In this investigation, I will be looking at the resistance of a solution, and the different things which affect it. In this experiment, I have chosen one variable, the salt concentration.
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Investigating the resistance of a solution In this investigation, I will be looking at the resistance of a solution, and the different things which affect it. In this experiment, I have chosen one variable, the salt concentration. I have chosen the following variables for the concentration: in a beaker of 50ml (cm ) : 0 grams, 1,2,3,4 and 5 grams. Using the circuit shown below, I will find out the resistance of the salt solution. I will keep the following variables the same: I will keep the temperature at room temperature, by not changing the room temperature at all, by keeping windows shut, and not adjusting the radiators during the experiment. I will monitor the temperature, and make a note, just incase it changes. I will monitor the temperature using a thermometer, which will be placed into the beaker during each experiment. I will keep the voltage at 5V and 50cm of solution, to keep it a fair test. The circuit will include a power pack, an ammeter, a voltmeter, two iron rods, a beaker, wires with crocodile clips and a measuring tube. I will repeat each experient once, so that I can find out an average, which will prevent anomolies affecting the graph, and incase there is a difference between the first attempt, and the second attempt, I will be able to spot the mistakes. Method To begin with, I will place the two rods in the beaker with wires connected as shown: The ammeter is connected in series, and the voltage is measured in parallel.
Preliminary work Before carrying out the final experiment, I tried a test experiment, to see how the experiment would work. I received the following results after setting up the circuit as explained above: Grams of salt per 50cm Voltage Current Input Voltage Resistance 0 3.86 0.00 5 386.00 3 4.15 0.41 5 10.12 5 4.10 0.58 5 7.06 This preliminary experiment showed me that I might have to use a higher voltage, because there would be a wider range of voltage readings, and this would make a graph more easy to read and understand. I believe that 7V would be a better input voltage to have, because it is not too high, and it is not to small, as it is a higher voltage used in my preliminary work. It shows me that 50cm is enough water to use, because it will dissolve the amount of acid I plan to use, 5g of salt. It is important that it can dissolve into the solution, because when it comes to the point when no more salt can be dissolved into the solution, it affects the results, because adding more salt has no effect on the reisistance anymore. Apparatus Apparatus Use for apparatus Power pack To supply the power Wires To connect the circuit Voltmeter To measure the voltage Ammeter To measure the current Beacker To hold the salt solution Rods connected to block To keep the probes at equal distances Crocodile clips To connect the rods to the circuit Measuring cylinder To measure the water amount Distilled water To make salt solution Results Salt/g Voltage supply Water/ cm Current (A)
I could vary the temperature of the experiment, my heating the beaker before carrying out the experiment, and monitoring the temperature throughout. I would set up the circuit, as shown in my plan. Before putting the solution in a beaker, into the circuit, and placing the rods into the solution, I will heat the beaker on a tripod over a bunsen, with a thermometer in the beaker. When the temperature inside the beaker has reached the required temperature for the experiment, I will remove it from the tripod, connect the circuit, and record results. I will then rince out the beaker, and repeat the experiment again to a different temperature each time, with different temperatures. This would show whether temperature affects the rate or not, because in my experiment, the temperature remained constant. I could use different waters for my experiment. I used distilled water, as to not affect the results. If I was to use tapwater, I could monitor whether the particles within the tapwater affected the results or not, and whether they conduct electricity, and decrease the resistance. I believe that the experiment would be improved, if different solutions were formed, for example, using a different material to salt, to see if this would produce the same results in terms of results. I used a D.C supply, this was because I wanted to keep the particles at the same charge throughout the experiment, I could improve the experiment, by using an A.C current, to see if this affected the resistance. I could use a larger amount of water,because this would enable me to dissolve more salt into the solution, and therefore give a wider spread of results.
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