Bonds.
divorce
There is no 40-letter word the longest English word ishippopotomonstrosesquippedaliophobia (36 letters)Pneumonoultramicroscopicsilico volcanoconiosis (45 letters) (no Break)Had to put a break in, otherwise the full word would not show.
marathoning
wreck smash break spoil
day
These structures are bonds. 100% positive.
It should be reactants but it is 9 letters word so it must be Substrates.
break, dumbhead
divorce
vestigial
There is no 40-letter word the longest English word ishippopotomonstrosesquippedaliophobia (36 letters)Pneumonoultramicroscopicsilico volcanoconiosis (45 letters) (no Break)Had to put a break in, otherwise the full word would not show.
snap, tear.
Holiday
vacation
marathoning
Reactants participate in a chemical reaction. The word is a noun.
Ribosomes