A gas occupies a certain volume at 27°C. At what temperature will its volume be twice times the original volume assuming that its pressure remains constant?

Analyze the question: The pressure is constant, and the volume changes with temperature. This is Charles's Law.

Concept: At constant pressure, the volume of a fixed mass of gas is directly proportional to its absolute (Kelvin) temperature:

V₁/T₁ = V₂/T₂

Temperature must always be in Kelvin: T(K) = θ(°C) + 273.

Solution:

• Initial temperature: T₁ = 27 + 273 = 300 K
• Initial volume: V₁ = V
• Final volume: V₂ = 2V (twice the original volume)

Substitute into Charles's Law:

V/300 = 2V/T₂

T₂ = 2 × 300 = 600 K

Convert back to Celsius:

θ = 600 − 273 = 327°C

Answer: The temperature is 327°C, which is option D.

Common mistake: Option A (54°C) comes from doubling the Celsius value (27 × 2). Never do this, because Charles's Law only works with Kelvin temperatures.

Tip: When volume doubles at constant pressure, the Kelvin temperature doubles. So just double the Kelvin value (300 → 600), then subtract 273 to return to °C.