nichrome wire length prac + thiosulfate ions concentration prac

[Gilly]

Currently doing pracs that our teachers propose we submit to IBO, although they seem really simple to me - we did everything (D,DCP & CE) however the design seemed frigtheningly obvious for both, so just checking whether these topics and my subsequent research questions would be acceptable to submit to the IBO:

PHYSICS
Factors affecting resistance in a wire.
- What affect does length of nichrome wire have on the resistance of this ohmic conductor in a closed circuit?

CHEMISTRY
Factors affecting rate of reaction
- What affect does the concentration of sodium thiosulfate have on the rate of the reaction between aqueous sodium thiosulfate and aqueous hydrochloric acid at room temperature?
(Is this too specific, all I varied was concentration of sodium thiosulfate)

Also, I know that we have to be assessed twice on design, DCP and CE, but could we for the sake of these three criterions be assessed based solely on two pracs - or do we need 12, with each fulilling only one criterion (note: I am completing the exams in November 2009, in case Internal Assessment has changed recently)

[babakren]

I think that's pretty much ok.
but for the chemistry, you need know the variables. So you're varying the concentration which is the independent variable
but what's the dependent? the rate i guess.. so how will u calculate the rate?
Na2S2O3(aq) + 2HCl(aq) --> SO2(g) + S(s) + H2O(l) + 2NaCl(aq)
will it be the volume of SO2(g) per time, mass of S per time, or concentration of NaCl per time?
just get specific with that and itll be ok =]

[Gilly]

I varied the volume of Na2S2O3, but kept total volume the same to ensure depth didn't change. I measured time, and used the inversely proportional relationship between rate and time to find the rate from this. Thanks for your help.