Osmosis Of An Egg

Published Date: 02 Nov 2017

Introduction

The cells in our body are surrounded by selectively permeable membranes that allow water molecules to pass in and out of them freely. Water is important to the functions of cells because it provides an environment for cellular processes. The process by which water passes in and out of cells is called, osmosis. Osmosis is the diffusion of water across a semi-permeable membrane (Marieb & Hoehn 2010).

During osmosis water moves down its concentration gradient from areas of high water concentration and low solute concentration, to areas of low water concentration and high solute concentration. For example, if the concentration of water outside the cell is lower than the concentration inside, the cell is said to be in a hypotonic state. A hypotonic state causes water to be diffused into cells until equilibrium is reached (Marieb & Hoehn 2010).

However, if the concentration of water outside the cell is higher than the concentration inside, the cell is said to be in a hypertonic state. A hypertonic state causes water to be diffused out of the cell until equilibrium is reached. Furthermore, if the concentration of water is equal inside and out, the cell is said to be in an isotonic state where water diffuses in and out of the cell at equal rates (Tilley & Ross 2011). The purpose of this experiment is to observe the process of osmosis using an egg as a model.

Image 1.0

Materials

The materials used in this experiment are common household products (refer to image 1.0) that included one large uncooked chicken egg, three glass jars, standard household measuring cup, 250 mL of white vinegar, 250 mL of corn syrup, 250 mL of pure water, digital scales, gloves, three sheet of thin paper, tongs, camera, osmosis lab sheet, TI-84 graphing calculator, and Microsoft Excel Software.

Image 1.1

Methods

Day One: To set-up the experiment weigh an uncooked egg on a digital scale in grams. Measure out 250 mL of vinegar and pour it into one of the glass jars. Label the jar as vinegar. Place the uncooked egg into solution and cover with a thin sheet of paper. Let stand undisturbed for twenty four hours. Immediately, record the weight of the egg (refer to Image 1.1) and all observations on the osmosis lab sheet. In approximately twelve hours make a second observation of the egg, and record any changes visual in the egg.

Day Two: After twenty four hours, carefully remove the egg from the vinegar and rinse it. Observe any physical changes in the egg’s appearance and texture. You should notice that the shell has dissolved. Weigh the egg and pour 250 mL of corn syrup into a second jar, labeled as corn syrup. Place the egg in the jar with the corn syrup and cover. Let stand undisturbed for twelve hours. Immediately, record all observations on the osmosis lab sheet.

Day Three: After twelve hours of soaking in corn syrup, carefully remove the egg. Observe any physical changes in the egg’s appearance. Label a third glass jar as water and measure 250 mL of water. Pour the water into the jar, place the egg into the water, and cover top with a thin sheet of paper. Let stand undisturbed for twelve hours. Immediately, record the mass of egg and all observations on the osmosis lab sheet.

Day Four: After twelve hours of soaking in water, carefully remove the egg from the solution and weigh it. Observe any changes in the physical appearance of the egg. Immediately record the mass of egg and all observations on the osmosis lab sheet.

Observations

Image 2.0 When the egg was placed in the vinegar it weighed 61.4 grams (refer to Image 1.1) and traveled to the bottom of the jar and settled. Approximately fifteen minutes later, I noticed tiny white bubbles forming on the shell of the egg (refer to Image 2.0). After fourteen hours, the egg was covered with the tiny white bubbles and had floated from the bottom of the jar to the middle, along one side. C:\Users\Cat\Desktop\Picture0121131636_1.jpg

Image 2.1 After two days in the vinegar solution, the egg had floated to the top of the glass jar (refer to Image 2.1). The egg was covered with even more tiny white bubbles and it appeared that some had oozed out of the egg. Also, it appeared that tiny pieces of the eggshell were floating in the solution. I removed the egg and rinsed it with cold water. C:\Users\Cat\Desktop\pic2.jpg

Image 1.2

I noticed that the egg had gone through several physical changes. The shell was completely removed leaving a translucent yellow rubbery outer layer, it was a lot larger, and it had a strong order, like pickled eggs. Initially the egg weighed 61.4 grams and now it weighed 90.3 grams. This is an increase in mass of 146.94% (refer to Image 1.2 & Table 1).

Image 1.3 When the egg was placed in the corn syrup it sunk to the bottom of the jar and settled there. Twelve hours later, removed the egg from the corn syrup and observed that it usually flat looking in the middle, as if it has swiveled up. Weighing the egg confirmed that the egg’s mass had decreased 53.28% (see table & chart) in the corn syrup. The egg now weighed 48.1 grams.

Immediately after placing the egg in the jar of plain water, it began to swell back up. I removed the egg twelve hours later and it weighed 94.01 grams (refer to Image 1.3 & 2.2)) which is a 195.61% (table & chart) increase in mass. The egg’s rubbery outer layer was still firm and intact. I investigated it with a magnifying glass for tiny holes and found none. I decided to test the rubbery egg out and bounced it several times on the floor. The amazing egg bounced consistently on the floor without bursting.

Results / Data

Table #1: Changes in Egg’s Weight

Mass Before

Mass After

% Change

Egg with Shell

61.4g

61.4g

0

Egg in Vinegar

61.4g

90.3g

146.94%

Egg in Corn Syrup

90.3g

48.13g

53.28%

Egg in Water

48.13g

94.01 g

195.61%

Discussion

The acetic acid in the vinegar dissolved the calcium carbonate in the egg’s outer shell, converting it to CO2. Vinegar is an acid, while calcium carbonate is a base, and acids and bases react with each other (Marieh & Hoeh 2010). The 5% acetic acid (HC2H 3O2) in the vinegar dissolved (ionized) the calcium carbonate (CaCO3) in the egg shell by the reaction HC2H3O2 + CaCO3 --> CO2 + CaO + 2 H2O (http://science-class.net/ Biology/Osmosis).

When I placed the egg into the vinegar, it sunk to the bottom of the jar because it was denser than the solution (Tomazic & Vidic 2012). As the shell of the egg dissolved and became rubbery, the egg became less dense and floated to the top of the solution (Tomazic & Vidic 2012).

The bubbles I saw on the outside of the shell were carbon dioxide (CO2) bubbles. This reaction allowed fluids to pass through the egg’s membrane. Water molecules diffused from the vinegar into the egg because the concentration of the 5% acetic acid (vinegar) was hypotonic to the inside of the egg which caused water molecules from the vinegar to be diffused into the egg, causing an increase in the egg’s mass (Tilley & Ross 2011).

In the corn syrup solution, the glucose was hypertonic to the inside of the egg, which caused water to travel out of the egg and into the glucose solution, as it attempted to equalize the solute concentration.  The cellular environment became unstable and supersaturated causing the egg to swivel up. Immediately after I placed the egg in the pure water the mass of the egg increased greatly as water traveled back into the inside of the egg. This meant that the inside of the egg was hypertonic to the pure water (Tilley & Ross 2011).

Extensions

The following could be used to extend and connect osmosis to real world problems (O’Brien 2011).

Why should shipwrecked sailors not drink salt water?

How does using road salt used for deicing pose problems for plants and animals?

How does treatment for the medical condition Edema involve osmosis?