The student is measuring the pressure of a gas.
Pressure of a gas can be measured by atm, mm Hg, cm Hg, torr, Pa and bar.
The SI unit of pressure is Pa. The relationship between those units is
1 atm = 760 mm Hg = 76 cm Hg = 760 torr = 1.01325 x 105 Pa = 1.01325 Bar
