NAME: Donna Ha
TITLE: Measuring the Rate of Osmosis Using “De-shelled” Chicken Eggs
INTRODUCTION: In order to fully understand the concept of this experiment, one must first be introduced to diffusion. Diffusion is a spontaneous process by which molecule particles move from one area that is highly concentrated to another area in which its concentration is lower. Cells contain fluids and are surrounded by fluids; in order for a cell to function it is required to be in a balanced state. The progress in which a cell is in its balanced state is called equilibrium. Diffusion is a functioning way for cells to reach their equilibrium. Equilibrium is reached by controlling what enters and exits the cell through a cell membrane that selectively filters molecules by slowing down their movement, allowing them to pass through, or not allowing them to pass through the membrane. Diffusion and osmosis go hand-in-hand. Osmosis is generally the same as diffusion, however, deals solely with water. Osmotic pressure is the pressure of a solution against a semi-permeable membrane to prevent water from flowing into the membrane. In this lab, we are going to study tonicity; tonicity is the measure of this osmotic pressure and is the differential of pressure between two solutions separated by a selective membrane. To help identify the relative concentrations of solute particles of different solutions, we must understand that there are three possible differences in concentrations between a cell and its environment. The terms hypotonic, hypertonic, and isotonic are used in referring to the identification of the possible relative concentrations. The first term, hypotonic, is the solution that contains lower concentrations of solute particles, which means that the concentration inside the cell is greater than the concentration outside. A hypotonic solution causes the cell to swell in size. The second term, hypertonic, is the solution that contains higher concentration of solute particles, which means that the concentration of the cell is less than that outside the cell. A hypertonic solution causes the cell to shrink in size. Lastly, the third term, isotonic, is the solution in which the cell stays the same, which means concentrations inside and outside the cell are equal, so water enters and exits the cell equally resulting in equilibrium. OBJECTIVE: The objective of this lab is to identify each egg in its relative concentration of solute particles of different solutions as either a hypotonic, a hypertonic, or an isotonic solution based on the change in each egg’s mass from time 0 to time 60 in minutes. With that, one’s aim is to find the concentration of the unknown solution given by the instructor, and to identify at which point an isotonic solution occurs. HYPOTHESIS: If an egg is placed in a hypotonic solution, then the egg will increase in water mass and swell. If an egg is placed in a hypertonic solution, then the egg will decrease in water mass and shrink. MATERIALS AND PROCEDURE:
In order to proceed in the experiment, the following materials were obtained: •
6 de-shelled eggs
Beakers of solutions containing 0%, 10%, 20%, 30%, & 40% sucrose and an unknown solution To begin this experiment, first each group was given six de-shelled eggs, a scale, weighing trays, paper towels, a timer, and beakers of solutions containing 0%, 10%, 20%, 30%, 40% sucrose, and an unknown solution. To get this lab started, the scale was first plugged in. Once the scale was plugged and ready for use, we placed the weighing trays on the scale and tarred it to zero, so that the tray’s weight wouldn’t have any impact on the weights of the eggs. After the weighing trays were tarred, each egg was placed atop the trays and the initial weight of the eggs were measured and recorded in lab notebooks under results in Table 1 Chart. Correspondingly, each of the six de-shelled eggs were placed in the various...
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