Last week’s readings were all about the states of matter. Whether a substance takes on the form of a solid, liquid or gas all depends on both the intermolecular forces (that is, the force of attraction between molecules) as well as the intramolecular forces (the bonds that exist within each molecule). The easiest example to really understand this concept is looking at the state of water. Like every other substance, the state of matter of water is determined by the balance of kinetic energy and the intermolecular forces of attraction. As we know, the water molecule consists of a covalent bond between 2 hydrogen atoms and an oxygen atom. In fact, as the hydrogen atom caries a slight electropositive charge, and the oxygen atom has a slight electronegative charge, water is a polar molecule with an electrical dipole moment. This gives water a stronger bond and thus it requires a higher temperature to induce vaporization.
When you heat water, the molecules gain energy and start vibrating faster. Thus the kinetic energy increases, and the molecules are able to break their bonds and become a gas at the boiling point. What was really interesting as well, and something that I never realized was that pressure also plays a significant role – at higher altitudes there is less pressure and water can reach its boiling point at a lower temperature. In fact, if the altitude is high enough water can even boil at room temperature!
I think that the relationship between pressure and boiling/melting points is interesting. It would be interesting to explore this relationship with other substances and see how low the pressure needs to be in order to induce vaporization at room temperatures.