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Risk Assessment To keep the experiment safe I shall keep electrical conductors away from the plug sockets. I will take care not to hurt myself or anybody else with the crocodile clips. I will also not turn the power socket on full so as that the wire does not burn or set fire to any surrounding objects or burn anybody. Preliminary work Firstly I assembled the apparatus as shown in the diagram below. For the wire I used 34 standard wire gauge wire. I then took measurements placed the two wire ends marked with an X...
Voltmeter reading by the Ammeter reading, giving me the resistance. This experiment would then be repeated three times so as to determine any anomalous results.

Diagram of apparatus for alternative experiment

I predict that the readings on the Voltmeter and Ammeter would be higher but when divided and the resistance worked out that the resistance would be very similar to that of the results worked out in my main experiment. This would be a useful experiment to carry out alongside my other to support my theory and satisfy my aim.

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The following shows the collision theory...The following shows the collision theory used to explain the effect of temperature and concentration Prediction: In this investigation I expect to find as I increase the temperature the reaction will take place faster. This is because as the temperature increases, it gives more energy to the sodium thiosulphate and hydrochloric acid particles causing them to collide more often and with more force; this increases the rate of reaction. As the temperature rises, a greater number of sodium thiosulphate and hydrochloric acid particles have energy greater than the activation energy therefore leading to more successful collision, and increasing the rate of reaction. * Plan: I will be mixing the two clear liquids 'Hydrochloric Acid' 1M "“HCl and 'Sodium Thiosulphate Solution' 40G/L - Na2S2O3, in order to observe and analyse the reaction changes if any when I increase the temperature. I will add 50cm of weak sodium thiosulphate and 5cm of hydrochloric acid into the beaker; I will make a quick mix of the solution before beginning to start the clock. I will watch the reaction and try to find out whether the solution goes milky and the cross disappears, this will indicate whether the reaction is done. Once the cross has disappeared in the solution I will stop the clock and record the results. Place Apparatus in middle of desk: Boiling tube, test tube, 600ml beaker, kettle, Distilled water bottle, Sodium Thiosulphate, Hydrochloric Acid, Stop Clock, Paper Cross, 25ml measuring cylinder, 100ml measuring cylinder and 10ml measuring cylinder. I will then draw a cross of any size on a piece of A4 paper Prepare Batch of sodium thiosulphate and distilled water using both a 100ml and 25ml measuring cylinders. Place 10cm of Hydrochloric acid into test tube using 10ml-measuring cylinder. Place 50cm of sodium thiosulphate/distilled water solution into boiling tube using a 25ml-measuring cylinder. Put water in kettle and switch on Place a cross on the outside of the 600ml beaker Place 150ml of cold water into 600ml beaker Mix the hot and cold water in beaker Use Thermometer to take the temperature of the sodium thiosulphate and distilled water and Hydrochloric acid with two thermometers in each test tube Wait for the temperature of both the Solution and Hydrochloric Acid to reach the required temperature Pour Hydrochloric acid into solution and start stop clock immediately Wait until cross disappears because of the cloudy solution, and then stop the stop clock Record the time in table Take the temperature of the mixture and record in table Pour away as soon as possible Wash boiling tube out with cold tap water then rinse with distilled water Take average of the start and finishing temperatures and times Repeat Experiments twice for each temperature to improve reliability or to make them reliable. Plot on graph The temperatures that I will carry out the experiments at 25, 30, 35, 40, 45°c. Fair test: I will be able to make this a fair test by keeping all of the solution the same amounts 50cm of weak sodium thiosulphate and 5cm of dilute hydrochloric acid. I will keep these variables the same: Concentration of 2HCl: Concentration of sodium thiosulphate and Hydrochloric acid "“ The concentration of sodium thiosulphate and hydrochloric acid will be kept the same, as to make it a fair test, because if you change the concentration of one reactant it changes the number of particles making the reaction unfair and not reliable. If you create batches of the reactants you reduce the percentage error of volume measurement and of the concentration. E.g. when you measure 25ml of water from a 25ml measuring cylinder a certain amount of water will stay in the cylinder, Then instead of water it was hydrochloric acid and some was left behind, it would change the total concentration because the number of particles has been reduced therefore there is less particles for the other reactant to collide with, also the chance of