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Rates of reaction Plan Aim: In this experiment I will find the rate of reaction between Sodium thiosulphate NaS2o3 and Hydrochloric acid HCl. There are different variables I could use to see the change in the rate of reaction. These include temperature, concentration or catalysts. I will investigate how temperature affects the rate of reaction between Sodium thiosulphate and Hydrochloric acid. Prediction When sodium thiosulphate and hydrochloric acid react they produce a cloudy precipitate. The two chemicals are both clear solutions and will react together to form a yellow precipitate of sulphur, the equation for which is as follows: NaS2O3 aq+ HCll¨Sg+NaCls+ H2Ol+SO2s As the solution will turn cloudy, we can observe the rate of reaction by placing a black cross underneath the beaker and seeing how long it takes for it to disappear. There are factors that affect this experiment such as temperature, concentration and time. I do not think that surface area will affect the experiment, as both chemicals are liquids. For my experiment I will study temperature as this is easily observed and can be easily varied. I think that as the temperature of sodium thiosulphate increases, the amount of time taken for a reaction decreases. I know this because before two particles can react they must meet. The higher the temperature there is the more successful collisions between other particles is increased. When temperature increases the bonds in NaS2O3 break quicker because more energy is available greater than the activation energy of the reaction. As a result S2O3 2- ions are available so it takes less time to bond with H+ ions from HCL and new bonds are formed quicker and therefore sulphur precipitates quicker and the rate of reaction increases. S2o3 2- aq +2H+ aq S02aq+Sg+H2Ol When the temperature increases it causes an increase in kinetic energy so you have more chances of successful collisions between NaS2O3 particles and HCl particles so the rate of reaction increases. Also more activation energy is made available to overcome the activation energy of the reaction; the reactants have greater energy than the activation energy, so the reaction takes place quicker. I will keep the concentration of NaS2O3 constant to prevent more successful collisions as there would be more particles available if a higher concentration is fed which will increase successful collisions. I will also keep the concentration of HCl constant as an increase or decrease in concentration will affect the rate of reaction. I will change the temperature of NaS2O3 so I can see how the temperature affects the rate of reaction. I will keep the temperature of the HCl acid at room temperature as we are only concentrating on the NaS2O3 and if we heat the HCl it might affect the rate of reaction it would not be a fair test if we heat the HCl when we are observing how NaS2O3. I also predict that every time the temperature increases by 10oC the rate of reaction doubles. The preliminary results Time on heat sec Temperature of NaS2O3 0C Time taken for cross to disappear sec 0 24 60 10 34 52 Method For the preliminary experiment I heated the NaS2O3 to get it to the temperature I wanted but it was difficult to get the NaS2O3 to the right temperature so the results were not as accurate, but for my real experiment I will use a water bath to get accurate results instead of a Bunsen burner. For the preliminary experiment I only recorded the temperature of the NaS2O3 but for my real experiment I will record the temperature of the HCl as well to get more accurate results because if the NaS2O3 was high and the HCl could bring the temperature down quicker and also have to make sure all the temperature of the HCl is the same. I will also take the temperature of the mixture so I know the temperature at which the reaction took place. 1. I will set up my apparatus and put an X on a piece of paper and measure out 50ml of NaS2O3 and 10ml of HCl. 2. I will pour the NaS2O3 into a conical flask and measure the temperature and pour the HCl in to the same conical flask and time how long it will take for the cross on the paper to disappear. 3. I will do 4 different temperatures and I will do them three times each to get accurate results. 