Experiment To Investigate The Resistance Of Brine

Soaked Paper Essay, Research Paper

This

experiment aims to investigate the resistance of brine soaked paper when an

electrical current is passed through it. Planning: ?Previous experiments have taught me that the

electrical resistance will rely on several key variables.? These include the length of paper, its

thickness but most importantly the number of sodium and chlorine ions carrying

the charge.? Knowing this, I have

decided to investigate the concentration of brine in this experiment.? To provide an accurate prediction, I must

research into the scientific details in this experiment and recall information

from previous investigations.? This will

give me a greater understanding of the experiment?s implications and likely

results.Ionic

compounds do not have a molecular structure, but form a three-dimensional array

of ions called a crystal lattice.? In a

crystal of sodium chloride, the ions are arranged so that each Na+ ion is

surrounded by six Cl- ions and

vice versa.? Because the ions are held

rigidly in place by the electrostatic attractions between any one ion and the

oppositely charged ion surrounding it, these compounds tend to be very

brittle.? They do not conduct electricity

when in a solid state, since the ions are not mobile.? However, when in solution or in the molten state, ionic compounds

will conduct electricity by the movement of ions.In this

investigation, two electrodes will be placed on paper soaked in brine and an

electrical current will be applied.? The

sodium chloride is in a solution with water so that the ions are free to

disassociate.? The sodium ions should

migrate to the negative electrode and the chloride ions migrate to the positive

electrode, causing an electrical current to flow.? Having singled

out the most influential factor, and researched into the formation and

qualities of the sodium chloride compound, I have formed a prediction.? I predict that the higher the concentration

of sodium chloride in the brine solution, the lower the resistance.? This prediction is based upon the fact that

at a higher concentration, there will be more sodium chloride ions creating

lower resistance.Method: 1.?????? Connect the circuit,

ensuring that the voltmeter is in parallel with the brine soaked paper.To investigate

the resistance of brine soaked paper; I will set up an electronic circuit. I

will utilise a battery, variable resistor, wire, voltmeter and a milli-ammeter.

I am using a

milli-ammeter because the difference in current is likely to be minute and this

will give me a more accurate reading.? I

am using a variable resistor so that I can take several readings (repeating my

results) to form an accurate investigation. 2.?????? Measure out 10 ml of

solution in six test tubes.The salinity

will be varied by diluting a 1M solution of brine to different ratios of salt

to water. To obtain

accurate readings, the same amount of brine will be used for each result

(10ml).? This will be measured using a

measuring cylinder.? 3.?????? The paper will be placed

in a test tube of brine for the specific time of five seconds ensuring that the

paper is completely coated in brine.?

The paper will only be soaked for a specific time because over a longer

period paper will absorb a greater amount of liquid.? By controlling the time, I can create a fairer experiment.The amount and

type of paper will be identical for each reading.? I will use a 6Ч2 cm rectangular sized piece of paper.? If I used differing sizes of paper then my

results would be inaccurate as more brine could be absorbed or the greater

amount of paper would create a higher resistance.? 4.?????? The brine soaked paper

will be connected into the circuit using crocodile clips.? To prevent contamination or loss of brine,

forceps will be used to transfer the paper from the test tube into the circuit.5.?????? To discover the

resistance of the brine soaked paper; I will record the voltage and current at

each concentration repeating each reading three times and then formulate the

resistance using the formula:Resistance = Voltage ?????????????????? ?? CurrentI will then

take the average of my readings to ensure accurate results and reduce the

effect of any inaccuracies.Obtaining Evidence/Analysing Evidence ?And Drawing Conclusions: I have

tabulated the results of the experiment so that any patterns will become more

apparent and I can distinguish whether my hypothesis was correct.? The concentration column in the table states

the percentage of brine as opposed to water used to test each reading.? 1. Concentration Current Voltage Resistance 2. Concentration Current Voltage Resistance After taking

these readings, I realised that although both tables 1 and 2 show a similar

trend, the actual figures are very different.?

They vary from a resistance of 468 ohms at one reading to 235 ohms at

the same concentration.? Although I had

been careful to keep the same brine for each reading and controlled the other

key variables, the readings had been taken on separate days.? The milli-ammeters I used were different

causing the recorded current to also be different.? I decided to repeat the entire experiment again repeating

readings on the same day (See Table 3).I have

formulated the readings into a graph to help illustrate any patterns in the

data, find the anomalous results caused by mistakes in the investigation and

try to determine the validity of my original prediction (See ?Graph 1?).? The graph

illustrates a very distinct relationship between the concentration of salt and

the resistance of the brine soaked paper.?

It depicts that brine is inversely proportional to resistance. The

greater amount of brine, the lower the resistance.When the paper

was soaked in water only (concentration 0%), there was a very high resistance

yet some current passed.? This may have

happened because tap water was used and it may have contained traces of metal,

which could carry current.? At a concentration

of 20%, the resistance dramatically reduced decreasing from 390 ohms to 48

ohms.? It then steadily reduced as the

concentration increased producing the curve on the graph.These results

appear to prove my original hypothesis ?The higher the concentration of sodium

chloride in the brine solution, the lower the resistance?, as all of my

readings reflect this prediction. However, to be certain of this, I would need

to form a more detailed investigation, correct any anomalous results and create

an even more accurate and fair test. Evaluating: My results

seem reliable as the data produced a graph with a clear line of best fit.? However, discrepancies could have caused

slight inaccuracies in this investigation.?

As I mentioned earlier, I used tap water to dilute the brine to gain

different concentrations.? This meant

that with no salt, some current was able to pass due to the impurities in the

water.?? To create a fairer test, I

should have used distilled water.In this

experiment, I took readings at six different concentrations repeating each

three times.?? If I were to repeat the

entire experiment, I would be sure to record at least ten readings repeating at

each concentration five times.? To

enable readings that are more accurate a more advanced ammeter could be used

because the difference in current is small.?

The readings taken from the ammeter I used, were only for three

significant figures and so inaccuracies occurred.When I

repeated results, the readings were similar however, as I was working with

milli-amps, slight differences increased after the resistance was formulated.By observing

the graph, you can see that in this investigation there were no obvious

anomalies.? As I repeated and averaged

my results, any minor inaccuracies were cancelled out.? I feel that

overall this investigation was accurate and it opens up further possibilities

for future experiments.? These include

investigating whether the thickness of the paper or length of paper would

greatly influence the resistance.