Lab Report: Experiment on conducting Osmosis and Diffusion
Introduction
Generally, osmosis is the biological process through which molecules of water or solution moves from a highly concentrated region to a lowly concentrated region via a semi-permeable membrane. For this reason, osmosis is considered a special type of diffusion since it only entails the movement of water particles. Campbell asserts that osmosis strictly constitutes water molecules’ movement from their highly concentrated region to a lowly concentrated area.
Generally, the rate at which osmosis takes place is affected by several factors. These factors include; the temperature at which the osmosis is taking place, the size of the particle, concentration gradient, and the membrane size. The rate of osmosis increases with an increase in temperature (Hawthorne, 1930). For instance, at a high temperature, the particles attain high kinetic energy and can move faster; hence, the rate of osmosis is high. On the contrary, at a low temperature, the particles lack the necessary kinetic energy to accelerate their movement past the selectively semi-permeable membrane.
Additionally, the particle size has a great impact on both diffusion and osmosis rates. As earlier asserted, osmosis is a special type of diffusion, and for this reason, osmosis cannot occur without diffusion. Particle size affects the diffusion rate in that when the size of the particles is small, the rate of diffusion will be high. On the contrary, when the particles are large-sized, the diffusion rate will be slowed down because the perforations found in the semi-permeable membrane do not allow large-sized substances to pass through with much ease compared to small-sized one. In the experiment on osmosis, it is found that the water molecules move from highly concentrated region to lowly concentrated area via the membrane dialysis bag by the process of osmosis much quickly because of they are small-sized.
The small size of the particle allows the free movement of the particles through a semi-permeable membrane. Additionally, the concentration gradient also changes the rate of both osmosis and diffusion. For instance, the concentration gradient increases with an increase in diffusion and osmosis. Consequently, when the concentration gradient of the solution is low, the rate at which the diffusion and osmosis of the particle will below. Basically, in osmosis, the water molecules movement is always from hypotonic to hypertonic solution. A hypertonic solution contains more solute molecules than water molecules, and therefore it is a highly concentrated solution.
Additionally, a hypotonic solution is referred to as a solution containing more water molecules than solute molecules, which is termed to be a lowly concentrated solution. When the difference in the degree of concentration between the membrane’s inner and outer region is high, the rate at which water molecules move will be high. On the contrary, when the difference in concentration is so small, the rate at which osmosis of the water molecules will below. The role of the concentration gradient plays a significant role in experiments on diffusion and osmosis.
A membrane that is semi-permeable is that which has a layer that permits only passage of a specific size. Dialysis bags will be used as a semi-permeable membrane in the experimental procedure
Experiment on Osmosis
Materials for the Osmosis Experiment
The following materials were used in the two experiments on osmosis; five dialysis bags, clamps, water, at least 20 ml of 30% concentrated sucrose solution, at least 20ml of 40% sucrose solution, at least 20ml of 35% sucrose solution, and dialysis tubing.
Procedure for Osmosis experiment
In the experiment on osmosis, clamps were placed on both ends of the tube. This was done to maintain solutions in the respective bags and the appropriate position. Two bags were filled with normal water. Each of the remaining dialysis bags was filled with 10ml of 30%, 35%, and 40% of sucrose solutions, respectively.
To experiment, the solutions were carefully prepared in the laboratory. The two bags acted as a semi-permeable membrane in this experiment. The bag contains small perforations and is therefore capable of allowing free movement of water particles through the bag. Since the apertures are too small, only water molecules are allowed to pass, and not sucrose molecules are large, and therefore they can squeeze through the small perforations. Four bags were put in four different beakers containing normal water. The remaining bag was put in a solution of 30% sucrose.
The first bag was filled with the same amount of normal water. The second, third, and fourth dialysis bags were filled with 10ml of 30%, 35%, and 40% sucrose solution. Lastly, the water was filled up-to-the fifth dialysis bag. Before the dialysis bags were clamped, they were ensured that air was removed as much as possible. Furthermore, all the bags were made sure that they are soft and floppy. The essence of these procedures was to ensure that the experiment works efficiently and appropriately so as the right result can be recorded. After that, the first four dialysis bags were put in different beakers with tap water.
On the contrary, the fifth dialysis bag was put in a beaker with 35% sucrose. The five bags remained in their respective beakers for ninety minutes. However, for the whole of the ninety minutes, all the dialysis bags were quickly drawn from their separate solutions every ten minutes, and their weighed measured and recorded.
Results for Experiment on Osmosis
The experiment shows that the rate of osmosis was high when the bag contained a lowly concentrated solution. On the other hand, the more concentrated the content of the dialysis bag, the more mass of the bag reduces. The graph obtained from the data collected indicates a difference in the corrected variation in weight. From observation, it was found that the dialysis Bag containing 30% solution recorded the least weight gain. This is so because of the low concentration of sucrose. Due to low concentration, water diffused to the bag via the semi-permeable membrane of the dialysis bag slowly. As earlier alluded in the introduction, the concentration gradient plays a great role in the osmosis rate. When the concentration difference is low, the diffusion of water molecules also slows down.
