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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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Acid Limestone SC1 HF Planning...Acid Limestone SC1 HF Planning We are going to investigate the factors that affect the rate of a chemical reaction. Input Variables of this investigation I could study are: Amount of Calcium Carbonate CaCO3 Temperature of Acid Concentration of Acid molarity Surface Area Amount of Acid Gas Pressure The Variable I have chosen is the Concentration of Acid molarity. My prediction is that if the concentration of the acid increases there will be an increase in the rate of reaction for example the highest concentration will have the fastest reaction time with the Calcium carbonate to produce Carbon Dioxide. I think this will happen because activation energy is an amount of energy needed for a reaction to occur; this amount varies from different elements and type of reaction. This may save energy for industrial use, as they will only supply the amount of energy needed exactly and not more. The Collision Theory, from the kinetic theory of gases, the collision theory of bimolecular reactions in a gas phase was developed. In a reaction between two gaseous substances A&B a molecule of A must collide with B for the reaction to proceed but in a concentrated solution there will be a higher percent of reactants which will have no more energy. Not all collisions cause a reaction, only the ones which reach the activation energy of the reaction. If a solution is more concentrate it means there are more particles of reactant knocking about between the water molecules, which makes collisions between important particles more likely. In a gas, increasing pressure means the molecules are more squashed up together so there are going to be more collisions. Reactions only happen if the particles collide with enough energy. This is called initial energy, is known as the activation energy, and is needed to break the initial bonds shown in the diagrams below. The more often the particles collide and the harder they hit, the greater the reaction rate. This is why I predict that the rate of reaction will increase as the concentration of a solution increases. The higher the concentration of the hydrochloric acid is, the higher the chance of the bonds breaking because the stronger the hydrochloric acid is the more energy the molecules have so they travel with more force which means the bonds break. They get this energy from colliding with each other this is why the higher concentrated acids have more energy as they have more particles to collide with to produce energy. If the molecules do not have much energy they will just bounce of the bonds harmlessly. The energy is needed to break the bonds and get the reaction started. Rates of reaction can be changed not only by catalysts but also by changes in temperature and by changes in concentrations. Increasing the concentration can also increase the reaction rate by increasing the rate of molecular collisions. Image to show the collision theory and why by increasing the concentration of the acid the more likely the acid particles will hit the calcium carbonate bond in the correct place. The line has the classic shape of a rate of reaction graph. It starts off steep, becoming shallower until it levels off. You can tell the rate of reaction at any particular time by the slope gradient of the line. The word equation for this experiment is: CALCIUM CARBONATE + HYDROCHLORIC ACID=CARBON DIOXIDE+ WATER + CALCIUM CHLORIDE CaCO3 + 2HCl = CO2 + H20 + CaCl2 Fair Test Details The input Variable I am going to change is the concentration of acid. The variables I need to keep the same are: Amount of Calcium Carbonate CaCO3 Temperature of Acid Surface Area Amount of Acid Gas Pressure The outcome variable I am going to measure is the amount of Carbon Dioxide given off in 1 minute. The other outcome variables I could have measured are: How long it takes to produce 100ml of Carbon Dioxide, I have chosen the concentration of acid as my input variable as it is one of the easier variables to control, as variables like temperature and surface area are hard to either keep at a constant temperature or get the surface area the same each time you repeat the experiment. I will use the following equipment in my experiments: 10g-15g Marble Chips, 1 Conical flask, 1 Thistle Funnel, 25ml dilute Hydrochloric Acid, 1 Delivery Tube, 1 Gas Jar, 1 Bee Hive Shelf, 1 Measuring Cylinder, 1 Tub of water, 1 Bung, 1 Thermometer, 1 Greasy lid for gas jar, 1 Stopwatch, 1 Set of Scales, Distilled Water, 1 pair of Goggles, 1 Bench Mat, 1 Sieve. I will weigh out the marble chips on the scales so I have exactly the same mass of marble chips each time to make it a