4. I will record the results in a table of results. Apparatus used Sodium thiosulphate NaS2O3-50ml Hydrochloric acid HCl-1M Conical flaskx2 Measuring cylinderx2 Thermometer Water bath at different temperatures Paper marked with X Stop watch Distilled water Analysis From graph 1 I can see that when temperature increases the time taken for reaction to take place decreased. In graph 2 I can see when temperature increases the rate of reaction increases. There was an anomalous result in graph 2, when the temperature was 480C and 1€time was 1.18. My results agree with my prediction because I predicted that the higher the temperature the lower the time taken for the reaction to take place and we can see this from the graphs. The graph shows this pattern taking place. For my experiment I studied temperature as this is easily observed and can be easily varied. The temperature of sodium thiosulphate increased, and the amount of time taken for a reaction decreased. When temperature increased the bonds in NaS2O3 broke quicker and more energy is available greater than the activation energy of the reaction and S2O3 2- ions are available so it takes less time to bond with H+ ions from HCl and new bonds were formed quicker and therefore sulphur precipitated quicker and the rate of reaction increased. This is why in graph 2, I had a strait line positive correlation graph. When the temperature increased it caused an increase in kinetic energy so we had more successful collisions between NaS2O3 particles and HCl particles and the rate of reaction increased. Also more activation energy was made available to overcome the activation energy of the reaction; the reactants had greater energy than the activation energy, so the reaction took place quicker. I think my results support my prediction because I predicted when temperature increases the rate at which the reaction takes place is faster. In graph 2, the theory that every time the temperature increases by 10oC, the rate of reaction will double did not work in my experiment and the results of that theory is given below: 10"¹C¨0.018 0.024€0.018=1.333 20"¹C¨0.024 0.052€0.024=2.167 30"¹C¨0.052 0.078€0.052=1.500 40"¹C¨0.078 0.086€0.078=1.103 50"¹C¨0.086 0.104€0.086=1.209 60"¹C¨0.104 0.120€0.104=1.154 70"¹C¨0.020 0.1380.120=1.1500 80"¹C¨0.138 Evaluation I think my method worked well as I repeated the experiments three times for five different temperatures and got three results which were similar. I think the experiment worked but when we used NaS2O3 with a high temperature, it was difficult for us to time the reaction as it was more rapid than we had expected. If I had the chance to repeat the experiment I would concentrate on the concentration of the NaS2O3 rather than the temperature as there are a lot of factors which could affect the temperature. I think my experiment was done reasonably well as l got similar results when I repeated them three times. There was one anomalous result in graph 2 and I think there was an anomalous result because the NaS2O3 was at a high temperature and the reactants reacted rapidly that the timing was wrong. I also think this was caused by the open window we worked next to which brought the temperature down quickly. I think my results are fairly reliable and it supports my analysis as I said, when temperature increased the time taken for the reaction to take place decreased. I could try the experiment with different methods and different reactants to get additional knowledge. I could use magnesium instead of Sodium thiosulphate and I could heat the hydrochloric acid instead of heating the NaS2O3 and to make more of a fair test I could make sure all the windows and doors are closed and no cold air comes in.
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Rates of reaction Plan Aim: In this experiment I will find the rate of reaction between Sodium thiosulphate NaS2o3 and Hydrochloric acid HCl. There are different variables I could use to see the change in the rate of reaction. These include temperature, concentration or catalysts. I will investigate how temperature affects the rate of reaction between Sodium thiosulphate and Hydrochloric acid. Prediction When sodium thiosulphate and hydrochloric acid react they produce a cloudy precipitate. The two chemicals are both clear solutions and will react together to form a yellow precipitate of sulphur, the equation for...
worked next to which brought the temperature down quickly. I think my results are fairly reliable and it supports my analysis as I said, when temperature increased the time taken for the reaction to take place decreased.

I could try the experiment with different methods and different reactants to get additional knowledge. I could use magnesium instead of Sodium thiosulphate and I could heat the hydrochloric acid instead of heating the NaS2O3 and to make more of a fair test I could make sure all the windows and doors are closed and no cold air comes in.

