Before class on Wednesday, Dec. 14,
- please watch the 3 videos below (14 min, 7 min., 1 more to come)
- and take notes (note packet was handed out in class on Friday. Titled: State of Matter and Phase Changes).
- and make a comment.
chemistry matters
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chemistry matters 
Intermolecular forces strongly help to determine whether a substance is a solid, a liquid, or a gas. Depending on the phase change, depends on whether the forces will increase or decrease.Dipole- Dipole forces are forces experienced between polar molecules. They are mainly weak forces. London Dispersion forces arise between non polar molecules. These forces can induce temporary dipoles. Hydrogen bonding occurs between H atoms and highly electronegative central atoms. Mass and shape can help to determine the relative force of these attractions.
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In these videos I learned about intermolecular forces and how they affect properties. Hydrogen bonding is a type of dipole-dipole attraction that is especially strong. Hydrogen bonds occur when hydrogen is bonded to nitrogen, fluorine, or oxygen (very electronegative elements). Viscosity can be thought of as how thick something is, but is really a measure of how resistant liquid is to flow. It is related to how easily molecules move past each other. Molecules with stronger IMFs have more viscosity. Surface tension increases with stronger IMFs as well. IMFs can cause cohesion (where molecules are attracted to similar molecules) and adhesion (where molecules are attracted to a surface). Volatile liquids evaporate easily and have a high vapor pressure. Vapor pressure is the pressure that occurs when the same number of molecules escape a liquid as molecules that are drawn back to the liquid.
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In these videos I learned how intermolecular forces (IMF) can be used to determine multiple molecule properties such as boiling point and vapor pressure. The higher the IMF, the higher the boiling point. The higher the vapor pressure or volatility (liquids with high vapor pressure) means lower the IMF. Vapor pressure is the amount of pressure gas puts on a liquid which explains the space of a container of liquid. When heating up the liquid, it will gain energy. When the liquid gains enough energy to equal the amount of vapor this will be the boiling point of water and a phase change of liquid to gas will occur.
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In this video, I learned about Dipole-Dipole interactions, Hydrogen bonding, and Ion-Dipole interactions. I also learned about the different ways that inter-molecular forces affect physical properties. For example, stronger IMF means thicker liquid, lower volatility, and lower vapor pressure. I also learned about cohesion and adhesion in which shows how IMF has an effect on how the liquid interact with surfaces tension.
Question: Does stronger IMF mean more surface tension?
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Answer to Vy: Yes Vy, higher IMF means more surface tension.
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