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Aim: To investigate the rate of reaction between Hydrochloric acid and marble chips. Background Knowledge: Factors that affect the rate of reaction between hydrochloric acid and marble chips or any other reaction are called variables. They are: ¨ The surface area of the chips Solids with a large surface area react faster than solids with a smaller surface area. This is due to the fact that if there is more area on the solid to react with the substance the reaction is able to occur much faster. Page 79 "“ GCSE Chemistry revision Guide This diagram shows a large particle small surface area and lots of small particles large surface area and how the particles can react with more area on the smaller pieces. ¨ The temperature of the acid The more heat particles have, the more energy they have. So if the particles have more energy they're going to move around faster. As they're moving around faster, there's more chance of collisions. So the higher temperature increases collisions therefore speeds up the reaction. Page 79 "“ GCSE Chemistry revision Guide This diagram shows the difference in movement between hot and cold particles. ¨ The concentration of the acid As the concentration increases, the rate of reaction increases. This, like the temperature of the acid, is based on the collision theory. The higher the concentration, the more particles therefore the more collisions so the reaction takes place faster. Page 79 "“ GCSE Chemistry revision Guide This diagram shows the movement and difference between a low concentration of particles and a high concentration of particles. ¨ Catalysts A catalyst speeds up a reaction. It does this by lowering the activation energy. The activation energy is what is needed to turn reactants marble chips into products hydrogen gas. To make reactants turn into products a sufficient amount of energy is needed to make the particles collide to start the reaction. This is activation energy and it gives an exothermic reaction the energy it needs to continue the reaction. Catalysts lower the activation energy so it is easier for particles to react so a lot more particles have enough energy to react, therefore, speeding up the rate of reaction. Page 79 "“ GCSE Chemistry revision Guide This diagram shows how a catalyst gives particles something to stick to, increasing the number of collisions. Page 80 "“ GCSE Chemistry revision Guide This graph shows the effect of a catalyst on the rate of reaction. The factors that affect the rate of reaction are all based on the collision theory. The theory that all particles have to collide to cause a reaction. Preliminary work: To investigate the different concentrations of the acid would be the easiest to measure conducted over a short period of time and satisfactory results would be produced. To measure the rate of reaction, the amount of gas given off could be measured. From the equation: CaCO3 + 2HCL à CaCL2 + H20 + CO2 It is seen that a gas is produced, CO2 so the amount of gas that is produced at different concentrations could be measured. A mole calculation was used to find out how much Calcium Carbonate to use. If I use a 100cm3 measuring cylinder to measure gas: 24000cm3 of gas is 1 mole of gas 100/24000 = 1/240 = 4.2 x 10-3 moles CaCO3 : CO2 1 : 1 1 mole : 1 mole 100g : 44g 4.2 x 10-3 m : 4.2 x 10-3 m 4.2 x 10-3 m x 100g = 0.42g 0.42g of calcium carbonate should produce 100cm3 of gas. Therefore, the minimum of calcium carbonate I will use to get sufficient results is 0.5g. I will be using five different concentrations of acid: 100%, 75%, 50%, 25% and 0%. So the amount I will use will be: 100% = 20cm3 HCL 0cm3 Water 75% = 15cm3 HCL 5cm3 Water 50% = 10cm3 HCL 10cm3 Water 25% = 5cm3 HCL 15cm3 Water 0% = 0cm3 HCL 20cm3 Water This is used as a control A 0% concentration will be used as a control to see if calcium carbonate would react with water or not. This would then make sure that the reaction only takes place if HCL is present. Prediction: The higher the concentration, the faster the reaction will occur. From background knowledge, it is known that a reaction will occur when particles collide, so the more particles there are the more collisions there will be. If there are more reactant particles per set volume higher concentration more collisions will occur per second, consequently, more particles reacting per second and the rate of reaction is increased. So for a lower concentration there will be less particles, so there will be less collisions therefore the reaction will be slower. Also the higher the concentration the more gas will be produced. This is because if there's more particles higher concentration reacting with the solid marble chips then the reaction will take place quicker. Consequently, the lower the concentration, the less particles to collide and start a reaction so less gas is produced. Equipment: · HCL · Water · Marble chips · Pessel and mortar · Stopwatch · Weighing scales correct to 2d.p. · Spatula · Water trough · Measuring cylinder x2 · Boiling tube with bung and pipe · Clamp stands x2 Method: To measure the rate of reaction, time how long it takes for the marble chips to react and measure the gas given off. To do this put a 100cm3 measuring cylinder in a water trough, with water inside it, held up by a clamp stand. Then put the pipe from the boiling tube under the measuring cylinder. The boiling tube with a pipe will be held by another clamp stand opposite the measuring cylinder. Crush the marble chips into powder with a pessel and mortar and measure out 0.5g of powder for each experiment with the weighing scales. Then, measure the amount of water and HCL needed with the second measuring cylinder. For each different concentration the exact same thing will be done. Put the HCL/Water solution into the boiling tube and make sure the pipe is under the measuring cylinder. After that pour the calcium carbonate powder into the solution, then start the stop clock and put the bung on the boiling tube the same time the calcium carbonate goes in. Then, every five seconds, measure how much gas has been produced using the scale on the measuring cylinder. Repeat the experiment three times for each different concentration and then take an average. Diagram: Chemistry for you page 190 This diagram is similar to the experiment conducted except a boiling tube held by a clamp stand with a pipe and bung was used instead of a flask. Fair test: · The marble chips are crushed to make sure the surface area is the same for each experiment because a larger surface area would take longer to react than a smaller one. So if all the chips are of the same surface area, then they will all react at the same speed, making it a fair test. · All the HCL will be of the same strength, as all experiments will use the same HCL from the same bottle. Stronger acid will speed up the rate of reaction. · The water and acid will be of the same temperature each time because temperature affects the rate of reaction. · After each experiment, the boiling tube will be cleaned properly to get rid of the acid and bits of Calcium carbonate so there's no extra acid or calcium carbonate in the next experiment. · The 100cm3 measuring cylinder will always be full to the top with water so that measurements will be fair. Safety: · To ensure that no acid gets into anyone's eyes, safety goggles will be worn. · Make other persons aware of harmful chemicals. HCL · Necessary medical equipment near by, e.g. eye wash. · Have a cloth or towel near by to clean up any spilt acid so it isn't hazardous to anyone around. Results: Amount of HCL cm3 Amount of water cm3 Gas produced every 5seconds cm3 Average 1st time 2nd time 3rd time 20 0 25 24 25 24.67 45 44 40 43.00 55 57 53 55.00 61 60 57 59.33 65 68 64 65.67 67 68 66 67.00 68 69 67 68.00 69 69 68 68.67 70 71 69 70.00 70 70 70 70.00 70 70 70 70.00 70 70 70 70.00 15 5 20 19 22 20.33 38 35 40 37.67 44 40 41 41.67 47 44 42 44.33 48 45 45 46.00 51 47 46 48.00 53 50 48 50.33 55 54 49 52.67 57 56 50 54.33 58 57 55 56.67 59 58 58 58.33 61 59 59 59.67 64 60 60 61.33 64 62 63 63.00 65 63 65 64.33 66 65 66 65.67 66 67 70 67.67 66 67 71 68.00 10 10 12 10 13 11.67 26 23 20 23.00 29 25 26 26.67 31 27 27 28.33 32 28 28 29.33 33 28 29 30.00 34 29 32 31.67 35 31 34 33.33 36 32 35 34.33 36 33 37 35.33 37 35 38 36.67 38 36 39 37.67 39 37 39 38.33 39 38 40 39.00 40 38 41 39.67 41 39 41 40.33 41 40 42 41.00 43 40 43 42.00 43 41 44 42.67 44 42 44 43.33 45 43 45 44.33 45 44 45 44.67 45 44 46 45.00 5 15 12 13 11 12.00 20 19 21 20.00 23 24 22 23.00 24 24 25 24.33 25 25 25 25.00 25 25 25 25.00 25 26 26 25.67 0 20 0 0 0 0 All results will be plotted on the same graph. This will then make it easier to analyze my results. The average amount of gas measured cm3 will be plotted against time seconds. Graph to show results: The graph was produced by hand and scanned into the word document. Analysis: All concentrations produced gas rapidly to begin with but the most rapid was the 100% concentration. This happened with all the different concentrations except they all started to increase with a steady rate at different times. 