beaker
The pressure
I would answer as mechanical as it involves more of physics rather than chemistry.
bladderbloodbonesbrain
The Nobel Prize in Chemistry 1965 was awarded to Robert B. Woodward for his outstanding achievements in the art of organic synthesis.
The Nobel Prize in Chemistry 1993 was awarded for contributions to the developments of methods within DNA-based chemistry jointly with one half to Kary B. Mullis for his invention of the polymerase chain reaction (PCR) method and with one half to Michael Smith for his fundamental contributions to the establishment of oligonucleotide-based, site-directed mutagenesis and its development for protein studies.
BottleBinBasketBag
No U.S. states begin with B.
* bilby * bandicoot
Birr
* beetroot * broccoli
boris
bracken
basil
brine
bratwurst
Burlap Baft
Batman is a super hero. His name begins with b.