Diffusion & Osmosis (Joy Burton)
Research Question and Hypothesis
What are the various effects of liquids on an egg cell? My prediction, as to the outcome, is that the eggs in any liquid will change in mass and volume due to the diffusion of various liquids through the cell membrane. The egg, not in any water, will neither increase or decrease in mass and volume; the egg in the distilled water will increase in mass and volume ; the egg in vinegar will increase significantly in mass and volume; the egg in Karo syrup will shrink in mass and volume. The movement of substances across the cell membrane is due to the principles called diffusion and osmosis.
Standards
Grades 7 through 8
7.7 Scientific progress is made by asking meaningful questions and conducting careful investigations. Students should develop their own questions and perform investigations. Students will:
7a Select and use appropriate tools and technology (including calculators, computers, balances.....to perform tests, collect data, and display data.
7b Use a variety of print and electronic resources (including the World Wide Web) to collect information and evidence as part of a research project.
7c Communicate the logical connection among hypotheses, science concepts, tests conducted, data collected, and conclusions drawn from the scientific evidence.
7d Construct scale models, maps, and appropriately labeled diagrams to communicate scientific knowledge.
7e Communicate the steps and results from an investigation in written and oral presentations.
8.3 Structure of Matter
3d States of matter (solid, liquid, gas) depend on molecular motion.
3e In solids the atoms are closely locked in position and can only vibrate; in liquidsthe atoms and molecules are more loosely connected and can collide with and move past one another, and in gases the atoms and molecules are free to move independently, colliding frequently.
Grades 9 through 12
Standard Set 4. Gases and Their Property: The kinetic molecular theory describes the motion of atoms and molecules and explains the properties of gases. Students know:
4a. Random motion of molecules and their collisions with a surface create the observable pressure pm that surface.
4b. The random motion of molecules explains the diffusion of gases.
Standard Set 6. Solutions are homogeneous mixtures of two or more substances. Students know:
6a. The definitions of solute and solvent are known.
6b. How to describe the dissolving process at the molecular level by using the concept of random molecular motion.
6c. Temperature, pressure, and surface area affect the dissolving process.
6d. How to calculate the concentration of a solute in terms of grams per liter, molarity, parts per million, and percent composition.
6e. The relationship between the molarity of a solute in a solution and the solution's depressed freezing point or elevated boiling point.
Standard Set 1. Cell Biology: Fundamental life processes of plants and animals depend on a variety of chemical reactions that occur in specialized areas of the organism's cells. Students know:
1a. Cells are enclosed within semipermeable membrane that regulate their interactions with their surrounding.
Experimental Design
Students will measure the mass, volume of eggs and changes, if any that occur, over time. The experiment will have four different setups. Eggs will be placed in various liquids (distilled water, Karo syrup and vinegar) and one with no water. Mass and volume of each egg will be recorded, results graphed, then each will be compared to each setup.
Independent variable
The independent variable is the amount of diffusion/osmosis action that may occur over time. Mass and volume will be measured to determine if processes of diffusion and osmosis occurred.
Dependent variables
The dependent variables are the various liquids (distilled water, vinegar, Karo syrup), the concentration of dissolved solutes and the amount of time eggs are in the various solutions. The mass and volume of liquid will be measured to determine if the various liquids of diffusion and/or osmosis process occurred.
Series
The series that will be tested are osmosis and the diffusion of various substances through an egg cell membrane as a function of mass and volume in various liquids over time.
Constants and Controls
The factors that are held constant are the soaking process, amount of time each is soaked, method of measurements, time of day eggs are measured and the amount of liquid in each setup. The factor that serves as the control is the egg in no water.
Materials
4 (1000) mL beakers or large clear jars, or graduated cylinders
Water (distilled water)
Karo syrup
Vinegar
Eggs, one for each setup
Balance
Petri dish (Used to place eggs in for measurements.)
Paper towels (Used for drying/blotting eggs.)
Marking pen
Data table (Document used to record observations)
Goggles
Apron
Tongs
Cover for each setup
Procedures
1. Identify and label each setup's beaker.
2. Place three eggs in vinegar.
3. Replace vinegar as necessary until the shell has completely dissolved.
4. Once shells have been dissolved,carefully remove the eggs from the vinegar.
5. Blot dry eggs, then weigh each egg.
6. Place one egg in fresh water.
7. Place one egg in a solution of saturated sugar.
8. Place one egg in vinegar.
9. Predict what will happen to the mass and volume of each egg.
10. Check predictions
11. Make measurements at the end of the period and again on the next day.
12. Clean up lab area
Observations & Graphs
In the control, series 1, there were no visible or measurable changes that occurred. The series that seemed to have experienced the most significant changes was series 4, the egg in the Karo syrup. The egg shrunk
due to the movement of its liquid, mainly water, into an area of less concentration, the syrup. At the time of the last reading, this egg appeared transparent, except for its yolk and the yolk appeared as an intense yellow color. The egg in the vinegar, series 3, its size continued to increase, indicating that there was some evidence of diffusion that occurred. It possibly could be assumed that the vinegar moved from an area of high concentration, outside the cell, into the cell where there was no vinegar concentration, causing the egg to swell. However, on the last measurement the mass of series 3, started to decrease, which may mean that substances are becoming equally distributed across the membrane. The egg in the water, series 2, showed no change till the second reading, at which time the mass spiked, but eventually slowed and began to leveled off as well.
