Water as Polar Molecule Alex M. Schandelson The University of Montana 161: Principles of Living Systems Lab Derik Butts 10/8/23 Water as Polar Molecule Perhaps the most essential molecule for living systems, water has many unique traits that allow living systems to flourish. A low-density solid-state insulates the water beneath, allowing life to survive during extremely low temperatures (Georgios et al., 2022). Through cohesion and adhesion, water fights against gravity dozens of feet in the air to nourish plants. Water’s specific heat helps balance environments and regulate climate patterns (Emiliano et al., 2017). These properties are essential for life. Water is said to be one of the strangest substances ever studied. The properties of water are both atypical and essential. In this lab, we dive deeper into polarity, specific heat, and how life has come to depend on it. Water has a massive impact on the environment around it; therefore, we can form some hypotheses by observing water's behavior. Water has a high specific heat and is polar. Assuming this is true, we would expect water to heat up at a far lower rate than a substance without hydrogen bonds. We would also expect water to be affected by the presence of an electric field due to its polarity. Inversely, the null hypothesis would state that water does not have a high specific heat or polarity. Therefore, water would heat up at a rate similar to substances without hydrogen bonds and unaffected by electric fields. This would mean that the life-sustaining properties we have attributed to hydrogen bonds and water’s polarity would be due to some other mechanism. Materials and Methods The lab was subdivided into multiple stations, each designed to test a different characteristic of water. The first station tested the specific heat of water against other substances without hydrogen bonds. The rationale is that the heat from the hot plate breaks the hydrogen bonds and expends that energy. This allows water to absorb large amounts of energy with little rise in temperature increase. The second station was dedicated to observing an electric field's effect on polar and nonpolar molecules. The first station tested the specific heat of water and compared it to other substances with varying degrees of hydrogen bonding ability. First, 50 milliliters of water, ethanol, and vegetable oil were carefully measured and poured into separate Erlenmeyer flasks. Custom rubber stoppers connected to a thermocouple were placed on each flask. Once each Erlenmeyer flask was outfitted with a sensor, all three flasks were placed on the same hot plate. The temperature of all three flasks was recorded every minute for five minutes. The second station observed the polarity of water and how an electric field affects it. A burette was filled with water. A basin was placed underneath it to catch the water. Then, a glass rod was rubbed with a rabbit pelt to charge the rod. Once the rod had a charge, the stopper was adjusted to allow a steady stream of water flow. The charged glass rod was moved close to the stream of water. A second test was performed with a balloon instead of the glass rod. Paraffin oil was placed in the burette with the same setup, and the test was repeated. The stopper was adjusted to allow a steady stream of oil to fall. The charged glass rod was brought near the oil. A second test was performed with the balloon instead of the glass rod. Results All of our findings can be attributed to the structure of water. The first test that examined specific heat in comparison to ethanol and vegetable oil illustrated the ability of hydrogen bonds to absorb energy without rapid changes in temperature. Graph 1 illustrates the resistivity of water to thermal energy. Temperature vs. Time 120 Temp (C) 100 80 60 40 20 0 0 1 2 3 4 5 Time (min) T1: Oil T2: H2O T3: ETOH Graph 1: Temperature vs. Time Graph. Each substance started at relatively similar temperatures. However, the substances hydrogen bonds increased their temperature Eachwithout substance increased its temperature; however, waterthe hadmost. the least percent change of the three substances. Oil had a 203% change, ethanol had a 164% change, and water had a 147% change. The second test observed water polarity and how that is affected in an electric field. Figure 1. illustrates how water aligns itself in the presence of electric fields. Figure 1. Caption: The Polarity of Water and Electric Fields. Even in electric fields, opposites attract. (Granger, 2002) As the water fell from the burette, it changed its trajectory in accordance with the shape of the electric field. The electric field did not affect the test with paraffin oil, a substance without hydrogen bonds. This result was expected and aligns with our current understanding of polarity. Substances that share electrons equally are considered to be net-neutral molecules. This means that, as a whole, the charges are balanced and, therefore, unaffected by electric fields. Discussion During these experiments, we analyzed water's properties, focusing on its specific heat capacity and behavior as a polar molecule. Most of water's properties can be attributed to its polar nature. For instance, the ability of water to resist temperature changes results from the energy-absorbing properties of hydrogen bonds (Sokhan et al., 2015). Furthermore, the presence of electric fields affects polar molecules like water, as observed in our second experiment. Both of our hypotheses were validated, leading to the rejection of the null hypothesis. We have concluded that these phenomena are attributed to water's polarity. While it may appear that these findings are of limited significance, their implications are substantial. Many of the life-sustaining properties water exhibits can be traced back to its polarity. These properties, including cohesion, adhesion, low-density solid state, and resistance to temperature changes, play crucial roles in nourishing plant life, stabilizing climates, and fostering a habitable environment. Without these fundamental traits, life as we know it would not be sustainable. In future repetitions of these experiments, we recommend several enhancements to ensure the accuracy of results and minimize external influences. For the specific heat experiment, we suggest providing each flask with its dedicated hot plate, maintaining all substances at a consistent initial temperature, and ensuring each flask remains at a constant initial temperature throughout the experiment. These measures will help standardize thermal energy input and reduce potential sources of mathematical error. External influences may skew data and lead to inaccurate conclusions. References Emiliano Brini, Christopher J. Fennell, Marivi Fernandez-Serra, Barbara Hribar-Lee, Miha Lukšič, and Ken A. Dill Chemical Reviews 2017 117 (19), 12385-12414 DOI: 10.1021/acs.chemrev.7b00259 Georgios M. Kontogeorgis, Andrew Holster, Nomiki Kottaki, Evangelos Tsochantaris, Frederik Topsøe, Jesper Poulsen, Michael Bache, Xiaodong Liang, Nikolaj Sorgenfrei Blom, Johan Kronholm, Water structure, properties and some applications – A review, Chemical Thermodynamics and Thermal Analysis, Volume 6, 2022, 100053, ISSN 2667-3126, https://doi.org/10.1016/j.ctta.2022.100053. Sokhan, V. P., Jones, A. P., Cipcigan, F. S., Crain, J., & Martyna, G. J. (2015). Signature properties of water: Their molecular electronic origins. Proceedings of the National Academy of Sciences of the United States of America, 112(20), 6341–6346. https://doi.org/10.1073/pnas.1418982112 Granger, J. (2002). Water in an Electric Field. The Chemistry of Water, Structure Means Function. Retrieved 2023, from http://witcombe.sbc.edu/water/chemistrystructure.html.
