Discussing Issues Relating to Oceanography - Assignment Example

Oceanography Why is the latent heat of vaporization so much greater than the latent heat of melting? The latent heat of vaporization is much greater than the latent heat of melting or latent heat of fusion. This can be explained on the basis of molecular behavior. During melting, the temperature of a substance remains constant and so the kinetic energy of the molecules is fixed. The energy supplied in the form of heat is used to move the molecules away from one another. Therefore, the potential energy of the molecules is increased due to their to and fro motion, and the energy required for this motion is called latent heat of fusion or latent heat of melting. A substance melts when its molecules move apart and have a “wider range” of motion than is possible in solid state (Yong and Wai 197). During boiling or conversion from liquid to vapor state, energy is not only required for overcoming the attractive forces between molecules but also for expanding the vapor against the atmospheric pressure. The energy required for this process is called latent heat of vaporization. In this case, too, the kinetic energy of the molecules remains constant. Latent heat of melting only breaks down a few bonds between molecules while latent heat of fusion breaks down all the bonds. Moreover, during vaporization, the molecules are reorganized more vigorously than during melting. Therefore, the latent heat of vaporization is greater than the latent heat of fusion. For example, the latent heat of melting of ice (6.0×103 Jmol-1) is only 15% of the latent heat of vaporization (Adkins 79). 2) Why are the freezing and boiling points of water higher than would be expected for a compound of its molecular makeup? This is because of the strong intermolecular forces between water molecules. Water molecules are polar because of charge separation between the oxygen and hydrogen atoms, where oxygen atoms are partially negative and hydrogen atoms are partially positive. Because of the presence of positive and negative poles, each water molecule bonds with other water molecules. This leads to strong intermolecular hydrogen bonding. The boiling point and the freezing/melting point of water are higher than that of other compounds of similar makeup, such as H2S, H2Te and H2Se, because larger amounts of heat are required to overcome the strong hydrogen bonds in water compared to other compounds where hydrogen bonds are absent. Thus, the freezing point of water (which is equal to the melting point) is 100ºC higher than expected and the boiling point is 200ºC higher than expected (Spencer, Bodner, and Rickard 333). 3) Discuss how the dipolar nature of the water molecule contributes to a. its universal solvent nature A water molecule is a dipole, i.e. it has a positive pole and a negative pole. When ionic compounds are added to water, they readily break down and dissociate into their constituent positive and negative ions because the dipole nature of water pulls the two ions apart. For example, NaCl, which is an ionic compound, readily dissociates into Na+ and Cl- when added to water. Since most ionic compounds easily dissolve in water, it is known as a universal solvent. b. the formation of hydrogen bond. A water molecule is made up of an oxygen atom, which is bonded to two other hydrogen atoms. Since oxygen is more electronegative than hydrogen, oxygen acquires a partially negative charge by pulling the shared pair of electrons towards itself, while hydrogen acquires a partial positive charge. This gives rise to a dipole. Hydrogen bonding occurs when the positively charged hydrogen atom of one water molecule attracts the negatively charged oxygen atom of another water molecule. Therefore, the dipolar nature of water molecules contributes to the formation of hydrogen bonds between them. 4) Describe how excess heat absorbed by Earths low-latitude regions is transferred to heat-deficient higher latitudes through a process that uses waters latent heat of vaporization. Latent heat is the heat absorbed or released when a state of matter changes from one form to another. The latent heat of water required when it changes from liquid to vapor state is called the heat of vaporization. The heat of vaporization of water (latent heat) is very high. Oceans lose large amounts of heat due to vaporization of water. It is estimated that on average, the total heat loss by evaporation is 78 Watts/sqm (Gordon). The water vapor formed due to vaporization is transferred from the oceans to the atmosphere, where it condenses into water droplets, thereby forming clouds. In this process, the latent heat of vaporization is transferred from the oceans to atmosphere. Therefore, there is heat exchange between the ocean and the atmosphere owing to the latent heat of vaporization of water. Since the oceans at the higher latitudes away from the equator lose heat and those at the lower latitudes closer to the equator gain heat, high latitude regions are heat-deficit and low latitude regions have excess heat. In a steady state condition, heat is transferred from warmer to cooler areas. Ocean currents thus carry heat from areas having excess heat to heat-deficit areas. Therefore, heat is transported from the tropical regions to the Polar Regions. 5) How does the heat capacity of water compare with that of other substances? Describe the effect this has on climate. The heat capacity of water is 1 calorie/gm/ºC (Allaby 268). This is higher than most other known substances. This indicates that water can absorb large amounts of heat while changing its temperature only slightly. This characteristic of water has wide-ranging implications on climate. Because of the high heat capacity of water, seas and other large water bodies heat up very slowly during hot climates. Moreover, during winter, water bodies cool very slowly, but release large amounts of heat in the process. Therefore, oceans and large water bodies act as heat stores, absorbing large amounts of heat in during summers and releasing the stored heat during winters. References Adkins, Clement John. An introduction to thermal physics. Cambridge: Cambridge University Press, 1987. Web. 30 Sept. 2011. Allaby, Michael. Encyclopedia of Weather and Climate: A-L. New York: Infobase Publishing, 2002. Web. 30 Sept. 2011. Gordon, Arnold. The Climate System. Eesc.columbia.edu, 2004. Web. 30 Sept. 2011. Spencer, James, George M. Bodner and Lyman H. Rickard. Chemistry: Structure and Dynamics. Massachusetts: John Wiley and Sons, 2010. Web. 30 Sept. 2011. Yong, Loo Wan and Loo Kwok Wai. Physics insights: O level. Singapore: Pearson Education South Asia, 2007. Web. 30 Sept. 2011. Read More