| English | Charles's law |
|---|---|
| Bahasa Melayu | Hukum Charles |
| 中文 | 查理定律 |
Definition
For a fixed mass of gas at constant pressure, the volume is directly proportional to its absolute temperature.
In exam terms
Charles's law states that for a fixed mass of gas at constant pressure, the volume is directly proportional to its absolute temperature. In symbols, V/T = constant, or V₁/T₁ = V₂/T₂, where V is volume in m³ and T is absolute temperature in kelvin (K).
When the gas is heated, its particles move faster and would strike the walls harder, so the gas expands to keep the pressure constant. The temperature must be in kelvin.
Worked line: V₁/T₁ = V₂/T₂ → (2.0 m³)/(300 K) = V₂/(450 K), so V₂ = 3.0 m³. Example of correct use: by Charles's law, warming a gas at constant pressure increases its volume in proportion to its absolute temperature.
Do not confuse it with…
Do not confuse Charles's law with Boyle's law or the pressure law. Charles's law keeps the pressure constant (volume against temperature), Boyle's law keeps the temperature constant (pressure against volume), and the pressure law keeps the volume constant (pressure against temperature).
In Paper 2 this is usually asked as state Charles's law, a V against T calculation, or a graph. The temperature must always be converted to kelvin using T/K = θ/°C + 273; using degrees Celsius directly is the most common error and gives the wrong ratio.
Source: DSKP KSSM Physics Form 4 and 5 (Versi English) (Bahagian Pembangunan Kurikulum (BPK), KPM)