AQA GCSE Chemistry C2/C3 May 15th 2014

Thats correct but the explanation is weak, the ink from the pen would have dissolved in the solvent, rising up the paper, therefore messing up the experiment.

Hey where are these rumoured?

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I liked these papers generally. Only questions I didn't get were:
- the titration calculation for C3.
- the final question on the Haber process in C3. Guessed it was by fractional distillation even though that's alkanes from C1.
- the question about why silver is in water filters, again guessed because it kills microbes.

I think the two methods of water treatment for the first question were filtration to remove any solid particles, and treatment with chlorine to kill any microbes that may be in the water.

I think those are about right

Hey, when are the official boundaries released?

what did you guys get for the titration calculation in C3? I got 0.17 and this makes sense because:

The other substance had a volume of 25cm3 with a conc. of 0.2mol/dm3. The concentration of the substance looked for must have been less as this substance had a higher volume (26.8cm3)?

I got this as well, we got the volumes the wrong way round (they sneakily put them in a weird order )

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really?
http://www.telegraph.co.uk/education/educationnews/10255180/Schools-moving-to-easy-IGCSE-exams-to-boost-grades.html

http://news.tes.co.uk/b/news/2013/08/20/schools-think-igcses-are-quot-way-easier-quot.aspx

is it me or you just contradicted yourself there lol

hey, you know on c2, what did people put for a) silica question about lower melting point,
b)how nanotubes are used as lubricants?
c)the question about conclusion of nanometeres on ph graph?
cheers guys

a) Silicon Dioxide is mixed with other substances to make glass. I presumed the other substances simply cause the melting temperature to decrease (in comparison to Silicon Dioxide).

b) I think the layers of atoms can maybe slide over each other which is similar to graphite, and as they are nano-sized they have a very large surface area (I don't know how it relates to lubricants but I think that's what they're looking for).

c) The smaller the size of the particles, the greater the percentage of bacteria killed, and Bacteria Type 2 are slightly more resistant to the nano particles than Bacteria Type 1.

I don't know for sure if these are right but that's what I put from what I can remember

a) I said it may increase the transparency of the glass as it stated in the question that the product already has a low melting temperature

b) Yeah, the atoms can slide over each other which means that it is slippery or there will be less friction between it and other surfaces

c) Wasn't it the bigger the size of particles?

It was definitely smaller, I can still picture the graph

so can I

Well it's commonly taught in Chemistry that increased surface areas increase the rates of reactions so it is fairly obvious to assume the smaller the nano particle, the more effective it was at killing bacteria