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The rate of Hydrochloric acid reacting with magnesium ribbon.
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Introduction In the reaction between hydrochloric acid and magnesium ribbon, the hydrochloric acid will dissolve the magnesium and produce hydrogen gas. All chemical reactions involve reactants which when mixed may cause a chemical reaction which will make products. In my case the reactants are hydrochloric acid and magnesium ribbon. The chemical reaction takes place when the magnesium ribbon is dropped into the hydrochloric acid. The products that are formed during this reaction are hydrogen gas and magnesium chloride. The formula equation for this experiment is: Mg + 2HCl r MgCl2 + H2 Magnesium + Hydrochloric...
be similar to the ones I already have, so I would not use this for any further experiments. The reason I could use a different type of acid for any further work is to find if the is a difference between them if their molecular build up is different.

I could also use the less reactive metals of the reactivity series zinc, aluminium, iron and lead that way I could find the initial rate of reaction at 5 seconds for the higher concentrations of acid like 3.0M or 3.5M and I could find there relative activity.

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Prediction I predict that the... Prediction I predict that the higher the concentration of salt, the lower the mass the potato cylinder will become. This is because there is a greater concentration of water molecules inside the potato cylinder, so the water will drain from the cylinder by osmosis, to where there was a lower concentration of water molecules, so therefore the mass of the cylinder would decrease. If there was a low concentration of salt in the solution, the cylinder would increase in mass. This is because there is a higher concentration of water molecules in the potato cylinder than in the solution. This would mean that the water from the solution will travel into the semi-permeable cell wall of the potato by osmosis to where there is a lower concentration. Key Variables These are the factors that could affect my results: "¢ The temperature of the solution "¢ The concentration of salt solution "¢ The volume of the solution used "¢ The mass of the potato cylinder "¢ The surface area of the potato "¢ The variety of the potato Test Variable The factor that I am going to change to see its effect is the concentration of salt solution. Fair Test I am going to make sure that my experiment is a fair test by keeping other variables which I am not going to change the same. A thing that I am not going to change is the temperature of the solutions. I cannot control weather they will be differed in my experiment, although they will be kept in the same area. I will make sure that I will keep the volume of the solution the same for each of the test tubes by measuring it before I put it into the test tube. I will make sure that I keep the surface area of the potato the same, I can do this by making sure that when I cut the potato cylinder I keep the scalpel vertical so that I do not cut it at a slant. The size of the potato will be the same as I will measure each of the cylinders before I weigh them. The masses of my cylinders may vary and I have taken this into consideration and I will work out the percentage increase/decrease for each cylinder. The variety of potato will be the same as my cylinders will come from the same potato. Apparatus Potato Scalpel Test tubes Measuring cylinder Ruler Scales Salt Distilled water Paper Towels Results Volume of distilled water ml Volume of Salt solution ml Concentration of salt solution M Mass of cylinder before g Mass after g Change in mass 20 0 0 2.60 1.76 +0.34 15 5 0.5 2.18 1.70 -0.58 10 10 1 2.23 2.04 -0.19 5 15 1.5 2.13 2.16 +0.62 0 20 2 2.10 2.76 0.76 Conclusion The concentration of salt had an effect on the mass of the potato cylinder. The effect on the cylinder depends on the concentration of salt. If there is a higher concentration of salt in the solution the cylinder would decrease in mass. The lower the concentration, the higher the positive change in mass. If there is an equal amount of water and salt, then there is not a big change in the mass of the potato. The graph showed me that my line of best fit was almost like straight diagonal line with a positive gradient. I did have one odd result which I could have improved if I had repeated the test. My table showed that the higher the concentration of salt, the lower the mass of the cylinder will be. This is because if there is a high concentration of salt the water in the cylinder will diffuse through the semi-permeable wall of the potato cell where there are less molecules of water.   

Prediction I predict that the higher the concentration of salt, the lower the mass the potato cylinder will become. This is because there is a greater concentration of water molecules inside the potato cylinder, so the water will drain from the cylinder by osmosis, to where there was a...

