Same pair of letters to be inserted for the answers. I will give hints.
-1. _ _os_ _ate. Chemistry
-2. S_ _safr_ _. Get off your posterior
-3. L_ _or_ _e. Jelly bean
-4. C_ _rth_ _se. Two vowels
-5. _ _mpera_ _. Sounds like something on a golf course.
-6. _ _s_ _cere. This pair of letters form a word themselves
-7. C_ _p_ _al. No clue, too easy.
-8. Par_ _ _ _ on. You may have one of these at work
9. H_ _rtb_ _t. If you are playing this you have one (so many per minutes)
-10. _ _the_ _tics. 2 + 2 = 5