100% 30 seconds 75% 15 seconds 50% 10 seconds 25% 10 seconds From this we can see that the higher the concentration, the faster the reaction starts and the longer it continues rapidly. The graph indicates this in the linear gradient of the slope. As the reaction increases the gradient becomes steeper. This result supports the predictions made based on the collision theory. As there are more particles in a higher concentration, there are more collisions so the reaction is faster. When the graph became flat, it was shown that there was no more solid to react with the HCL saturation. The reactions all varied in how long the reaction took place for. 100% 60 seconds 75% 90 seconds 50% 115 seconds 25% 40 seconds The longest reaction was the 50% concentration. The graph shows this by the line leveling out for longer linear gradient. Although it was the longest reaction it didn't produce the most gas. It just produced gas very slowly as it was a low concentration, because there wasn't enough particles to react to make the reaction faster. So gas was produced but very slowly and not much of it. 100% concentration solution was over quickly again, shown by the line on the graph and produced a lot of gas; due to there being more particles to react with the solid marble chips. The 25% concentration however, took place over an even shorter time than the 100% concentration but a lot less gas was produced in the 25% concentration again, due to there not being many particles. The different concentrations also varied on how much gas was produced overall on average. 100% 70.00 cm3 75% 68.00 cm3 50% 45.00 cm3 25% 25.67 cm3 As predicted, the most gas was produced by the higher concentration and the least gas was produced by the lowest concentration. From the graph it can be seen that for different concentrations the amount of gas produced varies. This is due to there being more particles in a higher concentration to react with the solid marble chips. The results gained support the theory that the more concentration, the faster the reaction and the more gas is produced. This matches the predictions made. It is also seen that as the concentrations become less, gas is produced at a much slower, yet at a steady rate because of not having enough particles to react with the substance making the reaction slower. The conclusions and prediction are all based on the collision theory: All particles have to collide in order to react with one another. Evaluation: The method used for conducting the experiment was an effective one as: · It was easily done over the amount of time given in class to conduct the experiment. · It was simple and easy to repeat a lot of times to get enough results to calculate averages. · Produced sufficient results and were easy to present on a graph to compare. · It was a safe experiment. · It was an easy experiment to make sure everything was a fair test and accurate. If the investigation was to be done again, consideration may be given to repeating the test a few more times for each concentration to produce a better average. From the graph it can be seen that some of the concentrations don't level out. This is because for each concentration, each time the experiment was conducted; the gas stopped being produced at different times. So when the average was taken it didn't always show the gas had stopped being produced. So the graph doesn't always level off. Maybe if the gas produced every 5 seconds had been recorded more times, say 10 or 20, instead of 3, the graph would've leveled off. Another reason for this is maybe that the experiment wasn't left going for long enough and a few more bubbles of gas could've been recorded giving more accurate results. It is shown on the graph that the 50% concentration produced more than the 75% most probably because of the reason just mentioned. Even though the results weren't as accurate as they could've been for the reasons mentioned above, they still verified the predictions and conclusions made. Further experiments could be conducted to extend the work I have done. These could be to investigate the other variables in the same way I have conducted my experiment: · Surface area "“ different sizes of marble chips for each experiment. · Temperature of the acid "“ investigate a range of temperatures. · Catalysts "“ investigate the effect of a catalyst in an experiment. If then all these different factors were investigated, all the results could be put together to prove the conclusions further. Bibliography: Books: 1. Chemistry For You, National Curriculum Edition for GCSE "“ Lawrie Ryan Page 190 "“ diagram of experiment 2. Revision Guide for GCSE Double Science, Chemistry, Higher level "“ Richard Parsons Page 79 "“ diagrams to show how different variables affect the rate of reaction Page 80 "“ Graph to show the effect of a catalyst on the rate of reaction Websites: 1. http://www.revisioncentral.co.uk 2. http://www3.mistral.co.uk/cns/depts/science/sc1/GCSE/
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Aim: To investigate the rate of reaction between Hydrochloric acid and marble chips. Background Knowledge: Factors that affect the rate of reaction between hydrochloric acid and marble chips or any other reaction are called variables. They are: ¨ The surface area of the chips Solids with a large surface area react faster than solids with a smaller surface area. This is due to the fact that if there is more area on the solid to react with the substance the reaction is able to occur much faster. Page 79 – GCSE Chemistry...

