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- We want to examine whether ad how the rate of diffusion over time is dependent on the cubes surface area to volume ratio SA:V. Smaller cubes have bigger SA:V than big cubes. We know that e. We will therefore see, whether one of the reasons they do...
- We measure the NaOH with a weight and the volume of water with a measuring cylinder. We put the beakers in the bath. It was bought at a chemical store and the package was labelled. The method of measuring the length of We use the same ruler for all...
Lab Report = Surface Area To Volume Ratio Effect On Diffusion
The visible trend is called decelerating increase. The relationship between the variables has its explanation. The obtained results have a reflection in the biological world. Cells need to take in nutrients from their surroundings and expel waste through their cell membrane. If there is a large surface area to volume ratio, there is more cellular membrane to take care of both of these functions.- The first thing, which contributed to the low reliability of these experiment is a small, insufficient number of trials. Second of all, it was already mentioned that the data collected by group number 6 is very different from the data collected by the other groups. It is very probable that this group has misunderstood the method. Both the odd results of group 6 and the high value of standard deviation can be the result of other human errors. Keeping the cubes in the solution much more or much less than 10 minutes has probably affected the results most significantly — the diffusion would be at a different stage. The same happens with waiting too much between removing the cubes from the solution and taking measurements. Thirdly, what can have some effect on the low reliability is that different people were taking measurements using rulers with different errors.
- Uncertainties themselves might have affected the results only on a very small scale as they all had a small range. Considering the weaknesses of this experiment we should avoid repeating the same mistakes next time. First of all, it is better when much more trials are conducted preferably tens , but the same person, using only one ruler with a specific error, does them all. What should also be improved is the accuracy in the adherence to the time the cubes should stay in the solution. The measurements are to be taken immediately after removing the cubes — it will prevent any undesired processes to start and change the results.
- A good idea to extent the experiment is to examine more cubes with more different sizes. This will give us an image on how does the correlation between SA:V and diffusion rate look in a full spectrum, does it stay in the same trend as this experiment has shown or not.
How To Teach Osmosis And Diffusion With Agar Cubes – A Free Activity
Limits to Cell Size I love this lab! It really let's students explore the relationship between surface area, volume, and diffusion time. And quickly allows them to see that a large cell will starve or poison itself since material can't diffuse in or out fast enough. I make bromothymol blue agar see recipe below , but you just need something safe that will change color as it changes pH. Students cut various sizes of cells and place them in vinegar to watch -- and time -- the movement of color change as the vinegar diffuses in turning the blue to yellow. The variety of cell designs from my class The winning design for Isn't it amazing how much it models intestinal villi and we didn't even learn about that yet!- The cubes during the diffusion process Cell design from my class Cell designs from my class Cell design from my class Recipe to make Bromothymol Blue Agar for Cell Races Mix 15g agar in 1 liter water. This is AGAR, not agarose. Note: 15g is thicker than you would make for growing bacteria, because you want the agar stiffer and tougher for handling. It is better to use plain agar and not LB agar, so it has less of a chance to grow bacteria.
- Boil slowly in microwave or hot water bath until agar is melted granules will disappear. Watch for and avoid boil-over. Remove from heat. Add 0. If the mixture is not dark blue, then add more bromothymol blue. If the mixture is green or yellow, you will need to stir in drops of NaOH or another base until it turns blue. Wear safety goggles and gloves when handling NaOH. Pour the agar into trays. For the initial lab, I make the agar in rectangular trays, like a wide silverware tray or a square Pyrex dish -- enough to be at least 2cm deep -- and slice chunks for the students to cut from.
- I use the tops of my microcentrifuge storage boxes most of the time: See this image , but just tape that little curved indent with masking tape For the actual contest, I mold them in ice cube trays that I bought at Amazon and use a spatula or butter knife to remove the gelatinous cubes. Make enough for ice cubes per student or student group. Let agar harden at room temperature or in refrigerator. Can be made a couple of days in advance. Cover with plastic wrap to keep from drying out and store in refrigerator, otherwise it will get a lot of bacterial growth quickly, especially if you use nutrient agar. From the microcentrifuge trays students cut blocks of specific sizes: 1cm x 1cm x 1cm 2cm x 2cm x 2cm 1cm x 1cm x 8cm Students have to calculate volume, surface area, and SA:V ratio.
- Students then immerse each block in common household white vinegar either in small beakers or in more tray tops. Agar turns yellow in acid. You can easily see the blue core disappear as diffusion takes place. Students time until blue completely disappears. Helps to put beakers on white paper as a background. You'll notice that 2x2x2 and 1x1x8 have same volume, but different surface area You'll be amazed at how long 2x2x2 takes minutes! I usually have them start the 2x2x2 block first since it takes longest and then run others concurrently. You may need multiple stop watches or good records as to when the later blocks were immersed in their separate beakers. And now for the Competitive Cell Races! This process allows students to confront a lot of misconceptions of cell design. No poking, prodding, touching beaker containing agar cell in vinegar.
