# EDN336

Last updated 8 years ago

Discipline:
Science
Subject:
Scientific Method

Eggs-perimenting with Buoyancy

What type of water is best for eggs to float in?

5/6/14

Research and DiscussionBuoyancy, what is it? When an object is completely or partially immersed in a liquid, the upward force exerted on the object is buoyancy (Elert, 2014). It is the differences in pressure that are at work on the different sides of the object pushing it around causing it to ultimately float. How well an object can float depends on the density of the fluid compared to the density of the object in the water (Elert, 2014). Thus, we come to the basis of this experiment: what water conditions are best for floating eggs.Water density varies as water temperature varies. When water is hotter it is less dense and denser when it is colder (Perlman, 2014). In order for an object to float it has to be less dense than the liquid it is in. If the object is denser, it will sink. Bodies of water are seasonally affected by temperature changes as the lake surface is heated or chilled (Perlman, 2014). This relates the research back to the purpose of my question. Water temperatures have a big influence on ecosystems and as they change, so does the way water effects surrounding objects. There are study limitations, of course. Eggs are not the perfect stand in, nor does a cup and a half of water (with optional four table spoons of salt) perfectly represent conditions in bodies of water. The study itself has limitations in of itself, as the temperature selection is not large, but it can be expanded. Future research could explore temperature’s effect on buoyancy even further with more temperatures, or more objects. The options are limitless.

Kaleigh Chambers

HypothesisFor non-salt water: I predict that temperatures between room temperature and boiling water will not cause the egg to float at all. Colder temperature may cause eggs to float a little bit.For salt water: I predict that the eggs will float in temperatures between room temperature and cold water. The eggs may not float in warmer temperatures and definitely not in boiling.

Materials Eggs (raw), Water, Salt, Measuring cups (2), Thermometer, Pot, Stove, Tablespoon, Ruler, Ice, Spoon, Towel, Microwave

Independent variable: Temperature of water, salt/non-salt waterDependent variable: Reaction of egg (how much the egg floats)Constant: EggControl: Eggs used in experiment, water used

results

The purpose of this experiment is to determine the best conditions for buoyancy. Will eggs float best in room temperature water? What about on either end of the temperature spectrum? Different water conditions affect how buoyant an object is. Knowing what conditions affect how an object floats can help to develop better floatation devices, and to know how different materials may react to being placed in water.

Rational The salt increases the density of the water, making it more likely that the eggs with float. This will occur best in cooler temperatures but the warmer water may cause salt to dissolve. In my experience cooking eggs in boiling water has not made them float; however, colder water may become denser and help them to float.

The data represented by the graph and in the raw data test is the results of each test. Water was heated up and cooled down throughout the experiment to determine the effects different temperatures had on eggs. The height of each egg was determined by measuring the lowest portion of the egg. Some of the results were unexpected. There was very little floating occurring in the non-salt water, though the non-salt egg floated for around a minute during the 62°F test before sinking to the bottom. The only other non-salt test that showed any floating was at 50°F, confirming my hypothesis that the colder non-salt water would produce some floating. However, the hot water tests were a surprise, as both 155°F and 212°F caused the eggs to immediately drop to the bottom. I had to redo the test for 212°F non-salt egg as the original test caused the egg to drop so quickly it cracked – contrasting this with the fact that 78.3°F, room temperature water, still allowed the egg to slowly drop without cracking the shell.

The salt water tests produced more results overall. Every egg managed to float without difficulty in the salt water. It was shocking to realize that not only did the eggs float in the hotter temperatures that was where they produced the best results. At 212°F the salt water egg was floating 1 2/3 in from the bottom of the measuring cup. I was wrong in my prediction that room temperature and colder temperatures would produce better results, especially as the second lowest temperature, 62°F produced the lowest floatation from the salt water eggs with just 1 1/3 inches.The data trends show that salt water certainly presents the best flotation results over all. Even the lowest height was still much higher than the non-salt water eggs combined. However, the results also show that warmer temperatures are able to cause the eggs to float more – though not by much.

ProcedureAll the materials were gathered first and prepared. A chalk board was used to keep track of the measuring cup designated for salt water testing, and the other for non-salt water testing. The temperature was also written on the board for photo record purposes. When eggs were not being tested they were placed onto a towel to prevent them from rolling off. The initial test was done with room temperature water. Two measuring cups were filled with 1 ½ cups of water. The temperature at the start of the test was 78°F so the cups were left alone until they were room temperature. Once this was achieved, four tablespoons of salt were mixed into one of the cups. The temperatures were taken again and then an egg was placed in each of the cups. The eggs were allowed to settle for about a minute before the measure of flotation height was taken. This measure was taken from the lowest portion of the egg.Next, ice was used to lower the temperature in the non-salt water cup. The salt water cup was placed into a freezer. This was done to prevent having ice dilute the water and to also speed up the process. The non-salt water cup had to be emptied a little so that it remained at the same height to prevent messing up height results. Once the water reached the desired temperature of 62°F the tests were repeated.This process was repeated once more for the 50°F test.For the hotter tests, water was warmed in a pot on the stove. The measuring cups were emptied and then washed with warm water to prevent cracking. Then the hot water was poured to each cup, and one cup was mixed with four table spoons of salt. The eggs were lowered into the cups using a spoon for safety. The cups for the next test were warmed in a microwave. I picked 212°F for this test as that allowed the salt water to boil. More water had to be added.The 212°F test for the non-salt egg had to be repeated at this point because I had dropped it too quickly into the water and it cracked.

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