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Water Properties Essential to Life

Bekah Link, Courtney Stringer, Jessica Watson, Ice Strickland, and Melissa Rogers

Water

The Universal Solvent

Water is essential to life because of four important properties: cohesion and adhesion, water's high specific heat, water's ability to expand when frozen, and its ability to dissolve a wide variety of substances.

Water Absorbs And Releases Heat

Water is often regarded as a universal solvent because of its ability to dissolve a wide variety of substances. The only exceptions to this rule is water's inability to dissolve substances that are non-polar (electrons are dispersed evenly throughout) and thus hydrophobic (repelled by water) in nature. Water has the ability to dissolve many substances because it can pull apart the bonds of other substances. For example, when water (H20) dissolves table salt (NaCl), hydrogen's attraction to chlorine and oxygen's attraction to sodium is stronger than the ionic bonds that hold together NaCl. These attractions occur because hydrogen is positive and chlorine is negative. Likewise, negatively charged sodium is attracted to positively charged oxygen.

Cohesion and Adhesion

Water has a very high specific heat, which means it can take in a lot of heat before changing temperature. When compared to rubbing alcohol, for example, water takes longer to heat up and to cool down because of its high specific heat. Rubbing alcohol has a low specific heat, therefore it can't absorb as much heat as water.

Why is this important to life?

One way cohesion and adhesion are important to life is capillary action. Capillary action is vital for plant life and is the result of adhesion and cohesion. The adhesion of water to vessels inside a plant allows water to travel throughout a plant. Cohesion holds the water together so all of the liquid is dragged upward into the plant against gravity.

Cohesion (the attraction of water molecules to other water molecules), adhesion (the attraction of water molecules to different molecules), surface tension, and capillary action play huge roles in life. Water molecules themselves are held together by hydrogen bonds, the weakest bonds. Negatively charged oxygen atoms are attracted to positively charged hydrogen atoms and bond with hydrogen bonds to form H2O. Cohesion is the attraction of these H2O molecules. Adhesion is the attraction of water molecules to different molecules.

Why is this important to life?

Density

Why is this important to life?

Surface Tension

Water's ability to absorb a lot of energy before changing temperature (specific heat) regulates an organism's body temperature. For example, humans can regulate a temperature of 98.6 degrees Fahrenheit while it's snowing outside. Likewise, when it's hot outside, our bodies release sweat to cool our bodies down. Because sweat is 99 percent water, sweat can absorb a lot of heat from our bodies and release it as it evaporates. The oceans also regulate the earth's atmosphere and keep the planet from heating up too much during the day by absorbing heat and cooling off too much at night by releasing heat. If water didn't absorb all of this heat, earth would turn into a huge desert; if water didn't release heat, earth would be a frozen planet. This is also why coastal areas are more temperate than non-coastal areas.

Water is one of the few substances on earth whose solid form floats on its liquid form, which in basic terms means, ice floats on water. Most liquids condense as temperature drops and stays condensed when frozen. Water condenses as temperature drops until 4 degrees Celsius. Past 4 degrees Celsius, the hydrogen bonds that hold water together expand, causing water to decrease in density and float.

Water is able to dissolve a wide variety of substances. Since our bodies are made mostly of water, any substances that are bad for our bodies can be dissolved in water and flushed out. Our kidneys are totally dependent on water to work. Kidneys, which filter blood, eliminate toxic substances from urine and receive water-soluble toxins from the liver for processing. Likewise, substances that are good for our bodies can be dissolved in water and absorbed. Vitamins B and C are water soluble and absorbed through the small intestine into the bloodstream. One downside of water-soluble vitamins is that they leave our bodies through urine and need to be replenished every day.

Why is this important to life?

Surface tension is a result of the cohesive forces between water molecules. Hydrogen, a positively charged atom, and oxygen, a negatively charged atom, are attracted to each other among water molecules since opposite charges attract. Because of this attraction, water is held together in droplets. Certain organisms like water striders and spiders are able to walk across the surface of water because of surface tension. Paper clips are also able to float on water because of surface tension.

Because of the density of water, we are not a frozen planet. Ice does sink as it cools until 4 degrees Celsius, but rises to the top as it expands below 4 degrees Celsius. If ice stayed at the bottom like most liquids, bodies of water would freeze from the bottom up, thus freezing them solid and killing all marine life and eventually freezing the entire planet.

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