This disclosure provides systems, apparatuses, and methods for liquid transfer and performing reactions. In one aspect, a system includes a liquid transfer device having a housing having a pipette tip and a plunger assembly; and a reaction chamber, wherein the housing of the liquid transfer device is configured to sealably engage with the reaction chamber. In another aspect, a liquid transfer device including a housing having a pipette tip; and a plunger assembly disposed within the housing and the pipette tip, wherein a portion of the plunger assembly is configured to engage a fluid reservoir such that the plunger assembly remains stationary relative to the fluid reservoir and the housing moves relative to the plunger assembly.