fair test. I will then place the chips in the conical flask, and place the airtight bung in the top so no Carbon Dioxide will escape making it a fair test. The bung will have the thistle funnel attached to it and the delivery tube. I will make sure the thistle funnel tube is touching the bottom of the flask so no carbon dioxide can escape that way. I will pour the 25ml of hydrochloric acid into the conical flask through the thistle funnel so that all the carbon dioxide is captured and non-can escape so it is a fair test. The carbon dioxide cannot escape through the thistle funnel, as the bottom of the tube will be submerged in acid if it is touching the bottom of the conical flask making it impossible for the gas to travel up it. The delivery tube will take the carbon dioxide produced up through the bee hive shelf and into the gas jar filled with water, as the carbon dioxide is produced it will push the water out of the jar and at the end of the experiment we can measure how much gas was collected by the amount of water we need to refill the gas tube to repeat the experiment. We will the gas jar to the top with water and then slide the greased lid across the top that makes sure the gas jar is full to the top. We will pull the end of the delivery tube up through the hole in the beehive shelf. The beehive shelf is then placed in the tub of water that goes about 4-5cm over the top of it. We will then put the gas jar with lid in the tub filled with water, we will then slide the greasy lid of the top and carefully keeping the top of the jar under the water place the open end of the jar on top of the beehive shelf over the top of the delivery tube so the carbon dioxide produced will be able to go straight into it, making it easier to record how much was produced. We use the measuring cylinder to measure how much water is needed to top up the gas jar after each experiment to wok out how much gas was produced. To make the measuring easier we can put an elastic band around the gas jar where the water level is at the end of each experiment so it is easier to measure. We will need the stopwatch to time the minute for the experiment so we will know when to stop the experiment and measure how much gas has been produced. I will use the Distilled water to dilute the acid to give me other concentrations to experiment with. I will try to take 4 "“ 5 readings for each concentration of acid as it will give us a clearer pattern and will make it easier to spot anomalous results so my average will be more accurate. I will use the concentrations of acid within the rage of 0.5m and 2m, as these are the acids available to us in school at the moment. I will be able to change the concentrations of the acids by diluting them with distilled water this will give us other concentrations giving us a wider range of concentrations to work with. I will make sure that I dispose of the left over marble chips correctly so the sink doesn't get blocked with the un-reactive pieces ate the experiment. I will make sure that the bung is on the conical flask securely in case of a violent reaction so it doesn't harm anyone. I will wear goggles to make sure that the acid doesn't go in my eyes. I will be careful when carrying or handling the glass equipment so not to drop it or cut my self with it. I will be careful when handling the acid, by not to using too much and making sure that any spills are mopped up straight away. I will make sure I keep an eye on my experiment so I get reliable results and also so it doesn't react to vigorously. Concentration of acid. M Amount of Carbon Dioxide produced in 1 min ml 1 2 3 4 5 Average 0.5 M 0.75 M 1 M 1.5 M 2 M Preliminary Work I hope to find out: How much Hydrochloric acid to use, What temperature is the best for getting my chemicals to react, How many grams of marble chips work best, How long too time for, for the best results i.e. 1 or 2 minutes. In my Preliminary work I took 0.5m acid and 2m hydrochloric acid as these are the highest and lowest concentrations of acids I am going to use. I did this to test to see how large a gas jar I needed and how easy it was going to be to carry out my experiment. I found that I needed a gas jar that could contain about a litre of water for my experiment as if the gas jar was any smaller the 2m acid would react to produce to much carbon dioxide to be measured accurately. I also found that the reaction wasn't as violent if I use only 20ml of acid instead of 25ml, this was enough to cover all of the marble chips but didn't produce to much carbon dioxide for me to measure. By using 15g of marble chips slowed down the rate of the reaction as there was more for the acid to react with which made the product easier to measure. Amount acid Concentration Result 25 ml 0.5 M 85 ml 25 ml 2 M