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Introduction: In this piece of...Introduction: In this piece of coursework I will be attempting to discover what affects the digestion of starch. There are four main factors that affect the digestion of starch. 1. Temperature of the solution 2. PH of the solution 3. Surface area of the starch 4. Concentration of starch As the temperature of the starch gets cooler the rate of digestion will decrease. This is due to the number of collisions occurring during the reaction. If the pH value of the solution is quite high then the active site is affected and can be damaged and the hydrogen bonds are also changed. This reaction or occurrence is known as denaturing. This will result in a poor digestion of starch because the active site forms the gap for the starch particle to go into. The surface area of the starch affects the digestion, the reason for this very simple. If the surface area is greater then the particles are able to react on a larger area so more gets digested. The concentration of the solution will play a great part in the digestion of starch. If the concentration of starch to water is quite low then the reaction will not be as quick because there are not as many particles of the enzyme to react with the starch particles active site. Digestion: Amylase and carbohydrase found in your saliva, works best in slightly alkaline conditions. At a PH of about 7·5. The main types of carbohydrate which you eat are: cellulose, starch, and sucrose. You cannot digest cellulose at all because its molecules cannot be broken down in your digestive system so your body is not able to absorb them. Starch on the other hand is easily digested. The process of digesting starch begins in the mouth. Saliva contains an enzyme called amylase which begins to break down the starch molecules into maltase. You do not usually keep food in your mouth long enough for your amylase to finish digesting any starch in it. However when the food enters the stomach the amylase stops working. This is due to amylase not being unable to work in acidic conditions. Active site: The high degree of specificity shown by enzymes, suggest that the combination of substrate and enzyme is very exact. It is thought that each enzyme molecule has a precise place on the surface, the active site, to which the substrate molecules become attached. In our experiment this is going to be one of the main processes occurring during the practical. The area on the enzyme where the substrate or substrates attach to is called the active site. Enzymes are usually very large proteins and the active site is just a small region of the enzyme molecule. This is what is meant by the "lock and Key Theory" that is the active site. This the active site in its three stages of alteration when it is being heated. The three stages are travelling from left to right. Stage 1= the yellow diagram, Stage 2=the Orange diagram, Stage 3= the whit diagram. This image was gathered from: www.scripps.edu/~ulrich/ three_structures_large.jpg For my experiment I will only be altering one of these factors; temperature. The reason I chose to use temperature as my variable is that I feel that it will give us the most interesting results. However keeping the temperature of the solution the same throughout the time span will not be easy and will probably slightly affect the accuracy of the results. To try and keep my results as accurate as I can and to keep the test fair I will inserting a digital temperature probe into the solution that I am heating and once it has reached the designated degree then I will keep the solution at that constant temperature by withdrawing and advance the Bunsen burner to the heated solution. There will be three other pupils taking part in the experiment with me so I was able to use them to help assist me with making sure that the test was fair. One person was the time keeper so was able to tell me when to take a pipette drop from the solution. Another person had the responsibility of ensuring that the temperature of the solution was at a constant. I will be participating in three experiments, which means I will be doing each temperature three times. This should give me more accurate results and if there are any anomalies then the final results would not be affected because an average would be used to work out the final result and draw the graph. The concentration of the solution will stay the same throughout the experiment so that would be kept fair. Prediction: Amylase is an enzyme found in your saliva and is produced by your salivary glands in the mouth. The purpose of amylase in the body is to break down starch and turn it into maltose molecules, however there is not enough time to completely digest the starch into glucose because the food starch is swallowed before the digestion is finished. By the time the starch has reached the stomach the reaction has stopped. However in our experiment we will have enough time, and so the experiment and digestion of starch will finish. Starch is a polymer, which means that it is a compound that is made up of a number of simple molecules. As soon as the starch ids digested the starch is turned into a monomer single molecule. This substance is known as glucose and is small enough so that it can be absorbed into the blood. Amylase is a 'Biological Catalyst', this