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My aim is to... My aim is to find out whether temperature has an effect on a rate of the reaction. I am going to be using the example of the reaction between Sodium Thiosulphate and Hydrochloric Acid. Prediction I predict that the higher the temperature, the more quickly the reaction will occur. This is because with heat, the particles of sodium thiosulphate and hydrochloric acid have more energy. This causes them to move around more. It works like this for all substances, not just those two. Chemical reactions require collisions, and if particles are moving around more quickly they are obviously more likely to collide and, as Collision Theory states, it affects the energy of the collision. I found out from preliminary research that the particle theory explains that chemical reactions require a collision between the particles of the reactants, at a certain speed and energy. I also found out that the factors that affect the rate of a reaction are:- § The surface area of the solid reactant if there is one § The concentration of the liquid substance. § The presence of a catalysts § The temperature In this experiment we are only interested in temperature. Where temperature is not high enough to provide energy for the particles to move at a high enough speed, the particles will just not react, and the higher the temp. the faster the particles move, so there are more collisions and so the faster the reaction will take place. At 20°C, I predict that the reaction will take a very long time to react. The reason I think this, is because although the particles will be moving around, they will not be moving at a high enough velocity for chemical reactions to occur, the particles must be travelling at a high speed and this requires energy. At this temperature I do not think that it will give the particles enough energy to convert into movement. At 30°C, I predict that the reaction will occur more quickly than that of 20°C. I predict this because there is more heat to provide energy to the particles of the reactants. This energy causes the particles of sodium thiosulphate and hydrochloric acid to move around more quickly, and naturally more collisions happen between the particles. Every jump upwards in the temperature of ten degrees I would expect the rate of the reaction to double. It should follow the Q10 rule. At the highest temperature of 60°c I would expect the reaction time to be very fast. I think this because the particles of sodium thiosulphate and hydrochloric acid will be moving around very quickly and at a high velocity so the chemical reaction will take place quicker. To summarise, at a cold temperature the reaction will take more time to happen. The particles of sodium thiosulphate and hydrochloric acid will not be moving around so quickly, meaning they are less likely to collide, therefore the reaction will take place in more time. Chemical reactions require a collision at a certain velocity, and if this velocity is not reached then the reaction will just not happen. With more heat, the particles have more energy, meaning they move around more. Collisions will be more likely to happen at a higher speed. Rate = Results. Temp. °C 20 30 40 50 60 Time s 1. 69 33 35 13 08 2. 62 32 35 12 12 3. 42 24 29 10 10 Average 65.5 32.5 29 11.66 10 Rate 0.015 0.030 0.034 0.085 0.100 Number = anomaly See graph 1.A Higher temperature has two effects: - - More collisions per second, - More energetic collisions. That's why a 10°C rise doubles the rate rather than double temp doubles rate. Conclusion I conclude that the temperature does affect rate of reaction "“ the higher the temperature the faster the rate of reaction. I can see this from my table the lowest temperature has the highest reaction time - 20°C took 57s "“ and the highest temperature has the quickest reaction time - 60°C took 10s. as my graph shows. The line of best fit goes up very steeply. This is because with more heat, the particles of sodium thiosulphate and hydrochloric acid have more energy. This causes them to move around more. Chemical reactions require collisions, and if two sets of particles are moving around quickly there will naturally be more collisions. However, the collisions require the particles to hit each other at a certain velocity, and if this velocity if not reached then the reaction will just not happen. So, at the higher temperatures, more of the particles were travelling at a high enough speed to collide and react. At the lower temperatures it was more difficult for the particles to collide. Particle theory says that for a chemical reaction to occur, there must be a collision at a certain velocity and at a certain angle. Also, the factors that affect the rate of a reaction are the surface area of the solid reactant if there is a solid reactant, the concentration of the aqueous reactant, the presence of catalysts and temperature. In this experiment we were concentrating on temperature, and we were able to draw the conclusion that temperature does, in fact, affect the rate of a reaction, in that when the temperature is higher the reaction takes less time. At 20°C the reaction took a long time to occur. This was because there was not very much heat. Heat provides energy to the particles of reactants, and if there is not very much heat, the particles