The Wonders of Water

Why Water? 

1.) Water is an important molecular compound that supports life on Earth.

2.) Properties of Water explain hydrophobicity and boiling point.

                                polar molecule     water molecule     H2O Lewis dot

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Chemistry explains the properties of water. First, water is a polar molecule. The polar molecule has two partial positive Hydrogen molecules and one partial negative Oxygen molecule, creating a dipole moment cause by the differences in electronegativity among the molecules. Due to polarity, water molecules are a universal solvent with the ability to dissolve other polar molecules in solution by attracting and separating ions from other substances. Second, water has Hydrogen bonds. Hydrogen bonds are the strongest bonds formed between molecules. Water’s Hydrogen bonding contributes to its polarity. The Hydrogen bonding also allows water to have a solid form less dense than a liquid form, a high boiling point of 100.0 degrees Celsius, and a high heat capacity. Finally, water has amphoteric properties. Meaning, water molecules are able to create both an acid with H+ ions and a base with OH- ions when polar bonds are broken. We can extend these polar properties of water to explain hydrophobicity and boiling point.

Water Repelling Chemistry!

Raincoats, car windshields, and household paints are made to repel water molecules. In order to achieve this, the surface area of a substance must be hydrophobic, ‘afraid of water.’ The hydrophobic effect occurs when non polar substances aggregate in aqueous solution to exclude water; that is, the non polar molecules will repel the polar molecules. Hydrophobic surfaces are made up of polymers, such as, polysiloxanes or polyfluorinated compounds. Many consumer products are designed with theses polymers to create hydrophobic properties. For example, raincoats are designed with Gore-Tex, a compound substance with PTFE, polytetrafluoreothylene, creating a waterproof coating on clothing. In addition, car windshield treatments are coated with Rain-X, a substance containing polysiloxenes compounds to attain hydrophobicity. Finally, some walls are coated with hydrophobic paints to repel water molecules. water repelling chemistry

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What Temperature Does Water Boil At? Boiling Point and Elevation. 

The boiling point of a substance is the temperature at which the vapor pressure of a liquid equals the pressure surrounding the liquid, and then the liquid changes into a vapor. Water, and other substances, change states once the chemical bonds are broken in the compound. Water, at sea level, has a high boiling point because it takes more energy to overcome the strong polar and strong Hydrogen bonds. At sea level, water has a boiling point of 100.0 degrees Celsius. Why does water’s boiling point change? It is true that at higher elevations water’s boiling point decreases. However, water’s boiling point varies not because of elevation, but because of atmospheric pressure and temperature. Atmospheric pressure decreases at higher elevations, and therefore the vapor pressure for water to transform into the gas phase decreases. In addition, vapor pressure will decrease at decreased temperatures as more molecules have the kinetic energy to overcome attraction with other molecules.  Lower pressures allow molecules to escape more easily as the vapor pressure required for a state change decreases. Bonds between molecules, temperature, and vapor pressure explain why water exhibits its lowest boiling point of 69.94 degrees Celsius on Mt. Everest, where the elevation is 8848m, pressure is o.33atm, and temperature is between -20 and -40 degrees Celsius. water boiling point .png

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In conclusion, understanding the chemistry, and more specifically, the polarity of water molecules develops our understanding of hydrophobicity and boiling point of H2O. We can further extend our knowledge of hydrogen bonds to explain properties of the ocean. Did you know that hydrogen bonding among water molecules creates a high heat capacity for water? Water’s high heat capacity allows the ocean to thermoregulate coastal climates. For example, the coastal city, Charleston, South Carolina has an annual high average temperature of 76.1 degrees Fahrenheit and an annual low average temperature of 55.6 degrees Fahrenheit as compared to the upstate city Columbia, South Carolina with an annual high average temperature of  75.3 degrees Fahrenheit and an annual low average temperature of 52.3 degrees Fahrenheit. The ocean will absorb heat emitted, hydrogen bonds are broken, which in turn cools the atmosphere in the summer. Furthermore, the Ocean will release heat, hydrogen bonds are formed, which in turn warms the atmosphere in the winter.

Sources: 

http://cen.acs.org/articles/94/i15/Periodic-graphics-Water-repelling-chemistry.html

What Temperature Does Water Boil At? Boiling Point & Elevation

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Chemistry Matters

Today, I discovered my own love for Chemistry! The Chemistry Matters Symposium at Centre College is an opportunity for students to share their knowledge about Chemistry. I realized that the purpose of the symposium is to explore and to help students realize how Chemistry affects nearly everything and everyone in the whole world. I report to you about how Chemistry affects the brutalities of war, the water we drink, and the oxygen we breathe.