means that it will speed up the reaction within the body. Amylase is also 'Temperature Specific' this means that the reaction rate varies in conjunction to the temperature of the solution it is working in. This would mean that there would be a variation in the rate of reaction. As the solution cools the starch and amylase molecules lose energy and so the rate of the digestion of starch decreases. The processes of denaturing is shown below: In this investigation, I predict that as the temperature increases the amount of time taken for the experiment to finish will decrease. So on a graph the results would be placed roughly along a straight line. But I also predict that the reaction will get to a certain stage where the rate of the reaction will reach a stage where it cannot increase any more. This is due to the enzyme denaturing. Another reason for the rate of reaction increasing at first is due to the particles in the solution gain more energy from the heat source Bunsen burner and so more of the bonds are destroyed and broken. This rise in temperature also affects the bonds of the active site and damages them, as a result the active site is damaged to a certain extent that it cannot digest the starch any more. This is known as denaturing. Denaturing is when the active site is damaged to a certain extent due to such a high temperature environment that the rate of the reaction is so long that it will take a long time for the reaction to finish. So, on a graph it would look something like this: This graph was extracted from "BIOLOGY A functional Approach Second Edition M.B.V. Roberts" My reason for this is that usually, as the temperature rises the rate of reaction increases. This is due to the particles gaining greater energy as they are heated and so are causing far more collisions. As a result the amount of time for the reaction to finish will decrease. But I also predict that the reaction will get to a certain stage where the rate of the reaction will reach a stage where it cannot speed up any more. This is due to the enzyme denaturing. Denaturing is when the active site is damaged to a certain extent due to such a high temperature environment that the rate of the reaction is so long that it will take a long time for the reaction to finish. Some of the key scientific reasons are from the following resources: Mary Jones & Geoff Jones and the Robert Nelsons Biology a functional approach. Method: For this investigation I will be testing how the concentration of the solution affects the digestion of starch. The experiment will be carried out by using the following equipment and substances: · Starch solution · Amylase · 1x Boiling tube · 1x water bath · 1x gauze · 1x Heat proof mat · Bunsen burner · 1x pipette · 2x Spotting tile · Iodine solution · 1x measuring cylinder To increase the level of accuracy of the experiment a digital thermometer will be used to provide me with better and more accurate results. I will also perform the experiment 3 times so that if there are any anomalies then they will be clear and not affect the averages. The pipette will be used to extract some of the solution so that it can be tested for starch. The measuring cylinder will be used to measure accurately the volumes of amylase and starch. This is how the experiment will be set up and what it will look like: Preliminary Study We decided to test out our method by doing a preliminary study. For this test we used a range of temperatures from 25-100°C, and with 6 different temperatures in all. This was a good range as on the last temperature it was clear that the enzyme had denatured. However the temperature that the enzyme denatured at was higher than expected. In the real experiment I will be repeating this experiment three times as this will rule out anomalies and make the results more accurate. The method worked well and there were no apparent mistakes or problem with it. Temperature Time taken for starch to disappear Seconds 25 120 40 90 55 70 70 60 85 60 100 +360 The chosen temperatures seemed to work well or this preliminary test so I will be using them for my final investigation. And this also provides me with the information that the enzyme will denature at a temperature between 85 and 100°C and that it will take longer than 360 seconds. Results Here are my results from my the three experiments that I carried out: Temperature ºC wanted Actual temperature ºC Time taken for the experiment to stop Exp 1 Exp 2 Exp 3 Average Exp 1 Exp 2 Exp 3 Average 20 26 25.5 24.5 25.3 120 120 120 120 40 40 39 40.5 39.83 100 100 100 100 55 53 54 56 54.3 80 70 60 70 70 70 70 71.5 70.5 60 50 50 53.3 85 83 85 83.5 83.83 60 60 60 60 100 95 93.5 94.5 94.3 Still not finished after 360 seconds These results were all gathered using the same apparatus and layout like that of the one explained in the method. These results portray quite an accurate set of results. There are no anomalies so the results are very pleasing. It was interesting to discover that the experiment did not finish when the temperature of the solution was at 100ºC. This is most likely be due to the active site being deformed. This is known as denaturing. Denaturing is the word given for change of an enzyme and the our case the amylase is the enzyme for the digestion of starch. The graph's are on the next two pages! Graph 1. "“ This graph displays how the