Emptied gas jar. 20 ml 2 M 323 ml 20 ml 0.5 M 82 ml Obtaining Evidence Concentration of acid m Amount of Carbon Dioxide produced in 1 min ml 1 2 3 4 Average 0.5 M 40 ml 75 ml 76 ml 72 ml 74.33 ml 0.75 M 97 ml 115 ml 120 ml 105 ml 109.25 ml 1 M 190 ml 165 ml 157 ml 175 ml 171.75 ml 1.5 M 234 ml 200 ml 240 ml 221 ml 223.75 ml 2 M 225 ml 301 ml 320 ml 323 ml 314.66 ml Results from another group doing the same experiment using the same variable. Concentration of acid m Amount of Carbon Dioxide produced in 1 min ml 1 2 3 4 Average 0.25 M 23 ml 34 ml 19 ml 31 ml 26.75 ml 0.5 M 67 ml 75 ml 78 ml 64 ml 71.0 ml 1 M 169 ml 221 ml 175 ml 174 ml 172.66 ml 1.5 M 265 ml 276 ml 279 ml 273 ml 273.25 ml 2 M 383 ml 358 ml 370 ml 376 ml 376.33 ml Circled and pink results are the anomalous results, which are not included in the average. Analysis At the end of the experiment there was more gas produced by the 2m hydrochloric acids reaction than the 0.5m hydrochloric acids reaction. The higher the concentration of acid the faster the reaction and so more gas was produced in the minute. The lower the concentration of acid the less gas was produced, as the reaction takes longer. This is because a high concentrated substance has more particles, this means that the reaction is quicker because the reactant has more particles to collide with and so reacts faster. This happened because activation energy is an amount of energy needed for a reaction to occur; this amount varies from different elements and type of reaction. This may save energy for industrial use, as they will only supply the amount of energy needed exactly and not more. The Collision Theory, from the kinetic theory of gases, the collision theory of bimolecular reactions in a gas phase was developed. In a reaction between two gaseous substances A&B a molecule of A must collide with B for the reaction to proceed but in a concentrated solution there will be a higher percent of reactants which will have no more energy. Not all collisions cause a reaction, only the ones which reach the activation energy of the reaction. The higher the concentration of the hydrochloric acid is, the higher the chance of the bonds breaking because the stronger the hydrochloric acid is the more energy the molecules have so they travel with more force which means the bonds break. They get this energy from colliding with each other this is why the higher concentrated acids have more energy as they have more particles to collide with to produce energy. If the molecules do not have much energy they will just bounce of the bonds harmlessly. The energy is needed to break the bonds and get the reaction started. Rates of reaction can be changed not only by catalysts but also by changes in temperature and by changes in concentrations. Increasing the concentration can also increase the reaction rate by increasing the rate of molecular collisions. If a solution is more concentrate it means there are more particles of reactant knocking about between the water molecules, which makes collisions between important particles more likely. In a gas, increasing pressure means the molecules are more squashed up together so there are going to be more collisions. Reactions only happen if the particles collide with enough energy. This is called initial energy, is known as the activation energy, and is needed to break the initial bonds. The more often the particles collide and the harder they hit, the greater the reaction rate. If the experiment is completed with a high concentrated acid, the hydrogen is evolved much more quickly, making the liquid fizz. This is because the rate of reaction depends upon how frequently the molecules of the reacting substance collide. The concentrated acid has more molecules for a given volume than the more dilute acid. This is because there are more molecules about, the frequency of the collisions is greater, and the reaction is faster. Both of my graphs and my hypothetical graph from my plan show me that the higher the concentration of the acid the faster the reaction and the more product is produced in the time given. On the graph to show my results I have one anomalous result, this is at 1m of acid, but apart from this the rest of my results fit into my best-fit curve. All my graphs are of a similar nature and show the same thing this makes me confident in my readings. Evaluation For each concentration of acid the results seemed to come out close together which gave me confidence. I found it difficult to make accurate readings as gas could easily escape as not all of the equipment was as air tight as it could have been and I could have made silly mistakes as we were pushed for time and so we rushed a bit while carrying out the experiment. There are two reasons why I thought my results wee accurate. Firstly