What Are the Properties of Water? - Unique Properties that Support Life on Earth

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  • 0:00 What is Water?
  • 1:23 Water's High Specific…
  • 2:53 Water's Density Makes…
  • 4:13 Water Is a Polar Solvent
  • 4:52 Water Supports Life
  • 5:44 Lesson Summary
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Lesson Transcript
Instructor: Sarah Friedl

Sarah has two Master's, one in Zoology and one in GIS, a Bachelor's in Biology, and has taught college level Physical Science and Biology.

In this video lesson you will learn about water and its unique properties. You will also develop an understanding of how these properties make life as we know it possible.

What is Water?

You probably know that you can't survive more than a few days without water, but do you know why? Water has a number of unique properties that not only make it essential to survival, but also make life possible in the first place. To better understand water, we need to know just what water is. The chemical formula for water is H20, which means that it is made up of 2 hydrogens and 1 oxygen. These different parts of the molecule are held together by covalent bonds. Connecting water molecules to each other hydrogen bonds and these unique bonds are what make water so special.

The hydrogen bonds in water make the molecules cohesive, which means they stick together really well. The cohesion of water is much stronger than most other liquids, and this is very important. For example, water and nutrients can be transported from tree roots to other parts of the plant with cohesion.

Water also has a lot of surface tension because of its hydrogen bonds. If you look very closely at a droplet of water, it almost looks like it's coated with plastic because it holds together so well. You can see the surface tension in action if you put drops of water on a penny until a small mound forms. The reason the water doesn't spill over the edge of the coin is from the water's surface tension.

Water Has a High Specific Heat Capacity

Why do coastal areas tend to have more consistent temperatures throughout the year while areas that are farther inland have more extreme highs and lows? This is due to water's high specific heat capacity. Specific heat capacity is the resistance to temperature change. It takes a lot of energy to change the temperature of water because it takes a lot of energy to break the hydrogen bonds. Water absorbs and stores a large amount of heat from the sun and, as it cools, it releases this heat into the air that travels onto land. So in winter, when the air is colder than the water, the air literally picks up the water's heat as it passes over it onto land and warms it. Likewise, in the summer when the air is hotter than the water, the air cools off as it travels past the ocean to land and cools the shore. This is what helps keep moderate temperatures in coastal regions throughout the year.

Water's high specific heat capacity also keeps ocean temperatures fairly moderate, which is important to marine life because they can only survive within a certain range of temperatures. It also helps moderate your body temperature because you are mostly water. When you get too hot, your body cools down by releasing water through pores in your skin. This heat from your sweat, which is mostly water, is removed by the air much like the heat from the ocean along the coast. As the heat is removed, you become cooler, and this process is called evaporative cooling.

Water's Density Makes Life Possible

We can find water on Earth in three different forms: solid, liquid and gas. Most things become more dense when they cool because their molecules are condensing together, and become less dense when they heat up because their molecules are moving farther apart from each other. Do you think water behaves like this? It sure doesn't! When water becomes cooler and freezes, it actually expands, because each water molecule connects to its neighboring water molecules with hydrogen bonds. This creates a crystal-shaped structure between the molecules, which spreads them out and increases the volume. And since this makes ice less dense, this means it floats on top of water.

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