In this experiment volume was determined by the amount of water the egg displaced. The concentration of a substance is the amount of the substance in a given volume. When there is a higher concentration of dissolved solutes and the lower the concentration of water the greater the differential in water concentration. The osmotic pressure built up in all cells, except series one and four.
Series 2 had a significant change after reading two, in its volume, till the fifth reading. This may be due to the fact that the diffusion process began to slow at this point. The mass of the egg in series 2 did not show any significant
Analysis & Conclusions
Eggs have an outer shell, and just inside their shells is a cell membrane, which control what goes into and out of the cells. Their membranes are semipermeable, which allow some substances to pass through their pores while others cannot. In order for particles to pass through their pores, their pores must be large enough for particles to pass. In diffusion particles of a substance move through cell membranes from areas of high concentration to areas of low concentration. Diffusion brings nutrients into a cell and rids a cell of wastes. When particles of a substance become equally distributed on both sides of the the membrane diffusion can no longer be observed. Osmosis is the diffusion of water through cell membranes.
According to the kinetic theory of matter all atoms and molecules are in constant motion. As they move, the molecules bump intone another. And, the hotter a substance is, the faster its molecules or atoms move. The more molecules there
change between the fourth and sixth reading. Series 3 did not take a significant turn till the third and fifth reading, at which time the egg's volume increased, but started to decline at this point. Both the mass and volume of series 3 began to drop significantly on the sixth reading.
The correlation is possibly important because the movement of molecules into and exiting out of a cell region depends on its volume. The volume of the egg dropped, perhaps the concentration of substances possibly began to equalize across the membrane. At which time diffusion could no longer be observed.
are in an area, the more collisions there will be. Collisions cause molecules there will be. Collisions cause molecules to push away from one another. Over time, the molecules of a substance will continue to spread out evenly through the area.
The membrane of a chicken egg is semi-permeable, allowing free movement of water, but restricting ions and larger molecules. Although the chicken egg membrane is hidden beneath the shell, if the egg is soaked for a significant length of time in vinegar, the acid dissolves
the calcium carbonate in the egg shell, exposing the membrane.
Once the membrane is exposed movement of substances can begin to occur. When an egg is placed in vinegar, a formation and collection of bubbles, carbon dioxide, occurs on the surface of the egg shell, which results from the disassociation of the carbonic acid.
An egg in fresh water is hypertonic to the water. Water moves from outside the egg where it is highest to the inside of the egg where it is lowest. This even causes egg tissue to swell or become hypertonic, whereas the egg in the sugar solution shrinks because it is hypotonic.
Osmotic pressure is dependent upon the concentration of dissolved substances. The higher the concentration of dissolved solutes, the lower the concentration of water and the greater the differential in water concentration.The equation for calculating osmotic press is rr=cRT (where rr represents osmotic pressure, R is the universal gas constant, c is the concentration of solute [molarity of solute particles], and T is the temperature in Kelvin.) The osmotic pressure of a 0.020 M sugar solution is 0.49 atmospheres, which equates to approximately 16 feet of water, a significant force (Herr, 1999).
The ability to smell provides important information in the environment and helps to identify useful and harmful substances. As airborne molecules of odors settle on nasal receptors, they send signals to the brain. And, as substances begin to spread to areas of less concentration the odor, as I inform my students, will first be detected by those nearest to the odor, followed by those farthest away. All cell membranes are selectively permeable, which means that some substances can pass through while others cannot. The term permeable comes from a Latin word that means "to pass throughout" (Herr, 1999).
How has food preservation been assisted by the process of diffusion and osmosis? If a bacterium is placed in a highly saline solution, such as the salt brine used to preserve meat, water will flow from inside the bacterium toward the outside, where the concentration of water is relatively low. If sufficient water leaves the bacterium by osmosis, it dies due to dehydration. Thus, salt preserves food by dehydrating bacteria, fungi or other pathogens that might otherwise multiply and spoil the food (Herr, 1999).
Applications to everyday life:
Reverse osmosis and water purification
Putting salt on a slug to kill it and control its population
Preserving food, such as fruits and meats
Nutrition therapy
Plasma solution for the storage of red blood cells
Kidney dialysis
Road maintenance during winter seasons
Prolonging the shelf life of fruits and vegetables
The eggs in all liquid series changed in mass and volume, except the egg not in any liquid; the egg that was not in any water neither increased or decreased in mass or volume; the egg in the distilled water increased in mass and volume; the egg in vinegar increased significantly in mass and volume; the egg in Karo syrup shrunk in mass and volume. The outcome of the experiment supported my predictions. The eggs in liquid did change in their mass and volume. The egg not in any liquid neither increased or decreased in mass and volume; the egg in distilled water and vinegar did increase in mass and volume; and the egg in Karo syrup shrunk in mass and volume.
As evidenced in the change in mass and volume, it can be assumed that the egg cells are semipermeable and the solute was small enough to pass through the membranes of the egg cells causing their mass and volume to change. Diffusion and osmosis did occur in the perspective series, except the series without liquid.