Bibliography:

Books:

1. Chemistry For You, National Curriculum Edition for GCSE – Lawrie Ryan

Page 190 – diagram of experiment

2. Revision Guide for GCSE Double Science, Chemistry, Higher level – Richard Parsons

Page 79 – diagrams to show how different variables affect the rate of reaction

Page 80 – Graph to show the effect of a catalyst on the rate of reaction

Websites:

1. http://www.revisioncentral.co.uk

2. http://www3.mistral.co.uk/cns/depts/science/sc1/GCSE/

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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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I am measuring the... 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   

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...

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Intro In this experiment I... Intro In this experiment I am going to investigate the reaction of sodium thiosulphate thio and hydrochloric acid. There are four main factors that affect the rate of reaction. Temperature-You would have to have the EXACT temperature. Surface Area particle size - It's hard to do this one as it is a liquid state. Catalysts-Increase the rate of a chemical reaction- Concentration- This is the best way as its fair and a better experiment to do rather than any of the other main factors that affect rate and reaction. I have done a variety of experiments on rates of reactions such as the marble chip and gas syringe experiment which tested the effect on surface area. I have decided that concentration is the best way to measure rates of reaction in this experiment. When sodium thiosulphate reacts with an acid it should go cloudy and I then have to measure how long this reaction takes. In this experiment I am going to investigate the reaction of sodium thiosulphate thio and hydrochloric acid. Hydrochloric Acid Sodium Thiosulphate Sodium Sulphate & Sulphur Na2S2O3 aq Na2 SO3 aq + S s I am going to change the concentration of these experiments, by adding water to the thio to see if this affects the reaction. The total volume of the liquid will stay the same; only the concentration of the thio will vary. Prediction I predict that if I add water to the thio, the reaction will decrease in speed, and this will make the solution less concentrated. It will take longer for the cross to disappear the less concentrated it is. If you half the concentration of thio I think this will double the time of reaction. 2 1 In box number 1. There are fewer particles of acid therefore leading to a less reactive experiment, and in box number 2. There are many more acidic particles more concentration of acid leading to a much more reactive experiment. Collision theory For a reaction to take place, the particles of the substances that are reacting have to collide. If they collide, with enough energy then they will react. The minimum amount of kinetic movement energy that two particles need if they are going to react when they collide is called the activation energy. There are therefore two main ways of increasing the rate of a reaction: Increase the number of collisions The Higher the concentration the more collisions there are the lower the concentration the less collisions there are leading to a less reactive experiment. Increase the amount of movement kinetic energy so that more collisions lead to more reactions. Dilution of Sodium thiosulphate The smallest amount of time shows how fast the reaction took place The Longest amount of time shows how slow the reaction took place * Diagram of Apparatus Safety Issues These are the safety precautions that I have taken during this experiment: To wear Goggles during the pouring of the acids and solutions, as the there's always a risk of getting harmful solutions in your eyes or face. ALWAYS stand and not sit while in contact with acid. Concentrate!!!! When you don't concentrate things go wrong, so put all of your effort into the experiment. Chairs should be tucked in, out the way. All belonging such as bags and books should be cleared away of the experiment. Analysis I've drawn line graphs to show the results of the experiment, it shows that as the concentration is decreased it will take longer for the cross to disappear; this tells me that my prediction was correct. The Graphs Iv drawn are Lines of Best fit graphs as this way is the best way in order to show the results correctly. In my prediction I said that if I add water to the thio, the reaction will decrease in speed, and this will make the solution less concentrated. I said that it will take longer for the cross to disappear the less concentrated it is, I explained that if you half the concentration of thio it will double the time of the reaction. As the more particles there is the more reactive experiment, the fewer particles the less reactive experiment. The more concentrated the quicker the reaction the less concentrated the slower the reaction. When I examine my graphs I can see the same trend and pattern, as each line is best fit. My graphs show a line of best fit, this goes through many of the points of results. The shape is a curve with the largest concentration being 50cm3 and the smallest concentration being 10cm3. In my results the fastest time being"¦"¦"¦"¦"¦"¦"¦ seconds and the slowest time being"¦"¦"¦"¦"¦"¦"¦ seconds on the 1st set. In my quantitative 2nd prediction I said that if I half the concentration the time will double, looking at my results in the 1st experiment I looked at 20cm3 thio & 40cm3 and the times were"¦"¦"¦"¦"¦"¦"¦"¦"¦"¦"¦"¦"¦"¦"¦"¦"¦"¦"¦"¦"¦"¦"¦"¦"¦"¦"¦"¦"¦"¦"¦"¦"¦"¦"¦"¦. Evaluation On my line graph that I drew it shows that some results are odd compared to the other results which I have circled, this may be because of issues with the decontaminated equipment or the wrong measurement of acid and thiosulphate was not the same. Many things went wrong during the experiments and one was; getting the correct amount of solution therefore making it a fair test. Also another thing is that trying to press the STOP button on the stopwatch as sometimes you would press it a few seconds late, and we had to do the experiments again repeatedly to make sure we made the experiments as fair as possible. If I was do to the experiment again I would change a few things, such as I and the few other pupils concentration as we weren't concentrating enough a few times which would ruin the experiment and we would have to do it time and time again. Another point that could also have made the experiment 'unfair' was that the temperature varied which also made a big difference to the experiment as some days it would be colder or hotter than others. There are "¦"¦"¦"¦"¦"¦"¦"¦ anomalous results on my graphs. They are circled on the graphs If there were no odd results present this would either be because; I carried out the experiment VERY carefully and accurately making sure that I got all the measuring accurate. The possible reason for my results could have been because I didn't measure out the concentration accurate enough, or because I was not concentrating enough on what I was actually doing. What I found very difficult Judging whether or not the cross disappeared, because I had a different person judging each time and their opinion would be different to each others opinion. Making sure the stop watch was turned on and off at the right moment in time, because each second is very important and valuable. Measuring out the liquids because it had to be very accurate. What I need to improve Check the temperature does not change too much as this could change the results. If it's hotter the reactions would be faster and we are not measuring temperature we are measuring concentration. Keeping the same measuring cylinder.   

Intro In this experiment I am going to investigate the reaction of sodium thiosulphate thio and hydrochloric acid. There are four main factors that affect the rate of reaction. Temperature-You would have to have the EXACT temperature. Surface Area particle size - It's hard to do this one as...

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