Explain the following phenomena in terms of intermolecular forces. Determine the major type of forces between the molecules.
a) You can't clean grease off you hand with water only
b) Pancake syrup is more dense than olive oil. Please provide the structure of both in your discussion.
c)Water beads up on a newly waxed car
d)Br2 and I2 are both nonpolar compounds with London forces being the major types of forces between their molecules. Yet, Br2 is liquid and I2 is solid at room temperature.
a) When trying to clean grease off your hands with water only, you may notice that it is difficult to remove. This is due to the difference in polarity between water and grease molecules. Water is a polar molecule, meaning it has a partial positive charge on one end and a partial negative charge on the other. On the other hand, grease molecules are nonpolar, meaning they do not have a significant charge separation.
In terms of intermolecular forces, the major type of force between water molecules is hydrogen bonding. Hydrogen bonds occur when the positive end of a water molecule is attracted to the negative end of another water molecule. This leads to a strong cohesive force and contributes to the high boiling point and surface tension of water.
However, grease molecules are nonpolar and do not form hydrogen bonds. Instead, they experience London dispersion forces, which are the weakest intermolecular forces. London forces arise from temporary fluctuations in electron distribution, which create temporary dipoles in nonpolar molecules. These temporary dipoles induce similar dipoles in neighboring molecules, creating a weak attractive force.
Because water molecules cannot form strong interactions with nonpolar grease molecules, water alone is not effective at removing grease from the skin.
b) The difference in density between pancake syrup and olive oil can also be explained by their intermolecular forces and structure. Pancake syrup is typically a mixture of sugar, water, and various additives, while olive oil consists mainly of triglycerides.
In terms of intermolecular forces, the major type of force between the molecules in both pancake syrup and olive oil is the dispersion force. Dispersion forces arise from temporary fluctuations in electron distribution, leading to temporary dipoles in molecules. The strength of these forces depends on the size and shape of the molecules involved.
Pancake syrup, being a mixture of sugar, water, and additives, contains molecules with more varied structures and sizes compared to olive oil. The presence of sugars and other larger additives in pancake syrup increases the overall molecular size and complexity, resulting in stronger dispersion forces between the molecules. As a result, pancake syrup is more dense than olive oil.
c) The phenomenon of water beading up on a newly waxed car can be attributed to the intermolecular forces between water molecules and the wax-coated surface of the car.
In terms of intermolecular forces, the major type of force between water molecules is hydrogen bonding. Water molecules are highly polar, with the oxygen atom having a partial negative charge and the hydrogen atoms having partial positive charges. These partial charges allow water molecules to form hydrogen bonds with other water molecules, resulting in a cohesive force.
When water comes into contact with a wax-coated car surface, the wax molecules form a nonpolar barrier. Since water is polar and wax is nonpolar, there is a lack of intermolecular attractions between water and the wax. As a result, water molecules tend to minimize their contact with the wax surface, forming spherical droplets or beads that sit on top of the hydrophobic wax layer.
d) Both Br2 (bromine gas) and I2 (iodine) are nonpolar compounds and exhibit London dispersion forces as the major type of forces between their molecules.
In terms of intermolecular forces, London dispersion forces arise from temporary fluctuations in electron distribution, creating temporary dipoles in nonpolar molecules. These temporary dipoles induce similar dipoles in neighboring molecules, resulting in weak attractive forces.
The reason Br2 is a liquid and I2 is a solid at room temperature, despite both being nonpolar compounds, can be explained by the difference in molecular size and shape. Iodine molecules (I2) have a larger molecular size compared to bromine molecules (Br2). Larger molecules have a greater number of electrons, leading to stronger London dispersion forces between the molecules.
The stronger intermolecular forces in I2 contribute to a higher melting point, making iodine a solid at room temperature. On the other hand, bromine (Br2) with smaller molecules and weaker London forces is a liquid at room temperature.