The reason each dialysis tube of solution shrunk or increased was due to its concentration of water. Expansion diffusion is used to explain a variety of phenomena in numerous disciplines, from the spread of disease in medicine to the process of human settlement in the study of geography. A hypertonic solution is a solution in which the solute concentration is higher outside of the cell; therefore, water will flow to the external environment, causing the cell to shrink. This rate of diffusion is measured by considering the time taken for changes to physical changes to occur. My hypothesis was that the Table 1: Group Data for Experiment:Estimating Osmolarity by Change in Weight Table 2 : Class Data Using Averges from Table 1 : Estimating Osmolarity by Celery Sucrose Solutions Average Sucrose 0m Sucrose 0. Immerse your 3 cubes in the sodium hydroxide solution, noting the time.
To make cubes from gelatin, add boiling water 25% less than the amount recommended on the package to the gelatin powder, stir, and refrigerate overnight. A: 3:1 B: 5:2 C: 4:1 The cube that will be most effective at maximizing diffusion will be the cube that has a surface to volume ratio of 4:1 because it has a higher surface area to volume ratio so it is more efficient. Wear eye protection and rinse splashes off the skin. Purpose:Determine how surface area and volume relate to one another and how the rate of diffusion varies with the ratio of surface area to volume. If this occurs, the results of the difference of initial and final weight will not be accurate. Only a solute's relative concentration, or water potential, affects the rate of osmosis. In the case of plant cells with cell walls , expansion is restricted, so pressure builds.
Works Cited 1 Conduct labs 1A and 1B in the packet 2 Obtain agar cubes 3 -1x1x1 -2x2x2 -3x3x3 3 Cut them diagonally with a knife and measure each side 4 Place them carefully in a plastic cup. Small, neutrally charged molecules such as oxygen, carbon dioxide, and glucose can pass freely through the membrane, while the diffusion of other materials is restricted. As cells grow larger, the ratio of surface area to volume decreases dramatically, just like in your agar cubes. If you have chosen to use hydrochloric acid to soak the cubes, make up the agar with 0. The way we describe the movement from higher to lower concentration or lower to higher concentration is called hypotonic solution and hypertonic solution. Then, we microwaved the agar and water mixture in durations of 45 seconds each, watching the beaker carefully until it was clear, and a bubbling liquid.
We waited 2 hours for the solution to diffuse within the potatoes before taking the final weight. Some factors affecting diffusion are concentration gradient, temperature, pressure, size of particles and surface area to volume ratio. They have surface to volume ratios of 3:1, 5:2, and 4:1 respectively. During osmosis, water moves from regions of low solute concentration to regions of high solute concentration without the expenditure of energy. Eukaryotic cells, such as those in plants and animals, are much larger, but have additional structures to help them conduct the required amount of transport across membranes.
The potato samples act as a cell model and the molar solutions allow us to observe osmosis in the cell, first hand. This error is present in the graph, as the line moves slightly higher above. The steeper the gradient the faster the rate of diffusion. Subtract this from the original volume of the cube and you obtain the volume of the cube that has been penetrated. When we took the dialysis tubes out of each beaker, we saw that they either became more light or heavy by observing how flimsy or firm it became.
Rate of diffusion increases because the larger the surface area the more the surface area through which diffusion can occur. Hypothesis: I expect to find that when the surface area to volume of a cell reaches a certain level, diffusion alone won't be able to supply the cell materials needed, and as single-celled organisms take in and release substances by means of diffusion across the cell membrane, this process limits cell size. My group and I selected three various sizes of plastic containers to act as molds for the agar. This rate of diffusion is measured by considering the time taken for changes to physical changes to occur. Periodically, gently stir the solution, or turn the cubes over.
You will not be able to tell the rate of diffusion, since the whole cube will be purple. Solutions in the bag that consisted of more water lost weight, while solutions in the beaker which contained more water gained weight. There are a number of methods that would have optimized the results of the experiment to come to a more definite conclusion. Important factors include surface area and volume. I predict that as the rate of diffusion will be too slow to deliver materials to the center of the cell in the larger cells, it could result in cell malfunction. Remove after 30 minutes Determine the final weight of the cells Calculate the percentage change in weight and record your results in your lab book Table 2.
In order to do this, large animals like us Humans need special respiratory organs such as lungs for taking in oxygen and removing carbon dioxide. The potatoes that increased in weight, gained water and expanded. The solution of water and sucrose decreased the concentration of free water because water molecules surround the solute molecules. Can be unicellular yeasts or multicellular and filamentous, fleshy. Then, we filled three large beakers enough to submerge the cubes completely with 99 mL and 1% phenolphthalein solution. When this occurs, the limit will make it so the surface area is no longer sufficient to provide nutrients. Expansion diffusion is distinguished from regular diffusion when something spreads outward from a central point.