If you took your SPA last year (ie. you were in JC2 in
2012), then you do not need to retake SPA. SEAB-Cambridge will use
your results from last year.
If you were in JC more than a year ago (eg. you were busy with
NS in the last 2 years), then your previous SPA results are no
longer valid for use in this year's A levels.
If so, you will have to take a Practical Paper instead of SPA.
For H2 Chemistry, the Practical Paper is on 24 Oct 2013, and
details of your shift (there are usually 2-3 shifts for every
Practial Examination) will be sent to you via SingPost a week
before.