do not have very much energy. Because they do not have much energy they will not move around much, and will therefore not collide very often. Chemical reactions require a certain speed collision to react, and at this temperature very few of the particles collided, because of not moving around more due to lack of energy, because the heat was not very great. Between 35-55°C the rate of reaction rises very dramatically. I can tell this from my graph, as the line of best fit goes up very steeply. See graph 1.b At 60°c the rate of reaction is at its highest as my graph shows, the best fit line is rising almost vertically. My results and evidence support my prediction very well. They prove the fact that temperature does affect the rate of reaction. I also have the particle theory to support my prediction and conclusion. Evaluation. I believe that the method we used was very good because we had one person using the syringe to mix the liquids together, we had one person timing and one person recording the results and checking the temperatures. I think this was a very good method because it makes the experiment very fair because the results we obtained are more accurate and fair than if we had used a different person each time for each thing. Also, we took great care in making sure that the measurements were as accurate as they could have been. Another reason our results are good is that we took multiple recordings and found the average for them, giving a more accurate result for each temperature. We may have timed one of the results wrong because it was a lot different from the other results, this is called an anomaly and we discarded it as it would have made the average lower than it should be. It is quite difficult to judge properly the exact moment that the cross disappears. It is even more difficult for the higher temperatures, as you would have to have an extremely good reaction time to stop the stopwatch exactly when the cross changes. However, our results were consistent. Although we did have one anomaly we made sure that the results were as accurate as they could have been. Concerning the amount of time taken for the cross to disappear, we could use a different method of working out how long the reaction took to occur. For example, we could shine a torch through the conical flask, and as soon as the light cannot shine through any more, we would stop the stopwatch. This would be one of the things I'd change if I did the experiment again in the future. For further work to our experiment, we could perform the experiment in a vacuum, as then there would be no other factors that can affect our results, other than temperature, which is the variable we wanted.   

My aim is to find out whether temperature has an effect on a rate of the reaction. I am going to be using the example of the reaction between Sodium Thiosulphate and Hydrochloric Acid. Prediction I predict that the higher the temperature, the more quickly the...

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HYPOTHESIS We can recognize four... HYPOTHESIS We can recognize four types of substances due to their structure: ionic, metallic, covalent, and molecular. If a given substance has a metallic luster, is malleable and ductile, is a good conductor of heat and electricity, and has high melting and boiling points, than it is supposed to be a giant metallic structure. If a given substance has low melting and boiling points and does not conduct electricity, it surely is a molecular structure. If a given substance is soluble in water and in other polar solvents, if it conducts electricity after being melted or dissolved, and if it has high melting and boiling points, we can predict that it is a giant ionic structure. So we will have to check which of these properties does a given substance have. APARATUS spatula stirring rod open electric circuit batteries, light bulb, electric wire with two dismantled endings two metal plates the first made of copper, the second made of zinc plastic wash bottle test tubes in amount of 4 watch glasses in amount of 5 Bunsen burner test-tube rack porcelain crucible crucible tongs triangle tripod I decided to use separate watch glass for each substance to avoid possible laboratory errors resulting from contamination with the previous one. CHEMICALS substance A "“ white, granulated powder substance E "“ silver nodules, apparent metallic luster substance C "“ tiny, white crystals substance D "“ a bit larger white crystals substance B "“ black powder distilled water SAFETY RULES Be careful while burning substances in a flame! Don't put your hand into water when the electric current flows "“ you can have your skin seriously damaged! Do not touch hot crucible with bare hand, use crucible tongs! PROCEDURE I put a few grams of each substance except for substance E, which I put into a watch glass using a spatula into separate test tubes, placed in a test tube rack. I put a hint of each substance into separate watch glass. I use open electric circuit in order to investigate electric conductivity of each substance in solid state. I pour a few droplets of water into each watch glass using plastic wash bottle. Then I mix each substance with a stirring rod in order to make process of dissolving faster and more effective. I put two metal plates into each watch glass, so they are partly sunk in