[Eneri]

Hi guys  um if this helps to determine my level,  i'm in tenth grade in MYP system.
 And this is about a lab assignment in which we have set up a factor to investigate how that factor affects the voltage produced in an electrochemical cell (a copper-zinc Daniell cell).

I chose my independent variable as concentration of electrolytes (in Molecule).

I wrote this for my hypothesis:

As the concentration increases, the voltage will increase. Therefore, the correlation between the voltage produced and concentration of electrolytes would be positive, although not strong. This accounts for the estimation that more molecules in the electrolyte solution would produce more electrons, consuming ions from the oxidized electrode’s electrolyte and plating the reduced ions from the reduced electrode’s electrolyte onto the other electrode.
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I'm not confident about what I wrote. Is the reason mainly on conductivity or something? I'll admit the hypothesis sounds kinda unclear.

Also I carried out the experiment today, using different electrolytes of the same concentration each time (e.g. 0.25M, 0.5M, 1M), but the voltage didn't vary as much, not fitting my hypothesis. And I've no idea...

  Please, wise scientists or anybody else who could clarify this for me.. I'll be grateful for your help.

[Borek]

Please elaborate - what is your cell, what are concentrations of all ions present, which ion concentration do you change.

There are several effects that will change the voltage, your description is not precise enough.

[Eneri]

Please elaborate - what is your cell, what are concentrations of all ions present, which ion concentration do you change.

There are several effects that will change the voltage, your description is not precise enough.

it's a Daniell cell with electrodes of copper and zinc and electrolytes of copper and zinc sulphate, and its salt bridge is potassium chloride. I'm varying the concentration of both electrolytes

and these are a list of controlled variables:
Controlled
-   Mass of electrode
-   Volume of electrolyte (100 ml)/ Depth of electrodes in electrolytes (1.5cm)
-   Type of metals used for electrode (Copper and Zinc)
-   Length of wires
-   Length of electrodes (12cm)
-   Length of salt bridge (18.5cm)
-   Salt bridge solution (0.5M)

[Borek]

it's a Daniell cell with electrodes of copper and zinc and electrolytes of copper and zinc sulphate, and its salt bridge is potassium chloride. I'm varying the concentration of both electrolytes

Change concentration of only one metal solution (for example copper only), and change it by much - say 100 times (use 0.01M solution and 1M solutions), or even 1000 times (0.001M/1M).

How accurate are your measurements of the voltage? You need to be able to measure reliably several millivolts.

[DevaDevil]

you are increasing the molarity (activity) of one of the reactants in the cell: see Nernst equation