Tuesday, September 21, 2010

The Properties of Water

Water is one of the most vital elements on the planet. There are many reasons that water is so vital, including properties that make water so special:

1) Universal Solvent: This property proves how vital water is because almost anything can dissolve into it. This is possible because when water is formed, the bond (between hydrogen and oxygen) is called a polar covalent bond. This bond is when electrons need to bond with another to fill their electron shells, but the electrons don't share equally. Because of this, one side of the water bond is slightly negative, and the other is positive, as shown in this picture link. Because this bond is both negative and positive, atoms that both have a negative charge and positive charge are able to dissolve into it, thus making it possible for almost anything to dissolve into water.

2) Polarity: Polarity is when a compound of polar covalent bonds have a slightly negative side and a slightly positive side. This allows water to do many things including being a universal solvent, explained above, adhesion, cohesion, and specific heat all explained below.

3) Adhesion: Adhesion is when a substance "clings" to another substance. Adhesion happens because water, being a polar molecule, attracts both negative and positive objects. Because of this, water will cling to another object. As a result of adhesion there is capillary action. This action is, when in a narrow enough space, water will climb up the sides of the object it's clinging to. This allows plants to suck water in from the ground and reach their top, allowing them to live.

4) Cohesion: Cohesion is the exact opposite of adhesion. In cohesion, instead of sticking to other things, it sticks to itself. It sticks to itself because water is a polar covalent bond, and can form a hydrogen bond, which makes it stick to itself. One example of this is a raindrop. When falling, the drops of water stick together because of cohesion.

5) Surface Tension: Surface tention is the tightness across the surface of water. This is caused by cohesion because the water is sticking to itself, causing the surface of the water to have a tight layer that if an if this object is light enough, it will not break through the surface and be able to stand on top of it. An example is this video, and of the picture below.

6) Specific Heat: Specific heat is the amount of energy needed to raise one gram of something up 1° Celsius. The reason this is special towards water is because it has a high specific heat. This is because hydrogen bonds (Polar Bonds that weakly bond to other polar bonds) when bonded together have a higher Specific heat than regular bonds, as shown in this video.
                                                         Specific Heat Explained

This property of water is essential to organisms because it keeps us from overheating and cooling because it takes so much energy to heat up/cool down water.

7) Density: Density is described as the amount of mass in a given space. With that said, it is usual for liquid substances to be less-dense than their solid state because the solid molecules are more condensed into a place than liquids. Water is so cool because it does the exact opposite. When water is in a solid state, it will actually float on top of liquid water. It does this because in liquid water, the molecules are really close together and when they change forms into solids they spread out and form a lattice formation. As shown in these pictures, the left being a solid formation, and the right being liquid.

8) pH (acidity): A pH scale is to test the acidity in a given substance. The reason that substances have different pH levels is due to ionization. Ionization is the conversion of a non-ionic compound into an ion. An ion atom is an atom with ranging numbers of electrons, and a non-ionic atom is when the number of electrons and protons are equal. When ionization happens, a bonded molecule (H2O) breaks apart, and one element takes another element's electron, causing one element to be negative (OH-) and one to be positive (H+). In water, for example, there are an equal amount of positive and negative atoms, which means that it has a pH of 7, or neutral. This is because if, for some reason, a substance has an unequal balance of negative and positive elements, the acidity will shift to more acidic or more basic.

*** For a video on Cohesion, Adhesion, and Surface Temperature, see here.


  1. Hey Megan!
    I really like your blog post! The pictures and videos are great! I particularly liked the screen jar video. I also liked how you connected the definition of polarity to other properties, and your description of adhesion.


  2. Megan,
    This is a really awesome blog post! Its nice and organized which makes it very easy to understand.

  3. Post is written in a great "approachable" voice. Be careful when explaining polar covalent bonds. The bond itself is not negative and positive. The result of the bond, however, is a molecule that is slightly positive and slightly negative. Your incorporation of multimedia really compliments the text and enhances your explanations. Great job!