Unit 3 is practically based on units 1,2 .
if you use your edexcel AS active book, while studying your units 1 and 2 you will find practical work box in each chapter. this can be used for your unit 3. so thats how u prepare for unit 3. plus, solve many unit 3 papers. they are similar evry year.i did this for chemistry, i solved many papers and just skipped much of what's written in the book and i got 56/60 , an A. so just practice papers very well and incase u need anything, just PM me.