the amount left behind being the same will be small Volume of Na2S2O3: If I don't keep this constant then it'll effect the reation. Volume of 2HCl: if I don't keep this constant then it'll effect the reation. Temeperature of solution: If I don't keep this constant then it'll increase the energy of the particlesand also increase the chance of a successful collision. I will use the same cross for the whole experiment, also time it accurately and make sure my equipment is working. Equipment: Diagram *Sodium thiosulphate Hydrochloric acid Distilled water 2 Beakers Cross of A4 paper Burette Stopwatch Goggles Funnel Thermometer Water bath To follow this reaction you can measure how long it takes for a certain amount of sulphur to form. You do this by observing the reaction down through a conical flask, viewing a black cross on white paper see diagram below. The X is eventually obscured by the sulphur precipitate and the time noted. By using the same flask and paper X you can obtain a relative measure of the speed of the reaction in forming the same amount of sulphur. Mixè *èOngoing*èWatch stopped* Here is the preliminary result: * Safety: I will make the experiment safe by wearing goggles while handling the irritants and when the reactions are occurring during the experiment. Sulphur and sulphur dioxide are given off during the reactions and are irritants, if breathed in it is dangerous. To avoid this occurring I will keep the room well ventilated by opening windows so the gas can disappear. Each try I do I wash out the beaker several times before starting the experiment. I will make sure the hydrochloric acid does not get in contact with my hands. Analysis: The experiment shows, that when the hydrochloric acid is added to the sodium thiosulphate, a cloudy precipitate appeared. It also shows that when you increase the temperature at which a reaction is taking place, the particles move more quickly resulting in a faster reaction. This has two effects: 1 More collisions take place 2 When a collision occurs, there is more chance that the collision will lead to a reaction, because the amount of energy is more likely to be greater than the minimum amount of energy needed the activation energy Raising the temperature makes the particles move faster. This means that the particles collide more frequently with each other and the rate of the reaction increases. Also, the faster the particles are travelling, the greater is the proportion of them which will have the required activation energy for the reaction to occur. Refer back to prediction diagram HCl+sodium thiosulphatesodium chloride+sulphur dioxide+sulphur+water. HClaq + Na2S2O3aq NaClaq + SO2g + Ss + H2Ol Evaluation: I believe that my results, in general, were very much accurate as I repeated my experiment twice to be able to get an average time taken for the reaction to take place. Providentially, I had no anomalous results which proved the precision and accuracy of my experiment. The method did show the relationship between the temperature and the rate of the reaction. The line graph proves my hypothesis to be correct, but also provides me with some additional information. I have marked on the exact points of the average rate of reaction for every 5 ºC, you can see that at temp 30ºC the speed of reaction did not fall on the line of best fit. This was because the temperature was increased from the previous temp of 25ºC. At 25ºC, the particles would be moving quickly, but not as quickly as they are 30ºC, because as the temperature is increased the particles started moving more quickly and more frequently colliding with more energy so that a faster reaction occurred. Drawing in a line of best fit onto my graph, made it easier to get a more accurate picture from the results. My line graph showed positive correlation meaning that as the temperature was increased the rate of reaction increases. It's also a curve, levelling off gradually. For my Experiment, by having a 5°c rise in temperature allows the number of particles that have energy greater than the Ea Activation Energy 5.45times larger than the number before. This tells me that for this reaction the rate of reaction is almost double for a 5°c rise, therefore shows that the variables were controlled to a sufficient degree of accuracy to allow the reaction to take place at an optimum rate. The experiment was fair and reliable. However, to collect results that are far more accurate, I could have used a mechanical stirrer to act as a catalyst for speeding up the rate of reaction. This would become more precise and dependable. Another factor that we could have improved is the repetitions of experiments; I could have completed the test a further one more time to give me a more adequate average of my results. It was difficult to be able to get both the substances to the required temperature at the same time due to many human errors that can occur. Overall, from my investigation, I believe that the data provides sufficient evidence to support my collision theory as when I increased the temperature the rate of reaction increased. This has turned out to be a successful experiment.   

