Crystal+Growth+From+Solutions

Crystal Growth From Solutions Abstract: **Lab 14 Crystal Growth In Solutions **. **Alex Berger.** This experiment will discover the effect of different temperatures on crystal growth from solution with the hypothesis being that lower temperatures will result in numerous large crystals, while higher temperatures will result in very few and even smaller crystals. A beaker of water will be heated and a solute will be dissolved into it until the solution reaches supersaturation. 10mL of this solution will be poured into three test tubes, 30 mL total, and a piece of copper will be placed into each test tube. The copper will act as a nucleation site, allowing crystallization to occur more efficiently and easily. One tube will be put into the oven at roughly 38 degrees Celcius, one in the fridge at 4 degrees Celcius, and one at room temperature of about 25 degrees Celcius. This process will be repeated with four different solids in order to get consistent results relating to temperature and insure experimental accuracy. As the temperature is lower, the solution will hold less solute due to lower solubility existing at lower temperatures. The crystal growth rate will be affected by the evaporation of water as well. Almost all the solutions had crystallization occur, with sodium thiosulfate being the only one to fail to crystallize, most likely due to too little solute being dissolved. The results in the oven tended to be large, more well defined and harder crystals than those in the fridge, which were moist, relatively small and numerous. The room temperature results fell in between the two as an intermediate. The experiment did not fully support the hypothesis as the oven had relatively large crystals, but the fridge was still more numerous and relatively small. Key Words: Solubility, Supersaturation, Crystallization, Nucleation, Crystal Growth, Evaporation, Temperature, Size, Amount

Results: · clear colorless flat crystals · Crystals on fishing wire out of solution · small crystals || · No crystals in solution · Flat clear colorless crystals · On test tube walls above solution · Smaller and fewer than fridge results || · No visible results || · Many fine crystals held together · No liquid visible · Densely Packed || · White very moist solid · Less densely packed than refrigerator sample · Very fine crystals · No liquid visible || · Large white semi-transparent crystals · Larger crystals on top · Very solid and hard relative to other results · Lots of small crystals going up the sides of the test tube || · small white fine crystals · moist, easily broken apart || · clear colorless hard solids on bottom · Large crystals · Dense || · No crystals in solution · Very small crystals on the walls of the test tube · Clear colorless crystals || · Fine crystals · Large amount of crystals · Easily broken apart || · Slightly larger yellow crystals · Easily broken apart, yet a little more difficult than the refrigerator results · About the same ratio of crystals to liquid || · Larger crystals than room temperature results · Dark orange copper color · Harder than the fridge and room temperature results to break apart group of crystals · About the same ratio of crystals to liquid, with perhaps a little less liquid || From Left to Right: Washing Soda, Epsum Salt, Sodium Thiosulfate
 * **Compound** || **Refrigerator Results (3-6 degrees Celsius)** || **Room Temperature Results (22-25 degrees Celsius)** || **Oven Results (36-40 degrees Celsius)** ||
 * **Sodium thiosulfate** || · No crystals in solution
 * **Epsom salt** || · White moist solid
 * **Washing Soda** || · No visible water
 * **Potassium ferrocyanide** || · Many small yellow crystals

From left to right: Refrigerator, Room Temperature, Oven

Journal Article: This journal articulates how knowledge of the properties of nucleation and seeding has allowed humans to exert greater influence on the environment in which we live, more specifically in terms of cloud seeding which causes precipitation. Rainfall occurs in clouds when water particulates adhere to nucleation sites and once these rain particles reach a certain mass, they begin to fall. The premise behind cloud seeding is that the addition of more nucleation sites, or seeds, will allow for ice crystallization to occur at a more efficient rate than normal. The article goes on to say that clouds do not produce precipitation in the most efficient manner possible, and that by intentionally seeding the clouds, nations can achieve a more efficient rainfall or snowfall. The substance used as a nucleation site is silver iodide because it has a crystalline structure similar to ice. The molecular level structure is so close to that of ice, that ice tends to bond to it, thus making it extremely suitable for implementation in clouds. The possible downsides of using silver iodide have been questioned, and the harmful effects are relatively unknown as it has not been used in large amounts before. The fact exists however that the existence of these particles in the atmosphere would be on a much smaller scale than that of greenhouse gasses emitted from burning fossil fuels, which the journal states would mean a less harmful effect. This new development is significant because it allows countries help alleviate regions suffering droughts by allowing these regions to cultivate precipitation efficiently when there are clouds, and to store this water for times of need. A ten percent increase in precipitation could lead to almost 50,000 acre-feet of water in reservoirs, which would go a long way in improving conditions for these regions.