in most cases the amounts of Carbon Dioxide given off during the reactions were quite close together. Secondly the graph shows a clear pattern showing the different amounts of Carbon Dioxide produced for each concentration of acid. I spotted two anomalies which I ringed but ignored these when working out the averages, for my results and the other groups results which are included in my obtaining evidence. Taking 4 readings allowed me to even out the difficulties of measuring the amount of Carbon Dioxide produced in a minute for each concentration of acid, as it was difficult to pull the delivery tube out of the gas jar exactly after one minute, also gas could have been lost through the thistle funnel and through the gap between the bung and the conical flask or any other air tight materials these were all slight human errors which could have caused some of my anomalous results. The method worked quite well because most results seemed consistent. There were a few problems capturing the gas accurately because it was difficult to prevent leaks in the equipment if there were any. Sometimes the acid didn't cover all of the limestone, so I would have to next time make sure I choose flatter pieces of limestone to make sure it was all covered by the acid. Also the conical flask that the reaction was taking place in was getting slightly warm after each experiment this may have changed my results slightly. I would use a different conical flask each time to prevent temperature rise if I repeated the experiment. The fastest concentration of acid to react was the highest concentrated. The graphs show this clearly. The one 'odd' result ringed at 1 m acid on the graph was over average. This may have occurred by an inaccurate reading or by mixing unevenly as I may have mixed some acids more or less than others. However ignoring this, the other readings were consistent. The results covered a wide range of the concentrations available to us and agreed with the results of the rest of my class, who tried out different concentrations of acid. There are several ways I could improve the way the gas is collected. There are several ways in which this experiment can be extended. The surface area of the limestone used could be used, but would be very time consuming as each time the experiment was repeated we would need to make sure that the limestone was ground to the same size each time otherwise this would not be a fair test. Temperature could be altered to extend this experiment, but I would have to be careful when heating the acid not to go above 70°c as above this temperature the acid starts to decompose. Similar equipment would be needed for both of these experiments, for the surface area of the limestone we would need to use a mortise and pestle to grind it up to different surface areas, for the temperature variable we would have to use ice and a Bunsen burner to establish different temperatures. As one the products, is in the form of gas, another way of extending the experiment is to use different reactants and keep the variables the same, as you can control the concentration of the substrate and collect the gas given off from the reaction between the substrate and the enzyme. The volume of the product can be measured to demonstrate the difference of the reaction when certain factors are changed. Enzymes are made to e specific; this means that they can have only one substrate that they will wok on. Each enzyme has an active site that is where their own specific substrate's molecules will fit. Enzymes all work best at optimum temperature that is usually body temperature at 37°C. If the temperature that the enzyme has to work at gets to high, normally 40°C it will start to become denatured and therefore no longer wok on it's substrate as the active site has changed shape. Also enzymes usually wok best at an optimum pH level, this is normally seven because enzymes are proteins, which are damaged by very acidic or very alkaline conditions. Most reactions work better at higher temperatures, this is because molecules move around much quicker. This makes the molecules have more chance to collide with the substrate. With more collisions there is more chance of a reaction-taking place. This makes the rate of reaction faster. At 40°C the enzymes start to get damaged, this slows down reaction and by around 60°C the enzyme will be completely destroyed. SUBSTRATEGLUCOSE SOLUTION + EMZYMEYEAST GAS PRODUCTCARBON DIOXIDE + LIQUID PRODUCTALCOHOL + CHEMICAL PRODUCT + ENERGY   

Acid Limestone SC1 HF Planning We are going to investigate the factors that affect the rate of a chemical reaction. Input Variables of this investigation I could study are: Amount of Calcium Carbonate CaCO3 Temperature of Acid Concentration of Acid molarity Surface Area...

