Where to find past papers:
If you want past papers for Edexcel IGCSE this site is better
It has the most recent ones on there.
This is useful for biology questions – more relevant to CIE.
For CIE IGCSE past papers
Where to find simple explanations to help you understand the content:
This is a good site for Chemistry, but I find it too stressful to look at – it’s very ‘busy’!
Also this site for Edexcel chemistry revision resources
Whatever you look at make sure it’s relevant to your specification – there is a fair bit of overlap between CIE and Edexcel but you don’t want to waste your time learning to wrong explanations/ irrelevant content.