Whilst you are trying to push through all that GCSE content for your science exams, there is something that you need to remember to do first, and that is learn how to use your calculator.
Standard form: this is the most important button that you need for science. Standard form is used for writing large or small numbers without having to write lots of 0s. You can read more about it on this link as this article is about how to get it on your calculator. To write standard form, you write the number (which should only have one number before the decimal place). Then you need to fin the EXP or the 10x button (the x is superscript). It is on the bottom of the calculator. You then type the number that the power of 10 should be. If it is a small number, you press the (-) key first.
Do NOT write 10 then x then the number as this may give different results as you are actually multiplying the number by 10x and this may invoke BIDMAS.
You can convert a large number to standard form with the ENG button. This moves the decimal place in one direction. To move it in the opposite direction, press the SHIFT + ENG button.