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Rate Of Reaction in... Rate Of Reaction in Sodium Thiosulphate and HCl Plan in this experiment I am investigating the rates of reaction, and the effect different changes have on them. The rate of reaction is the rate of loss of a reactant or the rate of formation of a product during a chemical reaction. A rate of reaction is measured by dividing 1 by the time taken for the reaction to take place. There are five factors which affect the rate of a reaction, by the collision theory of reacting particles: temperature, concentration of solution, pressure in gases, surface are of solid reactants, and catalysts. Aim: - my aim is to see the effects of a change in temperature and concentration on the rate of a reaction. The reaction that will be used is: Sodium Thiosulphate + Hydrochloric Acid Na2S2O3 aq + 2HCl aq Sodium Chloride + Water + Sulphur Dioxide + 2NaCl aq + H2O l + SO2 g + Sulphur S s Two experiments will be carried out "“ one changing the temperature while everything else remains constant and one varying the concentration while keeping everything else constant. Both the sodium thiosulphate and the Hydrochloric acid are soluble in water, so the concentration of either can be changed. temperatures and concentrations to use during my preliminary series of experiments "“ 50cm3 of sodium thiosulphate solution and 5cm3 of hydrochloric acid as the experiment one con 1 mol/dm3 of HCl acid concentration will be fixed 10-35g/dm3 of sodium thiosulphate all of these concentrations will be tested in turn going up in steps of 5g/dm3 20-70°C temperature all of these temperatures will be used going up in steps of 10°C Concentrations of 5, and 40 g/dm3 of thiosulphate were available to me but my preliminary work showed that the 5 g/dm3 and 40g/dm3 were too slow and fast respectively in reacting to be worth testing. Similarly any temperature below 20°C reacted too slowly, and 80°C and 90°C reacted too quickly to be worth including in my final results. Using my preliminary experiments I decided on using the following apparatus: 1 thermometer 1 beaker 2 measuring cylinders 1 conical flask 1 tripod 1 gauze 1 heatproof mat 1 stopwatch 1 Bunsen burner X board 1 pair of tongs 1 pair of goggles 1 apron Method: - Experiment 1 - Changing the concentration 5 cm3 of HCl at concentration 1 mol./dm3 and 15 cm3 of sodium thiosulphate at varying concentrations "“ 10 to 35 g/dm3 are poured out into two measuring cylinders and then poured into a conical flask, which is placed on top of a board marked with letter X. The stopwatch will now be started. When the mixture has turned sufficiently cloudy so that the letter X can no longer be seen the stopwatch will be stopped and the time will be recorded. The experiment is repeated with all the concentrations. The whole procedure is then repeated. Experiment 2 "“ Changing the temperature 5 cm of HCl at concentration 1 mol./dm3 and 15 cm of sodium thiosulphate at varying concentrations "“ 10 to 35 g/dm3 are poured out into two measuring cylinders. A beaker is half filled with hot water from a tap. The water is placed on top of a Bunsen on a blue flame and the two measuring placed inside the water bath. The water is heated to the necessary temperature 30°C to 70°C then the two measuring cylinders are taken out and the contents of both are poured into a conical cylinder. The time it takes for the X to disappear is timed and recorded. The experiment is repeated using all the temperatures. The entire procedure is the repeated. Repeat results and averages will be taken to improve the credibility of the findings, and present solid grounding for the final conclusion. The repeat results will help to iron out any anomalies and the average will give a good summary of the results of the experiment. However if one set of results is entirely different to the other, a third experiment will be performed to replace the anomalous set of results. Safety "“ A pair of goggles will be worn during the heating part of the experiment in order to protect the eyes. An apron will also be worn to protect the skin and clothing. When handling hot beakers and measuring cylinders a pair of tongs will be used. A gauze and heatproof mat will be used while heating to avoid any damage to the equipment. Fair Test - In order for my findings to be valid the experiment must be a fair one. I will use the same standard each time for judging when the X has disappeared. I will make sure that the measuring cylinders for the HCl and thiosulphate will not be mixed up. The amount of HCl will be 5 cm3 each time, and the amount of thiosulphate will be fixed at 15 cm3. During the heating stage of the experiment, a blue flame will be used throughout. Also the same Bunsen burner and gas tap will be used