The following shows the collision theory used to explain the effect of temperature and concentration Prediction: In this investigation I expect to find as I increase the temperature the reaction will take place faster. This is because as the temperature increases, it gives more energy to the sodium thiosulphate and...

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For many centuries, scientists have been...For many centuries, scientists have been puzzling over the question "What is everything made of?". There have been numerous theories and hypotheses drawn up over the millennia, but only one can be correct. This is atomic theory "“ that everything is composed of atoms, which is the smallest any one element can be and cannot be broken up any smaller. Of course, no one person has ever just clicked his or her fingers and exclaimed Archimedes-fashion "Eureka!" and settled the score forever, but the theory today has been based upon the work of many great scientists over time. In this essay I shall look at just a drop in the ocean as far as these are concerned, on the subject of changing atomic models. John Dalton 1766-1844 developed the first useful atomic theory of matter around 1803, developing a hypothesis that the sizes of the particles making up different gases must be different. He came up with the four following points: "¢ All matter consists of tiny particles "¢ Atoms are indestructible and unchangeable - atoms of an element cannot be created, destroyed, broken into smaller parts or transformed into atoms of another element. Dalton based this hypothesis on the law of conservation of mass and on centuries of experimental evidence. "¢ Elements are characterized by the mass of their atoms. All atoms of the same element have identical weights, Dalton asserted. Atoms of different elements have different weights. With the discovery of isotopes, however, the statement was amended to read, "Elements are characterized by their atomic number". "¢ When elements react, their atoms combine in simple, whole number ratios. This suggested a practical strategy for determining relative atomic weights from elemental percentages in compounds. Experimental atomic weights could then be used to explain the fixed mass percentages of elements in all compounds of those elements! Some of the details of Dalton"s original atomic theory are now known to be incorrect. But the core concepts of the theory that chemical reactions can be explained by the union and separation of atoms, and that these atoms have characteristic properties are foundations of modern physical science. One classic diffraction experiment, which examined diffraction of alpha particles helium nuclei containing two positive charges by a thin foil made of gold metal, was conducted in 1911 by Hans Geiger and Ernest Marsden at the suggestion of Ernest Rutherford. Geiger and Marsden expected to find that most of the alpha particles travel straight through the foil with little deviation, with the remainder being deviated by a percent or two. This thinking was based on the theory that positive and negative charges were spread evenly within the atom and that only weak electric forces would be exerted on the alpha particles that were passing through the thin foil at high energy. What they found, to great surprise, was that while most of the alpha particles passed straight through the foil, a small percentage of them were deflected at very large angles and some were even backscattered. Because alpha particles have about 8000 times the mass of an electron and impacted the foil at very high velocities, it was clear that very strong forces were necessary to deflect and backscatter these particles. Rutherford explained this phenomenon with a revitalized model of the atom in which most of the mass was concentrated into a compact nucleus holding all of the positive charge, with electrons occupying the bulk of the atom"s space and orbiting the nucleus at a distance. With the atom being composed largely of empty space, it was then very easy to construct a scenario where most of the alpha particles passed through the foil, and only the ones that encountered a direct collision with a gold nucleus were deflected or scattered backwards. Of course, these are just two of the many findings in this field of scientific research, but what they have helped prove is the basis on all elements and their atoms "“ only now can scientists predict and understand reactions to such a level of accuracy.   

For many centuries, scientists have been puzzling over the question "What is everything made of?". There have been numerous theories and hypotheses drawn up over the millennia, but only one can be correct. This is atomic theory – that everything is composed of atoms, which is the smallest any one...

