Before carrying out the actual experiment I improved my method by altering the problems found during the trial.
Temperature
Again make sure that all concentrations of solutions used in the experiment are uncontaminated since this would immediately make the results of the experiment invalid. Then set up the apparatus as shown on diagram 2. Then measure 50 ml of sodium chloride into the beaker. Place the digital thermometer into the solution then Heat the solution using the Bunsen burner. Remove the heat and place the electrodes into the solution. Afterwards switch the power pack on and take the readings of the ammeter and voltmeter. Then heat the solution for till the solution reach the next desired temperature and carry out the same process. Repeat the experiments for all the temperatures. Carry out the same experiment again but this time change the electrode and use copper electrode.
Replicate the experiment again but this time with sulphuric acid. Making sure all the process is repeated.
Modifications to experimental method following trial.
In my I found that it was very hard to heat the solution to a certain temperature because during heating the temperature rise was very rapid and did not allow enough time to take accurate readings.
Improvement- Instead of heating the solution to one temperature after the other, I found that by heating the solution to the maximum temperature and leaving it cool to the necessary temperature was more effective.
The maximum temperature I went up to was 83 °c because my preliminary work showed that solution started to boil above this temperature, so I knew if that happened my experiment would not have been fair.
Before carrying out the actual experiment I improved my method by altering the problems found during the trial.
In my final experiment I only tested one concentration of both solutions because all concentrations should show the same effect in conducting the current when the temperature is increased.
Apparatus List
Voltmeter - Clamps & Clamp stands
Ammeter - Bunsen burner
Digital thermometer - Crocodile clips
50 ml beakers
Graphite & Copper electrodes
Power Pack
Connection leads
Setting of the apparatus
Diagram 1 (Concentration)
Diagram 2 (Temperature)
Hypothesis: What effect does different concentrations of the solution (0.5M, 1M, 1.5M, 2M, 2.5M & 3M) have on the conductance of a solution?
I hypothesise that as I concentration of the solution is increased the conductance of the solution will also increase. I predict the rate of the conductance is directly proportional to the concentration. This is because in solutions, the process of electrolysis conducts electricity, which is when the compound dissociates into its constituent ions. These ions then carry the charge from one electrode to the other. So going back to concentration we can see if the concentration is increased there will be more ions and charge carriers present in the solutions, causing an increase in the conductance.
I hypothesise when I plot a graph for concentration against conductance I will expect to get a similar graph to the one below:
I predict the graph will have the following shape because when the concentration increases the conductunce is also incraesing at the same time.
Hypothesis: What effect does different temperatures of the solution (ranging between 20°C to 90°C) have on the conductance of a solution?
I hypothesise as I increase the temperature of the solution the conductance of the solution will also increase. This happens because when we heat the solutions, the in the ions in the solution get a bigger kinetic energy from the heat. The extra kinetic energy makes the ions move vibrate faster. This leads to rush in the electricity transfer between ions to ions and it leads to the increase in conductance.
I hypothesise when I plot a graph for concentration against conductance I will expect to get a similar graph to the one below:
I predict the graph will have the following shape because when the concentration increases the conductunce is also incraesing at the same time.
Hypothesis: What effect does different solutions (Sodium Chloride& Sulphuric Acid) have on the conductance rate of a solution?
I hypothesise out of the two solutions Sulphuric acid will conduct the solution better than sodium chloride. I think this will happen because in sulphuric acid there are more positively charged ions to carry the electric charge than there is sodium chloride. In sulphuric acid there are 2H+ ions where there is only one Na+. So more positively charged ions the better the conductance will be.
Hypothesis: What effect does different electrodes (Carbon & Copper) have on the conductance rate of a solution?
I hypothesise Carbon will have better conductance rate than some Copper because it’s a better conductor of electricity than copper. So better conductor means the higher conductance.
Results
Concentration
Sodium Chloride (Carbon electrode)
Sulphuric acid (Carbon electrode)
Sodium Chloride (Copper electrode)
Sulphuric acid (Copper electrode)
Temperature
1 M Sodium Chloride (Carbon electrode)
1 M Sulphuric acid (Carbon electrode)
1 M Sodium Chloride (Copper electrode)
1 M Sulphuric Acid (Copper electrode)
The results above were averaged out and in some cases they are rounded up to certain degree of accuracy.