On the contrary, when then the magnitude of the concentration is high, the water diffusion rate is increased. The bag with 35% sucrose gained more weight than the one containing a 30% sucrose solution. This is because the concentration was doubled from 30%, and therefore the rate at which the bag gained water also doubled. The water entered the dialysis bag containing 35% sucrose at a higher rate than the 30% sucrose solution. The bag containing 35% sucrose gained the most weight as compared to the others. This result can be attributed to the fact that its concentration was very high, and therefore, osmosis was at a higher rate compared to the others. The bag had the most significant magnitude of the concentration gradient. Therefore water moved much quickly through the membrane of the dialysis bag, thus recording the highest weight gain.
Discussion for the Results for Osmosis Experiment
The result indicated the bag containing 30% sucrose, which gained a weight of 3.2g of water over one hour thirty minutes of the experiment. Additionally, the one with 35% sucrose gained a total weighing 5.7g in due course of the experiment. On the contrary, the bag with a 40% solution recorded a total weight gain of 9.1g throughout the experiment. The bag with water was put in a beaker with 35% sucrose posited a complete weight loss of 4.3g.
Though the experiment was carried out successfully, the results suffered from errors. These errors can be attributed to the fact that the five dialysis bags were not removed from their respective solutions simultaneously. For a more accurate result, there is a need to record the bag’s mass at equal time. By doing so, more precise and precise results can be obtained.
Diffusion Experiment
Materials used
The following materials were used in experimenting. Three Petri dishes, potassium permanganate, warm, cold, and normal water. Stopwatch and a thermometer.
experiment 1
Method
The Petri dish was prepared in the same interval, and water of different temperatures was poured in each petri dish until they get full. A small portion of potassium permanganate was put in each of the water content in a separate petri dish with different temperatures. The stopwatches were started immediately when potassium permanganate was dropped in the water content. The time was given so that to ensure the dark purple color filled the entires Petri dishes. Then, the stopwatches were paused immediately when each dish was filled with purple color. Data was recorded to each of the dishes when they got filled with a dark purple color.
Result of the experiment
Results taken to determine the time taken for diffusion to complete in three different water temperatures during the experiment were as follows. Time taken for potassium permanganate to diffuse in the cold water was 50minutes, in the normal water was 30minutes, and in hot water was 10minutes.
Analysis and discussion
During the analysis of the experiment conducted, it was found that potassium permanganate took less time to diffuse in hot water. Thereby, this showed that the increase in temperature accelerates the rate of diffusion. Furthermore, it was explained that the potassium particles’ movement was vigorous in hot water, which made it diffused with a short time. The diffusion rate analyzed using cold water showed that it took the longest time than the two. The cold water of fewer than ten degrees Celcius slowed down the pace of diffusion. Therefore, it was found that potassium permanganate particles in cold water were moving less vigorous, reducing the diffusion rate. The diffusion was at a moderate pace in the normal water. This was explained by the fact that there is no movement of water particles that can accelerate the movement of the potassium permanganate particles. The difference in water temperature determines this such a significant variation in potassium permanganate diffusion in water. In this case, the water temperature used in the experiment was seventy degrees Celsius, forty degrees celsius, and twenty degrees celsius. From these data, the conclusion made was that the rate of diffusion dramatically increases with an increase in temperature, and the rate decreases with consequent degrees in water temperature.
Experiment 2
Procedure
Following a similar procedure, the second trial experiment was conducted using the same water temperature but the different potassium permanganate crystal particle sizes. The dimensions used were 20cm, 10cm, and 5cm. Each was placed in the water simultaneously, and the stopwatches were started at the same time.
Results
Data recorded during the end of the experiment was as follows. 20cm potassium permanganate particle took 50minutes to diffuse, 10cm particle took 20minutes to spread, and 5cm particle took only 2minutes to diffuse.
Analysis and discussion
During the analysis, it was found that the size of the particle determined the diffusion rate. As a result, it was found that the tinny the particle, the rate of diffusion is directly proportional to the size of the diffusing particle. The explanation given was that the tiny particle has a large surface area exposed to the environment, and the larger the particle, the smaller the surface is exposed.
References
Campell, Reece, Urry, Cain, Wasserman, Minorsky, & Jackson (2008). AP Edition Biology (8th
ed.). San Francisco, CA: Pearson Benjamin Cummings.
Hawthorne. Diffusion, Osmosis, and Osmotic Pressure. The Scientific Monthly. (1930) 31.6535-
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