Charles' Law NEET Cheat Sheet: Everything You Need
Charles' LawGas LawsStates of MatterNEET ChemistryNEET 2025V-T relationshipideal gas
Charles' Law NEET Cheat Sheet: Everything You Need
States of Matter (Gases & Liquids)·2 min read·NEET 2026
What NEET Asks
Conceptual understanding of V-T relationship at constant pressure.
Direct calculations involving changes in volume or temperature.
Graphical representation of Charles' Law.
Often combined with other gas laws or ideal gas equation.
Key Points
Charles' Law: States that at constant pressure and number of moles, the volume of a given mass of gas is directly proportional to its absolute temperature.
Mathematical Form: V ∝ T or V/T = constant.
Combined Form: V₁/T₁ = V₂/T₂.
Temperature Unit: Always use Kelvin (K). T(K) = t(°C) + 273.15 (or 273 for NEET calculations).
Graphical Representation: A plot of V vs T(K) is a straight line passing through the origin. A plot of V vs t(°C) is a straight line extrapolating to -273.15°C (absolute zero) on the temperature axis.
Absolute Zero: The theoretical temperature (-273.15°C or 0 K) at which an ideal gas would have zero volume.
Must-Know Formula / Reaction
V₁/T₁ = V₂/T₂
V: Volume of the gas (e.g., L, mL)
T: Absolute temperature (Kelvin, K)
Common Mistakes
Students often forget to convert Celsius temperature to Kelvin before applying the formula.
Don't confuse Charles' Law (V-T relationship) with Boyle's Law (P-V relationship).
Students sometimes incorrectly assume that a V vs t(°C) graph passes through the origin.
Rapid Revision
Charles' Law: V/T = constant (P, n constant). Temperature must be in Kelvin. V vs T(K) is linear through origin. Absolute zero is -273.15°C. Remember: V₁/T₁ = V₂/T₂.
Frequently Asked Questions
What is the key statement of Charles' Law?▾
Charles' Law states that for a fixed mass of gas at constant pressure, the volume of the gas is directly proportional to its absolute temperature. This means as temperature increases, volume increases proportionally.
Why is it important to use Kelvin temperature in Charles' Law calculations?▾
Kelvin is the absolute temperature scale, where 0 K represents absolute zero, the theoretical temperature at which a gas would have zero volume. Using Celsius would lead to incorrect proportionality and potential negative volumes, which are physically impossible.
What does the graph of Volume vs. Temperature look like for Charles' Law?▾
When volume is plotted against absolute temperature (Kelvin), it results in a straight line passing through the origin (0,0). If plotted against Celsius temperature, it's a straight line that extrapolates to -273.15°C on the temperature axis when volume is zero.
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