the water or solution, if it was formed in the manner one ending of the electric wire sticks to the first plate, and the second ending sticks to the second plate, and it is important that plates do not touch each other. Then I observe whether the light bulb is shining. I take a hint of each substance one by one, using a spatula. I put each substance into a porcelain crucible. I put crucible on a triangle placed on a tripod above the Bunsen burner. Then I turn the burner on and wait up to a minute in order to check whether the melting point is low or high. To handle the crucible I use crucible tongs. Note: I carefully clean spatula before using it again and again, I do the same with the stirring rod and porcelain crucible. DATA COLLECTION A B C D E Conductivity in solid state - + - - + Conductivity after being dissolved - - + - - Solubility in water + - + - - Melting point low high high high high CONCLUSION Substance A is soft and granulated. This substance has low melting point, what indicates that the intermolecular forces are weak. It does not conduct electricity, because molecules are not charged. So substance A has undoubtedly molecular covalent structure. However, on contrary to other substances with molecular covalent structure, it is quite soluble in water, what means that its' molecules can form hydrogen bonds to the water to compensate for the water-water hydrogen bonds broken. Example of such molecules are sugar molecules, so this substance is probably sucrose. In the case of the substance E there is an apparent metallic luster, so it has the giant metallic structure. This metal has high melting point, because it takes a lot of energy to break up a lattice of ions in a sea of electrons with strong forces of attraction, called metallic bonds, between them. Metals are good conductors of electricity because the delocalized, free electrons can move through the lattice carrying charge, when a voltage is applied across the metal structure. The substance C is the only substance aqua solution of which conducts electricity, so it has to have giant ionic structure. It's because the water molecules, which are dipoles, can attract the ions away from the lattice. The ions move freely, surrounded by water molecules. Dissolved or melted ionic compound conducts electricity, because the lattice breaks up and the ions are free to move as charged particles. It can be assumed that substance D is a giant covalent structure, because it is insoluble, it is very hard, but brittle, it forms crystal lattice, and it has high melting point. In addition, this substance does not conduct electricity at all. Substance B is soft and brittle in touch - the sheets can slide over each other easily. It may indicate that this substance has a molecular structure, like the first one. But it has much higher melting point than molecular substances. Besides that, it conducts electricity in solid state, and it does not dissolve in water. This set of properties is very specific "“ it is a combination of single properties of different types of structures. The fact that this substance could well be used as a lubricant layers are easily rubbed off could indicate that this substance can be graphite. EVALUATION After an experiment was finished, our chemistry teacher wrote the names of substances that we were to determine structures of, on the blackboard, so we could verify if our findings were correct and propose improvements to the method in case they were not. And so: substance A appeared to be glucose, substance B "“ graphite, substance C "“ sodium chloride, substance D "“ silicon dioxide, and substance E "“ chromium metal. My predictions according to substance A appeared to be correct. In case of substance E, which is chromium metal, I also obtained correct results. I think that this substance, like it is in case of all metallic substances, has a structure very easy to determine experimentally, even, to say, with bare eye, because we know that metals are the only type of substances that perform a property called metallic luster. Other properties I observed also form a set of properties typical for metal, which is chromium in this case. I was right in case of substance C, which, as it appeared later, is sodium chloride, and sodium chloride is the most characteristic representative of ionic substances. My assumptions relating to substance D are also proved to be correct, since I know now that this substance was silicon dioxide, commonly occurring as quartz, being a good exemplification of properties connected with a giant covalent structure. In case of substance B, I was again right, due to the fact that this substance appeared to be graphite, as I have predicted. Graphite is another example of giant covalent structure, but, on contrary to silicon dioxide, it conducts electricity "“ this property is specific only for this particular substance.   

HYPOTHESIS We can recognize four types of substances due to their structure: ionic, metallic, covalent, and molecular. If a given substance has a metallic luster, is malleable and ductile, is a good conductor of heat and electricity, and has high melting and boiling points, than it is supposed to...

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

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

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