temperature of the solution affects the amount of time it takes for the reaction to finish. As you can see the results follow along a slight descending curve, and then suddenly at around 85-94ºC there is a sudden drastic change in the length of time it takes for the reaction to finish. This would suggest to me that the form of the active site would have been deformed. This would result in the time taken for the reaction to finish would take far longer. Graph 2. "“ This graph is displaying the rate of the reaction in contrast to the average temperatures of the experiment. This graph clearly displays that the fastest time it too for the reaction to finish was 70ºC. From then onwards, the length of time for the reaction to finish dramatically increased. The protein had denatured. In a difference of about 11ºC the rate of reaction had increased by 0.140 on the graph. The reason for this sudden change in reaction rate is due to part of the amylase enzyme active site not being able to brake down the starch molecules efficiently and properly. This is due to the temperature being too high. Conclusion: Like in my prediction there was a certain point in the digestion of starch that the enzymes will not be able to work in the usual way. This is due to the temperature the enzyme Amylase is being worked in is too high and the protein of the enzyme is not able to digest the starch molecule properly. The place where the starch molecule is digested is called the active site. As the temperature of the solution of amylase enzyme and starch molecule increases the active site becomes deformed and is not able to digest the starch molecule properly. Coming back to the lock and key theory, the area on a precise place of the large protein is known as the active site to which the substrate molecule is attached I have discovered that this place becomes deformed when placed in a solution of a high temperature. So, as a result, the rate of reaction as the temperature reaches +70ºC starts to decrease. In our experiment when we had managed to get the temperature of the solution up to nearly boiling point 94.5ºC the time it took for the reaction to finish took so long that we had to stop it early. And as a result the breakdown of the starch is not being catalysed. The protein had denatured and it would have taken a very long time before the reaction had finished. The amylase that we had been using was in fact bacteria amylase instead of salvia amylase. Bacteria amylase has a higher denaturing temperature compared with the salvia amylase. And so the results were slightly different to that of my prediction, however the results did produce a similar graph to that of my prediction. Compare the graphs of my prediction and that of my rate of reaction graph from my results. Evaluation: Throughout this investigation I have tried to be as accurate and fair in everything that I have done whether it be taking readings off the thermometer or measuring out the volumes of the amylase and Starch solutions. The careful detail for accuracy prevailed, as the results did not contain any anomalies, and the graphical results were as predicted. I also feel that they were as accurate as they could have been using the relatively limited equipment available. However, if I had access to more advanced and more accurate equipment then the results would be more accurate and precise. An enclosed environment that was able to change in temperature would be ideal for keeping the temperature of the solution at a constant. Not allowing the solution to fall or rise, unless there was a change in temperature conducted by the scientist. An electric water bath would be a good piece of equipment for this, as it will keep the water at a constant temperature. This constant precise temperature that would be supplied by the water bath would create a graph that would be more similar to that that I used in my prediction. A timed thermometer reader would also give me the actual reading at that particular time so the results would be more accurate on the graph. I think it would be perfect idea if we conducted the same experiment but using saliva amylase and compare the differences with the bacteria amylase that I used in this experiment. Another way in which I could have improved this experiment is to have increased the sampling rate to every 5 seconds. This would have given more accurate results because a lot can happen in every second. However it would not be practical if I took the samples every second because I would not have had enough time to second the date in a time space of 1 second as I would have extract some of the solution and put a drop of it into a spotting ti le with one drop of iodine in it. Ptyalin is an enzyme that occurs in the salvia and is used to help convert the starch molecules into sugar. It would be interesting to discover the role and difference that this has in comparison to when you only use the bacteria amylase. some of the information was gathered from: "A dictionary of Science" by E.B.UBAROV, D.RCHAPMAN, ALAN ISAACS   

Introduction: In this piece of coursework I will be attempting to discover what affects the digestion of starch. There are four main factors that affect the digestion of starch. 1. Temperature of the solution 2. PH of the solution 3. Surface area of the starch...

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