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I am measuring the rate of reaction how fast a reaction takes of sodium thiosulphate and hydrochloric acid. There are different variables I could use to see the change in the rate of reaction. These include temperature, concentration or catalysts. I am going to do two experiments, one changing the temperature and one changing the concentration of the sodium thiosulphate. This is how they will be done. Planning Experimental Procedures Equipment Sodium thiosulphate Na S O of different concentrations Hydrochloric acid HCl Tile marked with a cross Measuring cylinder x2 Beaker x2 Bunsen Tripod Test tube x2 Stopwatch Thermometer As the diagrams show, firstly I will measure the right amount of sodium thiosulphate and hydrochloric acid into two separate test tubes. If it is needed, these will then be put into water and heated with a Bunsen burner and tripod until they are up to temperature, which will be measured with a thermometer in the water. They will then be put into the beaker. Firstly, the experiment will be done with the substances at room temperature. This means that the beaker will be filled with Na S O and HCl via two measuring cylinders and placed on the tile marked with a cross. The amount of Na S O and HCl being put in the beaker will be determined by prior tests, but they will only need to be quite small amounts. As soon as the two substances are mixed together, the stopwatch will start timing and it will stop when the cross is obscured. When the substances need to be heated, they will be put in separate test tubes and heated in a beaker of water as above. They will be mixed together when up to temperature. One of the experiments will show the difference temperature makes and the other will show the difference the concentration of the sodium thiosulphate makes. During the experiments, goggles and aprons will be worn at all times for safety. The tests will be made fair by the fact that only one thing will be changed each time "“ the temperature or concentration of the sodium thiosulphate. We presume that when the concentration of the Na S O is increased, the rate of reaction will be higher. This is because if there are more molecules, they are more likely to collide and react. However, the collision theory says that a very small percentage of these collisions results in a reaction. This is because of an energy barrier. Only those particles with enough energy to overcome the energy barrier will react when they collide. So, if the frequency of collisions is increased, the rate of reaction will increase. However, the percentage of successful collision will remain the same. The particles go through random collisions in which energy is transferred between the colliding particles and this leads to particles with differing energies. The distribution of the energies of a particle of gas is shown by the Maxwell-Boltzmann energy distribution curve, shown below. We would also presume that when the temperature is increased it will have the same effect. This is because the molecules will collide more often and with greater energy and so will be more likely to successfully react because their bonds break. For an average reaction a 10 C temperature rise doubles the rate of reaction because about twice as many particles possess the necessary activation energy. The next diagram shows Maxwell-Boltzmann distribution curves for a fixed mass of gas at two temperatures T and T where T is about 10 C higher than T . The total area under the curve remains the same since there is no change in the number of particles present. So, I predict that in the experiment were the temperature is varied, the rate of reaction will go up as the temperature goes up. In the experiment where the concentration of the thiosulphate is to be varied, I expect the rate of reaction to go up as the concentration goes up. If the concentration doubles, I would expect the rate of reaction to double and if the concentration is zero I would expect the rate of reaction to be zero. In the graph showing temperature compared to rate of reaction, I would expect there to be negative correlation and in the graph showing concentration compared to rate of reaction, I would expect there to be negative correlation. However, it remains to be seen if the results will follow this theory. Here are the results tables that will be used: Temperature 1st results 2nd results Average Rate Of Reaction C seconds seconds seconds seconds Room approx.20 30 40 50 60 70 This is for the first half of the experiment where everything will be kept the same except the temperature which will range from 20 C to 70 C. It is hoped that there will be sufficient time for two experiments and an average will be calculated afterwards. The concentration of the sodium thiosulphate used throughout will be 30g/dm. Concentration 1st results 2nd results Average Rate Of Reaction g/dm seconds seconds seconds seconds 15 20 25 30 35 40 This is the other section to the experiment where everything will be constant apart from the concentration of the sodium thiosulphate. It has been decided that a concentration of no less that 15g/dm will be tested because any less than this would probably take too long. The hydrochloric acid and the sodium thiosulphate will not be heated and the tests will be done at room temperature, usually around 20 C. The experiment will be done twice or three times if possible and the results will be made fair by the fact that only one thing will vary each time. Goggles and aprons will be worn at all times for safety. It has been decided that 5ml of HCl and 20ml of Na S O will be used. Obtaining Evidence These are the results of the experiments: Temperature 1st results 2nd results Average Rate Of Reaction C seconds seconds seconds secs Room approx.20 74.5 69.9 72.2 13.85 30 38.1 38.3 38.2 26.18 40 35.9 39.4 37.65 26.56 50 20.7 18.1 19.4 51.55 60 12.3 9.9 11.1 90.09 70 5.9 5.2 5.55 180.18 Concentration 1st results 2nd results Average Rate Of Reaction g/dm seconds seconds