Water

Electric charge distribution

Oxygen: has partial negative charge, is electromotive (very good at getting and hanging onto electrons) Hydrogen has partial positive charge. Electrons distributed within water molecule.

Water is sticky

Water can stick to itself and other things. When it sticks to itself, it is called cohesion. It is called adhesion when water sticks to something else.

Cohesion

Attraction between molecules of the same substance

Three states of matter

Gas, Liquid, or Solid

Molecular symbol

H20

Capillary action

In a small tube, water will form a small column because it can climb up the tube. In a tube with a smaller diameter, the water can climb higher. In trees or other plants with a vascular system, there are many tubes with a very small diameter. Water, through capillary action, will climb really high in the tubes to keep the whole plant hydrated properly. In some trees, this water can travel over 100 meters up.

Density

It is a measure of how much stuff there is inside a specific volume or area. So, on the left side of the slide, you can see there is a square with one water molecule. That is a density of one molecule per square. The square on the right has a density of 4 molecules per square.

Water can dissolve other compounds

The oxygen end of the water will be attracted to the positive parts of the new compound and the hydrogen end of the water will be attracted to the negative end of the new compound. If these attractions are greater than water's attraction to itself, it might pull the new compound apart. When water molecules surround ions of this new compound they reduce the ability of that compound to stick together. Eventually, it will break up and become dissolved. Many small molecules that organisms need to survive are dissolved this way. Water is important to life because it can dissolve a great number of compounds and can thus allow reactions to happen, for example, in our blood. Non-polar molecules, like many fats, do not dissolve readily in water because they don't interact with water in this way.

Shared electrons do not hang out around each atom equally

They hang out more with the oxygen atom than they do with the hydrogen atoms. This creates an overall unequally distributed charge for the whole molecule. Water molecules thus have a partially negative side near the oxygen, and a partially positive side, near each hydrogen. We call this type of molecule a polar molecule. Because the hydrogen ion carries a +1 charge and the OH-anion carries a -1 charge, we know that a water molecule will have a neutral charge overall. The polarity results from the uneven distribution of the charges.

Partially positive hydrogen atoms stay close to partially negative oxygen atoms

This attraction is due to the interaction of the positive and negative charges and is called a hydrogen bond. While not to be confused with true bonds, such as ionic and covalent, there is an attraction that generally keeps the molecules arranged this way. It is important to know that these bonds break and form again continually as the water molecules move around.

Regulator of temperature

This works at a large scale for the entire planet as well as smaller scales. Water is able to effectively mitigate drastic changes in temperature due to what we call its high specific heat. A high specific heat basically means it is hard to get water to change temperature, either up or down. This is due to the hydrogen bonding. With water, if you add energy, it doesn't go immediately to make the water molecules zip around faster, It will first go toward breaking up the very numerous hydrogen bonds. Organisms typically cannot handle drastic, rapid changes in temperatures very well and the high heat capacity of water helps control how fast temperatures in living organisms can change.

High heat capacity

Water's high heat capacity helps life on Earth by curbing global temperature fluctuations. This is due, in part, to the presence of vast oceans and water vapor in the atmosphere, both of which retain and circulate energy. By capturing and moving energy around the world by currents, the water in the ocean and in the atmosphere both help the Earth warm more evenly. Water's high heat capacity also explains, in part, how, on a smaller scale, islands experience relatively lower temperature variation than areas of land far away from water. Nearby water acts as a kind of insulator from drastic temperature changes by releasing stored heat at night and absorbing less heat than the land during the day.

Ice floats

When we heat molecules, they move around more and, when we cool them, they move around less. As molecules move around more, the substance they make up will because less dense. As they move around less, the substance will become denser. Water also behaves this way but something interesting happens as water is cooled below 4 degrees Celsius. As the water cools to about 4 degrees Celsius, it reaches its most dense form. Then, as the water cools BELOW 4 degrees Celsius, the hydrogen bonds that normally break and reform a lot become much more stable. At zero degrees, the molecules and bonds form a three-dimensional lattice structure that has a relatively regular, hexagonal motif. Now, because the molecules are held apart by these bonds, they can't get too close. In liquid water, the molecules can bump into each other and break and reform hydrogen bonds but, in ice, they stay a little further apart, on average, and the bonds are also much more stable. Since the average distance between the molecules is greater in ice than in liquid water, the density becomes lower than that of any surrounding liquid water. Because of that density difference, the ice floats.