in Boyle's law?

Analyze the question: The question is cut off ("in Boyle's law?"), but the options show it is asking what Boyle's law states about the relationship between pressure (P), volume (V) and temperature (T).

Concept: Boyle's law says that for a fixed mass of gas at constant temperature, the volume of the gas is inversely proportional to its pressure.

Mathematically:

• V ∝ 1/P (at constant T)
• PV = constant
• P₁V₁ = P₂V₂

Checking each option:

• A. T is constant, P varies directly with V. Wrong, because the relationship is inverse, not direct.
• B. P is constant, V varies inversely with T. Wrong. At constant pressure, V is directly proportional to T. That is Charles' law.
• C. V is constant, P varies directly with T. This is true, but it is the Pressure law (Gay-Lussac's law), not Boyle's law.
• D. T is constant, V varies inversely with P. Correct. This is exactly Boyle's law.

Answer: D.

Tip: Remember "Boyle = Backwards (inverse) at constant Temperature." You can also remember the three gas laws this way:

• Boyle: T constant, P and V are inverse.
• Charles: P constant, V and T are direct.
• Pressure law: V constant, P and T are direct.