Molecular Attraction & Phases of Water

Unlike most substances, water is commonly found in all its phases (solid, liquid, and gas) on earth. The unique properties of each of the phases also contribute to many aspects of life. For instance, the maximum density of water occurs at about 4.0 Celsius (Density = 0.9998 g/mL), and water is less dense upon freezing (Density of Ice= 0.939 g/mL), expanding approximately 9 %. This property is highly unusual for solids, and as a result ice floats in both pure water and sea water, which allows organisms to survive in partially frozen lakes, rivers and oceans.

Other Physical/Chemical Properties of Water:

  • Water has a very high surface tension, so water forms drops (the molecules tend to stick together). This stickiness also leads to capillary action such as water “climbing” a capillary tube. Capillary action is critical to plant growth.
  • Water has a large specific heat. That is, liquid water can absorb a relatively large amount of heat before it boil (vaporizes). This effect help regulate the earth’s temperature, especially in areas close to oceans, or even around Flathead Lake where many cherries are grown.
  • Purified water (often distilled or de-ionized [DI]) has a neutral pH, i.e. pH = 7.00, which mean that it is neither acidic or basic.

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The MSP project is funded by an ESEA, Title II Part B Mathematics and Science Partnership Grant through the Montana Office of Public Instruction. MSP was developed by the Clark Fork Watershed Education Program and faculty from Montana Tech of The University of Montana and Montana State University, with support from other Montana University System Faculty.