to maintain continuity. All of these precautions will make my final results more reliable and keep anomalies at a minimum so thus make the entire investigation more successful. Prediction "“ I predict that as the temperature is increased the rate of reaction will increase. I also predict that as the concentration of the sodium thiosulphate increases the rate of reaction will increase. This means that both graphs drawn up in my analysis will have positive correlation, and will probably be curved as the increase in rate of reaction will not be exactly the same as the concentration temperature is increased. This can be justified by relating to the collision theory. When the temperature is increased the particles will have more energy and thus move faster. Therefore they will collide more often and with more energy. Particles with more energy are more likely to overcome the activation energy barrier to reaction and thus react successfully. If solutions of reacting particles are made more concentrated there are more particles per unit volume. Collisions between reacting particles are therefore more likely to occur. All this can be understood better with full understanding of the collision theory itself: For a reaction to occur particles have to collide with each other. Only a small percent result in a reaction. This is due to the energy barrier to overcome. Only particles with enough energy to overcome the barrier will react after colliding. The minimum energy that a particle must have to overcome the barrier is called the activation energy, or Ea. The size of this activation energy is different for different reactions. If the frequency of collisions is increased the rate of reaction will increase. However the percent of successful collisions remains the same. An increase in the frequency of collisions can be achieved by increasing the concentration, pressure, or surface area. Concentration "“ If the concentration of a solution is increased there are more reactant particles per unit volume. This increases the probability of reactant particles colliding with each other. Pressure - If the pressure is increased the particles in the gas are pushed closer. This increases the concentration and thus the rate of reaction. Surface Area "“ If a solid is powdered then there is a greater surface area available for a reaction, compared to the same mass of unpowdered solid. Only particles on the surface of the solid will be able to undergo collisions with the particles in a solution or gas. The particles in a gas undergo random collisions in which energy is transferred between the colliding particles. As a result there will be particles with differing energies. Maxwell-Boltzmann energy distribution curves show the distribution of the energies of the particles in a gas. The main points to note about the curves are: 1. There are no particles with zero energy. 2. The curve does not touch the x-axis at the higher end, because there will always be some particles with very high energies. 3. The area under the curve is equal to the total number of particles in the system. 4. The peak of the curve indicates the most probable energy. The activation energy for a given reaction can be marked on the distribution curve. Only particles with energy equal or greater than the activation energy can react when a collision occurs. Although Maxwell-Boltzmann distribution curves are for the particles in a gas, the same distributions can be used for the particles in a liquid or solid. Effects of a temperature change - The graph below shows Maxwell-Boltzmann distribution graphs for a fixed mass of gas at two temperatures "“ T1 and T2, where T2 is roughly 10°C higher than T1. The total area under the curve remains the same, since there is no change in the number of particles present. A small increase in temperature causes significant changes to the distribution energies. At the higher temperature: 1. The peak is at a higher energy. 2. The peak is lower. 3. The peak is broader. 4. There is a large increase in the number of particles with higher energies. It is the final change that results increase in rate, even with a relatively small increase in temperature. A small increase in temperature greatly increases the number of particles with energy greater than the activation energy. The shaded areas on the energy distribution curves show this. Effect of a catalyst - A catalyst works by providing an alternative reaction pathway that has lower activation energy. A catalyst does not alter the Maxwell-Boltzmann distribution. Because a catalyst provides a reaction route of lower activation energy, however, a greater proportion of particles will have energy greater than the activation energy. Secondary Sources Used: AS Level Chemistry Textbook kinetics module The Internet Dr. Jones's Chemistry Lessons Information sheets from Dr. Jones Obtaining Evidence Temp.