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Physics Investigation Of Resistance Aim:...Physics Investigation Of Resistance Aim: to investigate how the electrical resistance of a wire changes in relationship to it´s length. Prediction: I think that as the length of the wire increases so to will the resistance of it. I also believe that the rate at which the resistance of the wire increases will be directly proportional to the length. The graph to show this should therefore look something like this: Reason: with electricity, the property that transforms electrical energy into heat energy, in opposing electrical current, is resistance. A property of the atoms of all conductors is that they have free electrons in the outer shell of their structure. All metals are conductors and have an arrangement in similar form to this: As a result of the structure of all conductive atoms, the outer electrons are able to move about freely even in a solid. When there is a potential difference across a conductive material all of the free electrons arrange themselves in lines moving in the same direction. This forms an electrical current. Resistance is encountered when the charged particles that make up the current collide with other fixed particles in the material. As the resistance of a material increases so to must the force required to drive the same amount of current. In fact resistance, in ohmsR is equal to the electromotive force or potential difference, in volts V divided by the current, in amperes I "“ Ohm´s law. As the length of the wire is increased the number of collisions the current carrying charged particles make with fixed particles also increases and therefore the value for the resistance of the wire becomes higher. Resistance, in ohms R is also equal to the resistivity of the wire, in ohm-meters ñ multiplied by the length, in meters l divided by the cross sectional area, in square meters A. The material and cross sectional area of the wire is constant throughout the experiment. Therefore it is clear from the formula that the resistance should be directly proportional to the lengthKey factors: in this experiment we will only change one factor, the length of the wire. This should effect the resistance of the wire in the ways stated above. Fair test: in this experiment we are only changing one factor "“ the length of the wire, the factors that we are going to keep the same are as follows: We must keep the surrounding room temperature the same or the particles in the wire will move faster if the temperature is increased and this will therefore have an effect on the resistance. The cross sectional area of the wire must be kept constant throughout as well. This is shown in equation 2 where the cross sectional area is a factor that effects the resistance. The material of the wire must also be kept the same as different materials have different conductivity. The last two factors will be kept the same by using the same wire all of the way through the experiment. The current that we pass through the wire is to be kept the same, also. If this is changed the temperature of the wire might change in a way that is not constant making the results more confusing. Apparatus: 1. Wire, over 50 cm long 2. Rheostat 3. Power supply 4. Six connecting wires 5. Two crocodile clips 6. Voltmeter 7. Ammeter Plan: 1. Connect circuit as shown in the diagram. 2. Adjust rheostat until the ammeter reads .3 A. 3. Record voltage on voltmeter 4. Repeat the experiment with the following lengths of wire, connected between the two crocodile clips: - 10 cm - 15 cm - 20 cm - 25 cm - 30 cm - 35 cm - 40 cm - 45 cm - 50 cm 5. Use Ohm´s law to find the resistance of the wire, equation 1. Diagram: Safety: this is not a very dangerous experiment but despite this you must always handle electricity with care, keep the current low, handle with dry hands etc. Accuracy: to keep this experiment as accurate as possible we need to make sure, firstly, that the length of the wire is measured precisely from the inside edge of the crocodile clips, making sure that the wire is straight when we do this. We must also make sure that the wire is straight when we conduct the experiment. If it is not, short circuits may occur and bends and kinks in the wire may effect the resistance, also. The reading that we take of the voltage should be done fairly promptly after the circuit is connected. This is because as soon as a current is put through the wire it will get hotter and we want to test it when heat is effecting it the least, i.e. at the beginning Preliminary: upon testing to see if the experiment would work I found no problems with the plan I described earlier. I was able to get the following results: LENGTH cm CURRENT A VOLTAGE V RESISTANCE =V/IÙ 10 0.3 0.13 0.43 15 0.3 0.20 0.66 20 0.3 0.27 0.90 25 0.3 0.35 1.16 30 0.3 0.42 1.40 35 0.3 0.48 1.60 40 0.3 0.57 1.90 45 0.3 0.60 2.00 50 0.3 0.68 2.26 Observations Observations: we will observe the reading on the voltmeter change as we change the current to .3 A. we also observe a general increase in