seconds secs 15 125.2 123.5 124.35 8.04 20 74.5 69.9 44.2 13.85 25 53.6 51.2 52.4 19.08 30 49.6 51.6 50.6 19.76 35 45.7 48.8 47.25 21.16 40 22.6 30.5 26.55 44.35 Analysing evidence and drawing conclusions All results have now been obtained and they seem to be quite good, all showing correlation. As was hoped at the start, a repeat was managed for each test and an average worked out from those figures. The results were recorded with decimal place and the averages and rate of reactions are to two decimal places. The rate of reaction is the key thing being looked at in this experiment and this is how it was calculated: 1 Time taken for cross to be obscured This figure was then multiplied by 1000 to make it easier to deal with. The figures have all been rounded to two decimal places. My predictions have been correct. When the concentration of the sodium thiosulphate has gone up, as the first part of the experiment shows, the rate of reaction goes up. When the temperature goes up, as the second results table shows, so does the rate of reaction. This is what was expected and therefore makes it highly unlikely that there have been any major mistakes, although all results are obviously not perfect. The next three pages are graphs. Graphs one and two relate to the first table of results and graph three relates to the second table. The reason there are two graphs for the first table is that one shows time taken for cross to be obscured and the other shows rate of reaction. Rate of reaction is what is being investigated and so only a rate of reaction graph was needed for table two. There are two graphs for the first results table to show the difference in time taken and rate of reaction i.e. the time taken for cross to be obscured shows negative correlation while graph two shows positive correlation. By drawing a line of best fit on the rate of reaction graphs, we can see that there are no results that are obviously completely wrong. With both graphs the last result is suprisingly high, and this can be seen on the results table as well. Evaluating Evidence The procedure used was good and produced good results but it could have been improved and these will be listed later. The results are mainly good, there are no odd results and everything came out as expected. This could mean that the experiment was done perfectly but it doesn't. Although all the average times and rates of reaction all conform to a pattern, they are not all evenly spaced and therefore are probably not perfect. As an example, in the first experiment, where the temperature was being varied, the rates of reaction of 30 C and 40 C were 26.18secs and 26.56secs respectively. This was only an increase of 0.38secs compared to an increase of 90.09secs for 60 C to 70 C from 90.09secs to 180.18secs . Clearly this is an enormous difference and disproportionate. The results could be correct but the results do appear to nearly double each time, except for in this instance. There are similar examples from the second experiment but they are not as obvious. Improvements that could be made if the experiment was repeated: When doing the results that took less time some took around five seconds, it would have been more accurate to have two people so one person could put the substances together while the other person started timing Obviously it would have been good to have done more repeats. Two tests were managed each time but if one had been wrong this could have dramatically changed the average time and therefore rate of reaction. Increasing the surface area of a reactant will increase the rate of a reaction. This is because the reacting particles can only collide with he surface of the solid and the particles within the solid cannot react until those on the surface have reacted and moved away. Powdered calcium carbonate has a much larger surface are than the same mass of marble chips and therefore will react more quickly. All in all I think this was a good experiment and the best that could have been done with the time and resources available. The results supported my predictions and they seem to be fairly reliable results. Aim : We did 4 experiments to find out how the rate of reaction changes with differing concentrations of Sodium Thiosulphate, Hydrochloric Acid and water. As an inert and stable liquid, water was used to alter concentration of Sodium Thiosulphate without changing the end amount of solution. All the atoms in a water molecule have a full outer shell, so they would not react with the other chemicals. WATER IS USED TO SLOW THE REACTION SO THAT IT IS EASIER TO TIME HOW LOG
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I am measuring the rate of reaction how fast a reaction takes of sodium thiosulphate and hydrochloric acid. There are different variables I could use to see the change in the rate of reaction. These include temperature, concentration or catalysts. I am going to do two experiments, one changing the temperature and one changing the concentration of the sodium thiosulphate. This is how they will be done. Planning Experimental Procedures Equipment Sodium thiosulphate Na S O of different concentrations Hydrochloric acid HCl Tile marked with a cross Measuring cylinder x2 Beaker...
supported my predictions and they seem to be fairly reliable results.

Aim : We did 4 experiments to find out how the rate of reaction changes with differing concentrations of Sodium Thiosulphate, Hydrochloric Acid and water. As an inert and stable liquid, water was used to alter concentration of Sodium Thiosulphate without changing the end amount of solution. All the atoms in a water molecule have a full outer shell, so they would not react with the other chemicals.

WATER IS USED TO SLOW THE REACTION SO THAT IT IS EASIER TO TIME HOW LOG

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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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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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