°C Time 1 s Time 2 s Average s 20 110.67 107.42 109.045 30 100.13 103.34 101.735 40 64.20 65.92 65.06 50 45.34 37.73 41.535 60 30.12 33.18 31.65 70 18.92 16.34 17.63 Concen.g/dm3 Time 1 s Time 2 s Average s 10 222.63 224.38 223.505 15 150.90 147.03 148.965 20 105.25 105.97 105.61 25 66.04 68.75 67.395 30 55.63 56.1 55.865 35 27.32 25.96 26.64 Temp.°C Rate of Reaction 1s-1 Rate of Reaction 2 s-1 Average s-1 20 0.00904 0.00931 0.00917 30 0.00999 0.00968 0.00983 40 0.01558 0.01517 0.01537 50 0.02206 0.02650 0.02428 60 0.03320 0.03014 0.03167 70 0.05285 0.06120 0.05703 Concen.g/dm3 Rate of Reaction 1s-1 Rate of Reaction 2 s-1 Average s-1 10.00000 0.00449 0.00446 0.00447 15.00000 0.00663 0.00680 0.00671 20.00000 0.00950 0.00944 0.00947 25.00000 0.01514 0.01455 0.01484 30.00000 0.01798 0.01783 0.01790 35.00000 0.03660 0.03852 0.03756 Temp.°C Rate of Reaction 1s x1000 Rate of Reaction 2 s x1000 Average s 20 9.04 9.31 9.17 30 9.99 9.68 9.83 40 15.58 15.17 15.37 50 22.06 26.50 24.28 60 33.20 30.14 31.67 70 52.85 61.20 57.03 Concen.g/dm Rate of Reaction 1s x1000 Rate of Reaction 2 s x1000 Average s 10 4.49 4.46 4.47 15 6.63 6.80 6.71 20 9.50 9.44 9.47 25 15.14 14.55 14.84 30 17.98 17.83 17.90 35 36.60 38.52 37.56 Analysis In this experiment I have found that as the temperature and concentration is increased the time taken for the reaction to take place decreases. This means the rate of reaction increasers as it takes less time for a reaction to take place, so more take place per second. In the temperature experiment the time taken for a reaction to take place decreased by roughly 10 to 15 seconds for every 10°C increase in temperature, with the one anomaly being the 30°C reading. There is also a trend in the increase in rate of reaction as the temperature increases. The difference is always more or less 0.02 s-1, with the same exception. Using the graphs, with lines of best fit, I can draw a conclusion from my experiment. Firstly I can see that with the "time" graphs that plot temperature and concentration against time taken for the reaction to take place the graphs have negative correlation in both cases, meaning that as the temperature concentration increased the time taken for the reaction to take place decreases. The time graph for the temperature experiment has a much steeper curve than the one for the concentration experiment, meaning that the decrease in time taken for the reaction was far more rapid. Naturally, the above means that the both the graphs plotting rate against temperature and concentration have positive correlation "“ as the temperature and concentration are increased so does the rate of reaction. This is because when the temperature is increased the particles will have more energy and thus move faster. Therefore they will collide more often and with more energy. Particles with more energy are more likely to overcome the activation energy barrier to reaction and thus react successfully, and when solutions of reacting particles are made more concentrated there are more particles per unit volume. Collisions between reacting particles are therefore more likely to occur. The graph for concentration shows that when the concentrations were relatively low 10, 15, 20 g/dm3, the increase of rate x1000 was also fairly small increasing from 4.47 to 6.71 to 9.47. There was then a gradual increase in the difference, and between 30 and 35 g/dm3 the rate more than doubled from 17.90 to 37.56s-1. This shows that there are far more collisions at a concentration of 35 g/dm3 than at 30 g/dm3. The graph plotting time against the rate of reaction x1000 shows that the difference of rate between increasing temperatures excluding the anomaly of 30°C was pretty much regular, increasing in steps of 6-10 9.17 to 15.37 to 24.28 to 31.67. However, once again there is a giant gap in the last temperature increase "“ at 60°C the RoR x1000 is 31.67 s-1, and at 70°C it is 57.03 s-1. For this to fully make sense it is necessary to recap the collision theory briefly: For a reaction to occur particles have to collide with each other. Only a small percent result in a reaction. This is due to the energy barrier to overcome. Only particles with enough energy to overcome the barrier will react after colliding. The minimum energy that a particle must have to overcome the barrier is called the activation energy, or Ea. The size of this activation energy is different for different reactions. If the frequency of collisions is increased the rate of reaction will increase. However the percent of successful collisions remains the same. An increase in the frequency of collisions can be achieved by increasing the concentration, pressure, or surface area.   