the voltage as the length of wire we use gets longer. The rheostat will also be set at different positions for the different lengths of wire that we use. Evidence: to make sure our overall values are as accurate as possible we will repeat our readings 3 times and then take the mean resistance of the 3 readings. We will also be able to spot and discard any anomalies from our results. Results: Set i Length cm Current A Voltage V Resistance =V/I in Ù 10 0.3 0.13 0.43 15 0.3 0.20 0.66 20 0.3 0.27 0.90 25 0.3 0.35 1.16 30 0.3 0.41 1.36 35 0.3 0.48 1.60 40 0.3 0.56 1.86 45 0.3 0.62 2.06 50 0.3 0.69 2.30 Set ii Length cm Current A Voltage V Resistance =V/I in Ù 10 0.3 0.13 0.43 15 0.3 0.20 0.66 20 0.3 0.27 0.90 25 0.3 0.35 1.16 30 0.3 0.42 1.40 35 0.3 0.49 1.63 40 0.3 0.57 1.90 45 0.3 0.61 2.03 50 0.3 0.70 2.33 Set iii Length cm Current A Voltage V Resistance =V/I in Ù 10 0.3 0.13 0.43 15 0.3 0.20 0.66 20 0.3 0.28 0.93 25 0.3 0.34 1.13 30 0.3 0.40 1.33 35 0.3 0.48 1.60 40 0.3 0.57 1.90 45 0.3 0.62 2.06 50 0.3 0.70 2.33 Average Length cm Resistance Ù-Set i Resistance Ù-Set ii Resistance Ù-Set iii Mean Resistance Ù 10 0.43 0.43 0.43 0.43 15 0.66 0.66 0.66 0.66 20 0.90 0.90 0.93 0.91 25 1.16 1.16 1.13 1.15 30 1.36 1.40 1.33 1.38 35 1.60 1.63 1.60 1.61 from 40 1.86 1.90 1.90 1.89 45 2.06 2.03 2.06 2.05 50 2.30 2.33 2.33 2.32 Anomalies: there was only one real anomaly in this experiment and it has been highlighted like this: 000 Analysis Trends: from the graph we can see one very clear trend, which is, as the length of the wire increases so does the resistance of it. Another, more significant thing is that it the increase is constant. This is indicating by the fact that the line drawn is a straight one. One may also note that the gradient of the line drawn is 1.85/40 .04625. Conclusion: I think that from my results I can safely say that my prediction was right. The resistance did change in proportion to the length. This is because as the length of the wire increased the electrons that made up the current, had to travel through more of the fixed particles in the wire causing more collisions and therefore a higher resistance. We can work out what the resistivity of the wire should be from our results using the It is obvious from the formula that R/l is simply the gradient of the graph, therefore Evaluation I feel that overall our results were quite accurate. This is can be seen when we look at the graph, which shows a straight line with all of the points apart from one being very close to or on that line. The one point that was not that close to the line was a slight anomaly, but it was only slight and did not effect the final gradient of the graph. I have found out that for the wire I was using, the resistivity at 20©C is 4.9 X 10-7 ohm-meter. From this we can then work out the percentage error of our results: The accuracy for this experiment is, theoretically, ± 15.7%, but as one can see this does not seem to be the case from looking at the graph. The reason for this could have been due to a number of different factors. Firstly the temperature of the wire was not necessarily 20©C when we conducted the experiment and the material of wire may not be as pure as it should have been. The main reason for this was probably due to the equipment that we used being inaccurate. This did not stop us from seeing the trend, though, because the equipment would have been out by a constant amount each time therefore there was a constant error. So the trends that were predicted in the plan still were shown. Most errors in our experiment were encountered in the measuring of the wire. This is because it simply was not very practical to hold a piece of wire straight, whilst holding it next to a ruler and then trying to accurately fix crocodile clips to the right part on the wire. Also I do not feel that the crocodile clips were always fixed securely to the wire with a good connection. This also meant that they were easy to move about on the wire changing the length of it. Errors rarely occurred in the setting of the current and the reading of the voltage. It was just in the preparation area that they did occur. Another example of this is the wire was never totally straight when we started the experiment, which may also, as said earlier on, effect the resistance of it I do not think that doing any more results in our experiment would have made it any more accurate. I feel that the only way to make it more accurate would be to use a different method "“ perhaps were we had a bar that did not bend in place of the wire. We could even use a rheostat in place of the wire, because it is essentially a long coiled wire that is connected at different lengths to change the resistance of the circuit   

Physics Investigation Of Resistance Aim: to investigate how the electrical resistance of a wire changes in relationship to it´s length. Prediction: I think that as the length of the wire increases so to will the resistance of it. I also believe that the rate at which the resistance...

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