Water and Solutions
Water is vital to all forms of life. The human body is made up of nearly 70 percent water. Almost two-thirds of the molecules in your body are water molecules. Not only are the body's cells filled with water but water is the medium in which most cellular events take place. Nutrients are moved in and out of cells by water. Water plays a life-sustaining role in the life of the body as well as in plant life. Without water life does not exist.
There are many properties of water that make it an important substance for life. For example, water stores heat efficiently because it heats more slowly and retains heat longer than many other substances. Heat is released through water evaporation. The human body cools itself down by sweating as the heat is released through the sweat. This allows the human body, and many organisms, to maintain a regulated internal temperature while the external temperature changes drastically.
Not only does water store heat, but it bonds to itself and other substances. The hydrogen bonds between water molecules cause the cohesion of liquid water. Cohesion is an attraction of substances of the same kind. When water and other liquids form drops, it is because of cohesion. Just like people hold hands to join together, molecules at the surface of water are linked together by hydrogen bonds. This attraction of water molecules causes a condition known as surface tension. Surface tension prevents the surface of water from breaking.
Just as cohesion is the attraction of substances of the same kind, adhesion is the attraction of substances of different kinds. Because of adhesion, water molecules are powered through a process called capillary action. This action allows water to move upward through the stem of a plant. As the water is attracted to the inside of a plant stem, the stem sucks the water up more strongly than gravity can pull it down, thus bringing life to the plant.
Not only does water store heat and bond itself to various substances, but water also dissolves other substances as well. For example, if salt is added to water the salt is dissolved leaving a saltwater solution. A solution is a mixture in which one or more substances are evenly distributed in another substance. There are many important substances in bodies that must be dissolved in order to be transported throughout the body. For example, sugar is vital to the human body. If it were not dissolved, it could not be carried throughout the body to other cells. Water dissolves the sugar.
The polarity of water enables many substances to dissolve in water. Polarity is when the ionic compounds are dissolved in water and the ions are then surrounded by polar water molecules. Ions are attracted to the ends of the water molecules with the opposite charge and become distributed resulting in a solution of an even mixture.
On the other hand, nonpolar molecules do not dissolve well in water. When a nonpolar substance like oil is placed in the water, the water molecules are more attracted to themselves and not to that of the nonpolar molecules. That is why the separation of water and oil takes place. As the polar molecules of water attract to each other, it forces the nonpolar molecules together causing a clear separation. This inability for nonpolar molecules to dissolve in water is important to organisms and life itself.
Because of the many properties at work, water remains a life-sustaining agent by which not only humans remain alive, but all life forms as well.
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