What is the Difference Between Polar and Nonpolar Molecules and How do they Affect Molecular Interactions PDF

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Professor: Tara Carpenter
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What is the Difference Between Polar and Nonpolar Molecules and How do they Affect Molecular Interactions? Dear Chloe, There are several different ways in which molecules can be chemically bonded together. One type of chemical bond is a covalent bond, which can be further divided into two classes: polar covalent bonds and nonpolar covalent bond. These types of covalent bonds both involve the sharing of electrons between molecules. The distinguishing difference, however, is that in polar bonds, electrons are distributed unequally, whereas in nonpolar bonds, electrons are shared equally. As for how the different types of bonds influence molecular interactions, polar and nonpolar molecules tend to avoid interacting with each other. In other words, when placed together, a polar molecule and a nonpolar molecule will not interact and instead repel each other. The reason for polarity is due to the uneven distribution of electrons in a molecule containing atoms with different electronegativities. This results in a shift in electron density, which forms dipoles and results in an overall dipole moment– “a quantitative measure of the polarity of a bond”– value unequal to zero (Burdge & Overby, 2018, p. 218). Additionally, when a molecule is polar, its atoms will have partial charges (the more electronegative atoms will have negative partial charges because they have more “pull” on electrons). These partial charges allow the partial positive and partial negative regions of the molecule to interact with other polar molecules, because opposite partial charges attract each other. Often, polar molecules are referred to as hydrophilic because they readily interact with polar water molecules. In a nonpolar molecule, however, these dipole moments are “equal in magnitude and opposite in sign”, causing them to cancel out and yield a net dipole moment of zero (Burdge & Overby, 2018, p. 256). Since nonpolar molecules do not possess partial charges, they do not interact with polar

molecules, hence why they are often called hydrophobic (aka they do not readily dissolve through interacting with water molecules). Why does this pertain to you? Many, everyday products that you use rely on the polar and nonpolar properties of certain molecules in order to function. For instance, dish soap relies on the properties of its molecules to be able to effectively clean food debris off kitchenware. The reason why soap is effective is because its molecules possess both polar and nonpolar regions; the polar ends interact with water and the nonpolar ends interact with nonpolar food molecules (like fats and oils). Water alone is an ineffective method of cleaning oily dishes because water is polar, and as discussed before, polar molecules and nonpolar molecules do not readily interact. However, with the addition of soap, hydrophobic interactions can occur between food molecules and the nonpolar regions of the soap molecules, subsequently breaking up the oils/fats. Understanding the polar and nonpolar properties of everyday objects will allow you to use such objects more effectively. Not only is this information useful to you, but it can be used to help others. Applying the same principles of dish soap, product manufacturers can produce better, more effective products that will be more beneficial to both them and their consumers. Besides developing effective soaps that thoroughly clean dishes and prevent bacterial growth (and therefore prevent the spread of disease-causing agents), companies can manufacture better waterproof clothing items and technology, “non-stick” kitchenware, etc., by using their knowledge of the properties of polarnonpolar molecular interactions. Enhancing these everyday objects helps to provide substantial health and economic benefits for all those involved.

Citations Burdge, J., & Overby, J. (2018). Chemistry: Atoms First (3rd ed.). New York, NY: McGraw-Hill Education....