar. Because of its polarity, many water molecules "stick" to each other through hydrogen-bonding, making water cohesive. Water's polar nature allows it to dissolve a variety of substances, earning it the name "the universal solvent".
Three Phases of Water
Water is one of the only compounds that commonly exists in all three phases on Earth: solid, liquid, and gas. Solid water is also known as ice.
Water becomes solid at 32 degrees Celsius. Unlike most other compounds, ice is less dense than water due to hydrogen bonding pushing molecules apart when cooled. This is the reason why icebergs float on water.
Ice melts and becomes liquid water at 32 degrees Celsius. Liquid water has many properties, including high surface tension and its ability to hold heat for a long time (high heat capacity).
Liquid water boils and becomes a gas, or water vapor, at 100 degrees Celsius. Water vapor can be condensed and reused as liquid water. Similarly, water that evaporates in nature forms clouds and condenses into rain.
Weathering
Water, usually in the form of rain, has shaped our environment through physical and chemical weathering of rocks and soil by carrying minerals and nutrients.
Physical Weathering
Physical weathering occurs when water does not change the mineral composition of the substance being weathered. This occurs when water seeps into cracks and fissures of rocks. As temperature lowers enough for the water to freeze, the ice will expand and gradually break apart the rock. This eventually produces small particles and sand.
Chemical Weathering
Chemical weathering occurs when water (from rain) contains dissolved gases and chemicals that gradually wear away the mineral composition of rocks, causing deterioration of the rock. Chemical weathering can be natural or caused by pollution.
Storing Thermal Energy
Water is capable of storing large amounts of heat, or thermal energy (high heat capacity). This means that large bodies of water can absorb and release heat without much change in temperature. For example, oceans absorb heat slowly in the summer and release heat slowly in the winter. The ability of large bodies of water to retain heat causes more stable, moderate climate in areas close to oceans and seas.
Industries and Health
Agriculture
Water plays a very important role in agriculture and farming. Crops rely on irrigation systems to transport water across fields. These crops are then harvested regularly and sold in the market to consumers like us.
Power
Water is important to power systems and industries as it is used in power plants. Hydroelectric power plants provide water to wind turbines through kinetic energy. The pooled water is turned into steam to generate electricity by spinning the turbine.
Health
Advances in water treatment and construction of sanitary sewers have positively impacted health of citizens globally. Centuries ago, people dumped waste and sewage into bodies of water, contaminating open water sources and facilitating the spread of disease. Since then, health officials have tried to establish safe and environment-friendly ways to dispose waste and treat water to prevent contamination and provide healthy drinking water.
Conservation
While water seems plentiful, it is important to conserve water so we can have the resources in the future to further improve the agriculture and power systems and human health. Only 2.5% of the Earth's water is fresh, a fraction of that is accessible. Every living being needs water to survive, and it is our responsibility to conserve water resources.
