IMF's and fun

This week in chemistry we learned about forces of attractions. Some of the forces included intramolecular forces, the attractive forces that hold atoms together within a molecule, and intermolecular forces, the attractive forces that hold identical molecules together between molecules. Also we learned about the three types of IMF's. The weakest IMF is called dispersion forces (AKA London forces). These type of forces are formed when two molecules become close and the e- cloud of one repel the other e-cloud. The second type of force is called dipole-dipole forces. These forces are formed when molecules orient themselves so the the slightly negative end of one molecule is attracted to the slightly positive end of the nearby molecule. The last and strongest bond is called a hydrogen bond. A hydrogen bond is formed when electronegetive atoms cause a large partial positive charge on the hydrogen atom. We also learned about phase changes. Phase changes require energy to happen. Phase changes that absorb energy make the particles move faster and the IMF's duplicate causing melting and evaporating. Phase change that remove energy make the particles move slower and strengthened the IMF's causing freezing and condensation. Lastly we learned about the phase diagram. The temperature and pressure shown on the graph determine the phase of a substance and have opposite effects. Higher temperature causes more liquid to evaporate but higher pressure causes vapor to condense.  

This week we also did multiple labs that related to what we learned this week. One lab we did was the drops on a penny. We took water first then ethanol and dropped as many drops on the head side of a penny as we could until the water/ethanol spilled over. By doing this lab we learned that water had a stronger intermolecule force because we could as more drops of water to the head of the penny than ethanol drops.  

Another lab we did was the CO2 bubble, which was the best lab. In this lab we mixed water and dry ice to create a gas, then we took a strip of cloth and soaked it in soapy water. After this we took the strip of cloth and ran it over the bowl containg the water and dry ice. After a few trys a bubble formed on the bowl causing the bubble to expand. We learned after that the attractrion that holds the molecules together of CO2  double bonds. 

Link:http://chemed.chem.purdue.edu/genchem/topicreview/bp/intermol/intermol.html#force