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.

Then, I will connect the circuit, shown below, and turn the power pack on.

| | = two probes in soultion

Then I will take a note of the voltage(P.D) and the current in the circuit, using the voltmeter and the ammeter

I predict that, the more salt there is in the solution, the more current and voltage in the circuit , i.e less resistance. This is because, when there are a larger amount of irons in the solution, i.e. salt particles, the electricity will conduct better, because the electricity can pass through the solution easily, with more particles to travel across within the solution. I predict that the graph made with the results from my experiment will end in a horizontal line, this is because when more salt is added, it will no longer have any more affect on the resistance, because once a certain amount of salt is put into the solution, on adding any more, it will not dissolve, and therefore, the concentration of salt will not have been altered. This will mean that it will have no affect on the resistance, which is affected by the salt concentration.        

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        Another thing which could affect the results, or change the experiment to show the results better, would be to use elements with a charge of 2+ and 2-, so that they will react. I am using two elements with 1+ and 1- in this experiment.

        One thing which could affect the results is heat. When electricity is put through water, it creates heat. During this experiment, there is going to be heat produced. This may, or may not affect the results preceeding the experiment, because the next experiment will be performed in the same solution as the previous one, after ...

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