Science
The Science domain in this GATE XH guide tests quantitative reasoning in physics, chemistry, and general experimental science. The exam rewards clean unit handling, correct limiting assumptions, and the ability to distinguish a measured quantity from a derived one.
Core rules and concepts
- Use dimensional analysis to check every equation; both sides must have the same base dimensions.
- In stoichiometry, identify the limiting reactant before calculating product mass or moles.
- For ideal gases, PV = nRT; use Kelvin, and match R to the pressure and volume units.
- Thermodynamic sign conventions must be stated: work done by the system and heat absorbed by the system are often positive, but the question may define otherwise.
- Report significant figures consistent with the least precise input, and do not round intermediate steps prematurely.
Worked example
A 0.50 mol sample of an ideal gas occupies 10 L at 300 K. Using R = 0.08314 L·bar·mol⁻¹·K⁻¹, P = nRT/V = (0.50 × 0.08314 × 300)/10 = 1.2471 bar. Rounded to two significant figures, P ≈ 1.2 bar. The calculation fails if 300 K is replaced by 27°C without conversion, because the gas law requires absolute temperature.
Traps that cost marks
Celsius versus Kelvin is the classic error. In stoichiometry, calculating product from the excess reactant gives an impossible yield. In thermodynamics, a work sign error changes ΔU. In data questions, confusing precision with accuracy or ignoring a control can lead to the wrong conclusion. Always carry units through the calculation and ask whether the answer is physically plausible.