I used the following formula to calculate the results:
If: G=1/R and R=V/I
Therefore: G= 1 _ ⇒ G = I / V
(V/I)
Working out Error bars and Error box
When we take the reading of any apparatus such as voltmeter, ammeter or thermometer there is always going to be an error. This error will have an effect on the graph we plot so we also need to plot the error points on the graph in order to find the actual line. If we were plotting error points for any other experiments, we will only have to plot ± a certain value. But in this certain case we have to work out the Gmax and Gmin to plot in the graph because conductance is worked out from two points. Also due to the restrictions in Microsoft excel we have to work the average of these max and min results and subtract them away from the actual reading to find the Errormax and Error min.
Absolute errors:
Voltage (v)- 0.05 volts current (i)-0.0005amps temperature- (t) 0.05
G=I / V
Gmax = I max = I + ΔI E max = I + ΔI - I / V
V min V-Δv V-Δv
When I = 0.311 V= 1.9 G=0.164
E.g. -: Gmax = 0.3115 = 0.168 (3.d.p)
1.85
finally E max = 0.168 –0.164= 0.004
Also Gmin = Imin = I - Δi
Vmax V+Δv
Gmin = 0.3105 = 0.159 (3.d.p)
1.95
finally E min = 0.159 – 0.164 = - 0.005
Sodium Chloride (Carbon electrode)
Sulphuric acid (Carbon electrode)
Sodium Chloride (Copper electrode)
Sulphuric acid (Copper electrode)
Temperature
For the temperature the error is going to be constant ±0.05. However for we have to work out the Emin and Emax. .
1 M Sodium Chloride (Carbon electrode)
1 M Sulphuric acid (Carbon electrode)
1 M Sodium Chloride (Copper electrode)
1 M Sulphuric Acid (Copper electrode)
Analysis
What effect does different concentrations of the solution (0.5M, 1M, 1.5M, 2M, 2.5M & 3M) have on the conductance of a solution?
Graphs 1 – 4 illustrate the relationship between of conductance against different concentration. All four graphs are upwards sloping curves, which all show that as the concentration increases; the value of conductance increases in magnitude illustrating a direct relationship.
Graphs 5-8 illustrate the relationship between of conductance against different temperatures. Again all four graphs are upwards sloping curves, which all show that as the concentration increases; the value of conductance increases in magnitude illustrating a direct relationship.
Graph One (Sodium Chloride (Carbon electrode))
From this graph I can see that as the concentration of the sodium chloride increases by every 0.5M the conductance also increases by a by a value. In between 0-1 M the line of best fit is almost a straight line. From 1-3M the line steadily slopes up wards.
Graph Two (Sodium Chloride (Copper electrode))
The graph shows a steady increase. The slope is constantly increasing all the way and most of the points fell into the line of bet fit.
Graph Three (Sulphuric acid (Carbon electrode))
This graph is very similar to the first one. At the start the gradient is almost constant and it’s almost a straight line. The from about 1M the slopes upwards and increases the gradient.
Graph Four (Sulphuric acid (Copper electrode))
Unlike the other graph this graph has a different line. Unlike the other slopes this one increases straight from the start. It has steeper gradient, which shows that it has a faster rate.
Temperatures
Graph Five (1 M Sodium Chloride (Carbon electrode))
This graph again has a similar slope. As the temperature increases the conductance is also increasing. In the graph until about 40°C we get a straight line with a very straight gradient. After that the line increases monotonically with an upward slope. I think the reason we get a curve like this is because the conductance readings are very close together.
Graph Six, Seven and eight
The shape of curves these graphs are similar. As the concentration increases the conductance also increases. They are all increasing at a steady rate. They also have an upward slope.
Conclusion:
What effect does different concentrations of the solution (0.5M, 1M, 1.5M, 2M, 2.5M & 3M) have on the conductance of a solution?
°°
We started this coursework towards the start of July. I spent the first week doing research and gathering information that could help me with my coursework. I used the next few I lessons to write up my plan and decide what apparatus will needed. After that I spent the next week carrying out a trial experiment for all the variables concerned. It took me between 6-7 lessons. I spent the following two lessons to input my modifications and to alter my plan.
Once everything was finalised I spent the about 6-10 lessons carrying out the actual experiment. Finally I spent the rest of the time writing up the results.