The Effect of Salinity on the Height an Egg Floats • Presented by: Amber Barton, Anelize Core, Will Gow, Bri9ney Kerwin and Molly Mueller Introduc?on • The project that our group was assigned to was to figure out whether an egg can float in saltwater or not. • The purpose of this experiment is to relate the findings to Global Warming in a way that children can understand what is happening to our oceans. Introduc?on • Global warming is the increase in the average temperature of the Earth's near-­‐surface air and oceans, and its projected conGnuaGon. Introduc?on • We conducted this experiment because we wanted to know whether salt and warm water can change the buoyancy of a specific object: in this case, an egg. We hoped to learn the exact measurement of salt that it takes for an egg to float in water. We wanted to see how much of a difference the egg floats when its surroundings are changed, much like global warming. Introduc?on • This experiment allows us to change the independent variable, like the amount of salt in the water, to observe how the dependent variable changes. • Our hypothesis is that aJer adding 45ml of salt to the 750ml of water, our egg would float. We have set up our experiment to find out just how much salt it takes to make the egg float. Materials • 1 uncooked egg in the shell • table salt • warm water • metric ruler • plas?c container • 50ml beaker • 1000ml beaker Methods • Once the materials were gathered we filled the 1000ml beaker with warm water to the 750ml mark and no salt was added. The egg was then placed inside the beaker along with a ruler to measure the height from the boPom of the beaker to the top part of the egg. This measurement was taken two addiGonal Gmes for a total of three measurements. • AJer the measurements were taken the egg was then taken out of the beaker and placed in a plasGc container. Using a 50ml beaker we measured 15ml of salt and then added it to the water. Once the salt was added we sGrred it unGl dissolved and then placed the egg inside. Placing the ruler inside the beaker we measured the height from the boPom of the beaker to the top part of the egg. Again, two addiGonal measurements were taken. Methods • The egg was then taken out of the water and placed in a plasGc container. Using again the 50ml beaker we measured an addiGonal 15ml of salt and then added it to the water. AJer it dissolved we placed the egg once again in the water and took the three measurements. • The egg was again taken out of the beaker and placed in a plasGc container. We then measured another 15ml of salt and added it to the water. We placed the egg in the water and obtained the measurements. • The egg was once again taken out and the last 15ml of salt was added to the water. Once the salt was dissolved and the egg was placed in the water we obtained the final three measurements from the boPom of the beaker to the top part of the egg. AJer this process was done we took the egg out of the beaker and place it again in the plasGc container. Results Egg and Salinity Trials Results Height of zzTop of Egg (cm)
Salinity and the Buoyancy of an Egg in Water
120 110 100 90 80 70 60 50 56.33 40 30 20 10 0 0 106.00 107.67 76.67 58.00 Trial Average
15 30 Salt (mL)
45 60 Results • Depicted in the ‘Egg and Salinity Trials” table, as the salinity of the water increased with each 15mL increment of salt added to the soluGon, so did the buoyancy of the egg. The egg was at its lowest point, at the boPom of the beaker, with an average height of the top of the egg at 56.33 cm. • The addiGon of 15 mL of salt increased the height of the egg just slightly to 58cm from the boPom, and added 1.67cm to its height. The addiGon of another 15 mL of salt, totaling 30 mL in the soluGon, brought the egg’s average height to 76.67 cm, an 18.67 cm increase over the last. • ConGnuing, with the addiGon of two 15 mL increases in salt, the egg’s height increased to 106.00 and 107.67 cm, relaGve to the increase of salt and the salinity level of the soluGon, revealing that the soluGon’s salinity increased its density over that of the egg’s, causing it to float. Results • “Salinity and the Buoyancy of an Egg in Water” is a graphic depicGon of the increase of the egg’s height relaGve to the addiGon of salt and the salinity level of the soluGon, with its greatest increase shown between the addiGon of 30 and 45 mL of salt; reaching its plateau between 45 and 60 ml. Conclusion The purpose of this experiment is to assist students in making a connecGon between global warming and the effects of great ice masses, such as Greenland, melGng and causing a reducGon in the salinity of the Earth’s oceans. From this experiment, students will learn that by adding salt to the water, they will be able to make an egg float. We found that the more salt that was added, the denser the water became, thereby allow the egg to float in the water. Our hypothesis, for this experiment, was that it would take 45mL of salt, added to the water, for the egg to float. Our tests found that with no salt in the water the egg measured on average 56cm essenGally, the egg was resGng on the boPom of the beaker. With the addiGon of 15mL of salt, the egg rose to an average of 58cm, it showed very liPle change. AJer adding a total of 30mL of salt to the water, we found the egg had risen dramaGcally; the egg was, on average, 76.7cm from the boPom of the beaker. We again saw an impressive rise aJer adding another 15mL of salt to the water, for a total of 45mL of salt, the egg now measured an average of 106cm, as measured with the ruler. Finally, aJer adding more salt for a total of 60mL into the warm water, our egg reached 107.7cm on average; clearly our water had become denser. Our experiment showed that it took only 30mL of salt being added to the fresh water before we saw a dramaGc rise in water density as demonstrated by the floaGng egg. This experiment can be used to illustrate one effect of global warming on the planet Earth. Our experiment proved that the salt content of water greatly influences water density. When we started the experiment, the egg was placed in fresh water and did not float but merely rested on the boPom of the beaker. AJer adding 30mL of salt, the water became denser and the egg was able to float. Water density, due to salt content, was the only variable and therefore the cause of increased density. Water density has a direct effect on the paPern of water circulaGon throughout the Earth’s oceans. ScienGsts are studying the effects of freshwater ice melGng in areas of Greenland adding more fresh water to the oceans. Because saltwater is denser and heavier than freshwater, this "freshening" of the North AtlanGc makes the surface layers more buoyant. That is a problem because the surface water needs to sink to drive a primary ocean circulaGon paPern known as the Great Ocean Conveyor. Great Ocean Conveyor Belt In this conveyor belt, sunken water flows south along the ocean floor toward the equator, while warm surface waters from tropical laGtudes flow north to replace the water that sank, thus keeping the Conveyor slowly moving along. An increase in freshwater could prevent this sinking of North AtlanGc surface waters, slowing or stopping this circulaGon. This water circulaGon helps to distribute the Sun’s heat around the Earth and affects temperature and weather paPerns. For this reason, the salinity and buoyancy of the ocean waters are extremely important to inhabitants of the Earth. The egg experiment helps to illustrate the effects of salinity on water density. In this way, students can more easily comprehend the Ocean Conveyor, how ocean density affects the currents, and the impact that “freshening” of the Earth’s oceans could have on the Earth. The difficulGes with our experiment mostly stemmed from the aPempt to get precise measurements of the egg. Our experiment could have been improved with the use of a ruler with a caliper to enable us to more easily ascertain the height of the egg. It was oJen difficult to determine the exact measurement, due to the curvature of the egg shell and a caliper would have allowed for more precision. AddiGonally the use of kosher salt would have leJ the water clearer and thereby easier to read the measurement of the ruler. Also, conducGng our experiment on a fixed cabinet would have eliminated the shaking that oJen occurred with the table, making it more difficult to measure the egg. The End