- Students mass agar at conclusion of race Disqualification if cell breaks upon massing although you can be a bit lenient here. We sometimes run a second race after a trial run, so students can improve designs. I make a lot of agar just in case. It's a fun learning day!
- Damien Raspanti Method:1 Cut the Agar in three 3 sizes including: 1cm, 2cm and 3cm cubes, using a ruler and knife. This indicates that diffusion in the cube has occurred. If the cube has a larger surface area and volume, less phenolphthalein diffuses. Therefore the smaller the cube, less volume and surface area the faster the rate of diffusion.
- Thus resulting in minimal residual of colour. The most effective sized cube that maximised the rate of diffusion was that of the size 1cm 3. This size was the most effective has it had a smaller surface area to volume ratio. Therefore, following the concentration gradient, this allowed more molecules to enter a smaller surface area. The main factors that affect the diffusion of materials include: lipid solubility, molecular size and electrical charge. Cells can grow as large as they need to. However, for efficient function cells must maintain a high surface area to volume ratio. The body adapts surface area to volume ratios. An important example of this is the exchange of gases such as oxygen. Through the process of breathing, our lungs are able to gain oxygen through the process of respiration, which then encompasses gaseous exchange of oxygen from the blood stream to the capillaries, to the alveoli sacs of lungs by means of diffusion. Cells are usually microscopic in size so that they allow efficient excretion of wastes and only a microscopic cell can have a sufficient surface area to avoid accumulating waste products.
- They also are of a microscopic size as they are able to acquire and utilise the energy required for function at a faster rate. These roles are only able to occur efficiently in microscopic cells. The importance of measurements in this practical help make calculations accurate. In the practical measurements were taken to the nearest centimetre cm , resulting in the calculations that have been presented in Table 1 and 2. If measurements had been taken to the most accurate measurement possible. For example, micrometres. If this had been the measurement taken, results and calculations would have been more specific and more accurate. The practical demonstrated that cells are only able to grow to a certain size.
- This is observed through discerning the impact of surface area to volume ratio. It is known that cells are able to continuously undergo mitosis, however if the cells continually grow there will be no use for their excessive size. Therefore they remain at a limited size. Plants and animals can help to explain how surface area and rate of reaction effects organisms gaining nutrients, gases and eliminating waste. In plants, carbon dioxide CO 2 diffuses from its surrounding air into the leaves, which contains cells. This promotes for photosynthesis. In humans, the surface area of the intestines are small and tight, chewing of food breaks the large into the small. The digestion of food in the mouth involves changes bite-sized pieces of food into smaller molecules.
- Consequently, due to this process it has the effect of increasing the surface area of the food and letting saliva to be mixed with food. Therefore, the surface area that is larger affects the rate of diffusion. Conclusion:The experiment was set out to discover if bigger was better or if smaller was smarter. It also demonstrated how the surface area and volume of an agar cube affected the rate of diffusion. The experiment was set out to find the rates of diffusion for agar cubes. Three beakers had three different sized agar cubes in them and hydrochloric acid was poured onto them. The timer had been started for 10 minutes, stirring the agar cubes at 5 minutes. Once the 10 minutes had been completed, the agar cubes were taken out of the hydrochloric acid and dried. They were then cut in half and the volume of not diffused agar was calculated. The results had revealed that the rate of diffusion depended on the surface area and volume of the agar cube.
- These results are shown in Tables 1 and 2, were the volume of the cube changed after it had been exposed to the hydrochloric acid. The results supported the hypothesis that he larger the agar cube, less diffusion occurred and if the smaller the cube, more diffusion occurred. Figure 3 :3Agar cubes as soon as Hydrochloric Acid was added 6 Keep the cubes inside the Hydrochloric Acid for 10 minutes, turning the cubes at 5 minutes using the spoon. Remove the cubes from the acid and dry them with the paper towel. Figure 8 : 3 Figure 4 :Figure 5 Figure 9 Agar cubes cut in half to work out area of no diffusion 9 Record the depth of penetration, volume left of coloured Agar, percentage left of Agar and percentage of acid penetration in the results table. Reference List: o G. Chidrawi, S.
- When phenolphthalein is exposed to the normal alkaline conditions in the agar, it will look pink. But when it is exposed to neutral or acidic conditions, it changes from pink to clear. You will make different size and shaped agar cubes as a model for cells to study the impact of cell size and shape on diffusion rate. To make the first set of cells, measure out and cut a small cube of agar where each side measures one centimeter. Next, measure and cut out a medium cell cube with sides of 2 cm and a large cell of 3 cm on each side.
- The null hypothesis could be that the acid will diffuse to the center of the small and two larger cubes at around the same time. Add mL of 0. Working in a team, have one experimenter ready with the timer and the second and third experimenters ready to drop each cube into one of the beakers. When the first experimenter says go, simultaneously drop all three cubes into their respective beakers and start the timer. Observe carefully until one of the cubes becomes completely clear or 10 min have passed. Stop the timer, remove the agar cubes from the beakers and place the cubes into a Petri dish.
