Water

Looking at water, you might think that it's the most simple thing around. Pure water is colorless, odorless, and tasteless. But it's not at all simple and plain and it is vital for all life on Earth. Where there is water there is life, and where water is scarce, life has to struggle. So, two most important questions we need to ask are: what is it about water that makes it so important to us? What are the physical and chemical properties of water that make it so unique and necessary? When you look at a glass of water, taste and smell it, it does look rather boring. Pure water is virtually colorless and has no taste or smell. But the hidden qualities of water make it a most interesting subject for living things. What’s unique about water is that it is the only natural substance that is found in all three states - liquid, solid (ice), and gas (steam). Water also has a very high surface tension. In other words, water is sticky and elastic, and tends to clump together in drops rather than spread out in a thin film. As we all know, water tends to stick together, as in a drop, and it sticks to glass, cloth, organic tissues, and soil. If you dip a paper towel into a glass of water and the water will "climb" onto the paper towel. In fact, it will keep going up the towel until the pull of gravity is too much for it to overcome. When u spill a glass of water on the table and rush to get a paper towel, first u must thank surface tension, which keeps the liquid in a nice puddle on the table, instead of a thin film of sugar that spreads out onto the floor.

The unique qualities and properties of water are what make it so important and basic to life. Water is of major importance to all living things; in some organisms, up to 90 percent of their body weight comes from water. Up to 60 percent of the human body is water, the brain is composed of 70 percent water, and the lungs are nearly 90 percent water. Each day humans must replace 2.4 liters of water, some through drinking and the rest taken by the body from the foods eaten. Also our everyday life would be impossible without water. All the things you do at home: drinking, preparing food, bathing, washing clothes and dishes, brushing your teeth, watering the yard and garden, and even washing the dog are only possible thanks to it. So, looking at this glass of water, we look in fact at pure life. There just wouldn't be any you or me, without the existence of this incredible liquid.

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