Combating Landmines

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Landmines are often hidden under brush, dirt, and leaves making these weapons a great war tactic, but chemistry explains how the reaction makes landmines explosive and deadly. 

Landmines are a dangerous war tool. They are explosive devices placed just beneath the ground with the purpose of blowing up any person, vehicle, or animal that steps on the  and triggers the device to set off. Landmines are used as a war tactics because they are cheap, easy to improvise, kill effectively and indiscriminately, and require to upkeep. Landmines explode by setting off a Chemical reaction using trinitrotoluene (TNT) in its solid state. The Chemical equation is: 2 C7H5N3O6 –> 3N2 + 5H20 + 7CO + 7C. An explosion occurs only when weight is placed on top of the device. The pressure from the weight ignites the firing pin to cause a chemical reaction. The TNT decomposes to release a shockwave explosion of dinitrotoluene (DNT). More specifically, the boom, the explosion, is causes when Nitrogen gas molecules combine to form a strong triple bond. The exothermic bonds release a huge amount of energy and heat. Current countermeasures are being taken to remove hundreds of thousands of active landmines from current and previous war zones in Central America, South America, Western Europe, and the Middle East. Mine sweepers act as metal detectors and K-9 units sniff out DNT. How cool is it to learn about Chemistry causing a huge explosion!

The Quest For A Clean Drink

contaminated water
Chemistry helps us to remove contaminants, such as, bacteria, microbes, and arsenic which may cause serious illness or death,  from the drinking water. 

Nearly one billion people world wide do not have access to clean drinking. Their alternative is well water or ground water that is contaminated with bacteria, microbes, arsenate, and arsenite. Drinking harmful bacteria may lead to disease and the possibility of death. Drinking microbes may lead to skin cancer with the possibility of death. Drinking arsenate and arsenite, a toxic chemical, leads to immediate death. The detrimental problem of contaminated drinking water affects populations in Eastern Asia. Luckily, a team chemists has proposed three procedures for eliminating toxic arsenate and toxic arsenite from water. The first method is using buckets to make filters. The filter of the buckets contains a composite iron matrix, which filters out arsenic by means of a chemical reaction: FeOH + H2AsO4 ➞ FeOAsO3H+ H2O and FeOH + HAsO42 ➞ FeAsO42 + H2O. The toxic arsenate ions are filtered out because they are attracted to the negative hydroxide ions. The second procedure is removing arsenic with a pump. The stainless steal pump uses a substance called adsorbent alumina, a polymer, which catches arsenic as the ground water is filtered through the pump and comes out to be more safe drinking water.The chemical equation is: 4Fe2+ +O2 +10H2O➞4Fe(OH)3 +8H+. The third method is an arsenic removing powder. The powder goes through three process, known as coagulation, flocculation, and disinfection, in order to remove arsenic and kill bacteria within the water. Thanks to these newfound chemical processes, the lives of billions of people worldwide are saved from contaminated drinking water.

“Hitting The Wall” – Running A Marathon

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Dennis Kimetto set the world record for a marathon (a 26.2 mile race) at 2:02:57. Chemistry explains how his body has undergone both aerobic and anaerobic respiration in just two hours. 

A Final example of Chemistry at work is aerobic and anaerobic respiration. If you are a  runner, you have experienced both aerobic and anaerobic respiration. If you are a marathon runner, you have experienced “Hitting a Wall” when you body switches from aerobic to anaerobic respiration.  Aerobic respiration is explained by the chemical formula, C6H12O6 + 6O2 –> 6CO2 + 6H2O + energy. Everyone, not just runners, undergoes aerobic respiration when your body burns the stored glucose and glycogen in your body to create energy. On average, a person can store up to 2,000 calories of glycogen. A runner therefore, can run 20 miles, burning on average 100 calories a mile, before glycogen stores are depleted in one body and before aerobic respiration ceases. Marathon runners undergo anaerobic respiration, when they hit mile twenty. During Anaerobic respiration, your body uses the fat storage to create energy. A runner will grow extremely tired at this point in the race because they must breathe in four times as much oxygen to create energy through anaerobic respiration. To resolve this problem, runners carload, consume in race carbohydrates, and elite runners are able to store increased levels of oxygen in their lungs with time and training.

In conclusion, giving a chemistry matters talk heightened my interest in the field of Chemistry and improved my own knowledge and how to give an effective, informative, and captivating presentation. From the other presenters I learned to be engaging by showing excitement and personal connection with my topic of choice. I also learned how to be time effective by giving a five minute presentation, but to be precise and thorough in explaining the topic and its significance.