- Make a note of which of the three cells became clear or had the smallest remaining pink area. Then, also note which cell had the most remaining pink agar. Next, in Table 1, calculate the surface area to volume ratio for each cell. Also consider whether this correlates with your observation of the depth of diffusion into the agar cells. If cells rely on diffusion to deliver essential nutrients and molecules to the whole cell, discuss with your group if it would be better to have a smaller or larger surface area to volume. Now, with the remaining agar, cut three rectangular shaped blocks of different sizes and record their length, width, and height. This will test what happens when the shapes of cells are different. Calculate the surface area of your rectangular cells using the formula below, where length is l, width is w, and height is h. Remove the cell shapes from the solutions and observe the depth that the hydrochloric acid diffused into each of these cells, and which shapes have the smallest and largest remaining pink areas not reached by the solute.
- Using the surface area and volume data you recorded for your rectangular shapes, calculate the surface area to volume ratio of these cells. Additionally, discuss with the group whether these rectangular cells displayed a similar or different pattern of diffusion to that observed with the cube shaped cells, and what this might mean. Then, label the beakers from , and add 0. The null hypothesis is that there will be no difference in the ability to diffuse through the dialysis tubing membrane between the solutes. To prepare the dialysis tubing, remove the pieces one at a time from the distilled water bath and tie a tight knot at one end of each tube.
- These tubes, when filled, will act as model cells with the dialysis tubing acting like the semipermeable membrane. Add 10 mL of starch solution to the first tube and tie off the open end, making sure to leave space in case the tubing expands during the experiment. Then add 10 mL of the NaCl and dextrose solutions to the second and third pieces of tubing, respectively, and tie off both tubes, again, leaving space in case of expansion. After adding 10 mL of distilled water and tying off the fourth tube, weigh each of your model cells. Record the initial weight values in grams and the colors of the starting solution in each tube in the appropriate columns of Table 2. Click Here to download Table 2 After quickly rinsing the outside with tap water, place each piece of tubing in its corresponding beaker for 1 h at room temperature. NOTE: For example, the starch solution tube should be placed into the beaker containing the iodine.
- At the end of the diffusion period, weigh the tubes again. Then, observe the tubes carefully, noting any color changes. Record all of these data in Table 2. Next, to perform a Benedict's Reagent test for simple sugars, make a water bath by adding mL of water to a mL beaker and placing it onto a hot plate. Set the plate to high, to boil the water. Label two new glass test tubes as H2O and dextrose, respectively. Use a graduated cylinder to transfer 1 mL of solution from the water and dextrose beakers into the corresponding test tubes. Then, add 2 mL of Benedict's Reagent to each tube. Once the water is boiling, place each test tube into the water bath for minutes. After this time, note the color of the solution in each tube. Then use this key to assess whether the test is positive or negative and record these data in the appropriate column in Table 2. Click Here to download Figure 1 Results Expand First, look at the mass of your four dialysis tube cells at the beginning versus the end of the experiment.
- Calculate the change in mass for each of the four cells and plot it onto a bar chart. Note which cells demonstrated the most change, and whether any of the cells appeared visibly different in size. For the experiment with the starch and iodine indicator, note whether there was a color change in the fluid in the artificial cell. Also consider whether there was a color change in the water in the beaker, and what both of these observations say about the properties of the dialysis tubing membrane. Discuss with the class which of the molecules you think could and could not pass through the semipermeable membrane.
- Diffusion in agar cubes lab March 14, 1cm agar cube before put in sodium hydroxide. All three agar cubes sliced in half to demonstrate diffusion after removed from sodium hydroxide. The 3cm cube. Conclusion Questions: 1. In terms of maximizing diffusion, what was the most effective size cube that you tested? The 1 cm cube was the most effective at diffusion. With a ratio. Why was that size most effective at maximizing diffusion? What are the important factors that affect how materials diffuse into cells? The 1cm cube was the most effective due to its high surface area to volume ratio It has the least amount of volume to be able to get to the middle and more surface area to diffuse through, compared to its size.
Agar Cell Diffusion: Biology & Chemistry Science Activity | Exploratorium Teacher Institute Project
Important factors that can affect how materials diffuse include volume, surface area, concentration, size and shape of the molecule, and temperature. When cells grow, their volume increases at a greater rate than surface area, meaning the ratio of surface area : volume will decrease, making diffusion less effective. You have three cubes: A, B, and C. They have surface to volume ratios of , , and respectively. Which of these cubes is going to be the most effective at maximizing diffusion, how do you know this? The cube is going to be the most effective at maximizing diffusion because it has the highest ratio, similarly to the 1cm cube in our lab. Comparing those numbers to the data we collected during the lab, I can identify which cube will have the highest diffusion rat due to its surface area : volume ratio. How does your body adapt surface area-to-volume ratios to help exchange gases?
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