Rate Of Reaction in Sodium Thiosulphate and HCl Plan in this experiment I am investigating the rates of reaction, and the effect different changes have on them. The rate of reaction is the rate of loss of a reactant or the rate of formation of...

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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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RATES OF REACTION SKILL... RATES OF REACTION SKILL P  There are four factors that affect the rate of a chemical reaction. These are Temperature, Surface area, concentration and the use of catalysts.  I am going to investigate the factors that affect the rate of reaction between marble chips and dilute Hydrochloric acid. The chemical reaction for this is : - CaCO3 S + 2HCL aq CaCL2 aq + H2O l + CO2  The factors that affect this reaction are: - Temperature: - In a cold reaction mixture the particles are moving quite SLOWLY "“ the particles will collide with each other less often, with less energy, and less collisions will be successful. If we heat the reaction mixture the particles will move more Quickly "“ the particles will collide with each other more often, with grater energy, and more collisions will be successful. The more the collisions the faster the rate of reaction.The reactant is broken down faster Surface area: - Large particles have a small surface in relation to their volume "“ fewer particles are exposed and available for collision. This means fewer collisions and a slower reaction. Small particles have a large surface area in relation to their volume. "“ More particles are exposed and available for collision. This means more collision and a faster reaction. The reactant is broken down faster Concentration: - In a reaction where one or both reactants are in low concentrations the particles are spread out and will collide with each other less often resulting in fewer collisions. In a reaction where on or both reactions are in high concentrations the particles are crowded close together and will collide with each other more often, resulting in an increased number of successful collisions. The more the collisions the faster the rate of reaction. . The reactant is broken down faster Plan of carrying out investigation  To make this a fair test we tried to keep the weight of the marble in each investigation the same.  With my partner we investigated the factor of concentration.  We were provided with marble chips of masses in the range of 0.3 "“ 0.6g and 2 mol dm ¯ ³  Firstly we set up the apparatus as shown on the next page. For our reaction we used 0.4g of marble chips and 10 cm³ of Hydrochloric acid in our first experiment and 6 cm³ of Hydrochloric acid 4cm³ water in our second experiment. Once everything was ready we started the investigation. To measure the difference between the two experiments we measured Carbon Dioxide levels. This was done using a gas syringe shown in the set-up on the next page. We recorded our results into tables every ten seconds writing down the amount of CO2 in cm ³. We did this experiment as efficiently as possible using equipment such as stop watches to make our results as exact as possible. We also wanted to keep the experiment safe so we wore safety glasses.  One of the most important equipment in the investigations was the gas syringe. After all this equipment allows us the progress of the investigation accurately. The gas syringe is connected to the test tube by an air tight rubber tube. Because the investigation is air tight, when the reactant reacts with the hydrochloric acid it produces the gas Carbon Dioxide, once produced it pushes the syringe forward and we can measure the rate of reaction.  We started the reaction by placing the marble chip in with the hydrochloric acid and covering the test tube with a bung. We realised that the reaction was over by recognising identical reading in three times.  To get the best results from the investigation we must repeat it several times so that we can average the results to ensure good results.   

RATES OF REACTION SKILL P  There are four factors that affect the rate of a chemical reaction. These are Temperature, Surface area, concentration and the use of catalysts.  I am going to investigate the factors that affect the rate of reaction between marble chips...

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