Charles's Law Calculator
Calculate volume or temperature using Charles's law (constant pressure).
About Charles's Law Calculator
Charles's law: at constant pressure, volume is directly proportional to absolute temperature.
$$\frac{V_1}{T_1} = \frac{V_2}{T_2}$$
How to use this calculator
- Enter the known starting volume and temperature, then the final temperature or final volume.
- Make sure temperatures are in Kelvin, because Charles's law only works with absolute temperature.
- Choose the value you want to find, either final volume or final temperature.
- Read the result, then check whether it makes sense, warmer gas should take up more space.
The formula explained
Charles's law uses the ratio \(\frac{V_1}{T_1} = \frac{V_2}{T_2}\) to relate a gas's volume and temperature when pressure is constant. It can be rearranged to find \(V_2\) or \(T_2\), depending on which value is missing.
- \(V_1\) = initial volume
- \(T_1\) = initial temperature in Kelvin
- \(V_2\) = final volume
- \(T_2\) = final temperature in Kelvin
Step by step method
- Write down the known values and convert any temperature in Celsius to Kelvin using \(K = ^\circ C + 273.15\).
- Substitute the values into \(\frac{V_1}{T_1} = \frac{V_2}{T_2}\).
- Solve for the unknown by cross multiplying, then check that the answer matches the situation.
Worked example
Problem. A gas has a volume of \(2.4\\,L\) at \(300\\,K\). If the temperature increases to \(360\\,K\) at constant pressure, what is the new volume?
- Use Charles's law, \(\frac{V_1}{T_1} = \frac{V_2}{T_2}\).
- Substitute the values, \(\frac{2.4}{300} = \frac{V_2}{360}\). Solve to get \(V_2 = 2.88\\,L\).
- The volume increases because the temperature increased.
Answer. \(2.88\\,L\)
Tips and common mistakes
- Always use Kelvin, not Celsius, or the ratio will be wrong.
- If the temperature goes up, the volume should also go up, so use that to check your work.
Frequently asked questions
How do I use a Charles's Law calculator to find the new volume or temperature?+
Enter the known values for initial volume, initial temperature, and the final value you already know, then choose whether you want to solve for the new volume or the new temperature. This calculator uses Charles's law at constant pressure, so the temperatures should be in Kelvin for the result to be physically correct.
What does the formula V1/T1 = V2/T2 mean?+
It means that for a gas at constant pressure, volume is directly proportional to absolute temperature. If temperature increases, volume increases by the same ratio, as long as the gas amount and pressure stay the same.
Do I need to convert Celsius to Kelvin before using Charles's law?+
Yes, because Charles's law uses absolute temperature, not Celsius. Convert by adding 273.15 to each Celsius value before calculating, for example 25 C becomes 298.15 K.
What happens if I use 0 C or a negative Celsius temperature?+
You can use temperatures below 0 C only after converting them to Kelvin, as long as the Kelvin value stays above zero. You cannot use 0 K or negative Kelvin in this law because absolute temperature cannot be zero or negative.
How is Charles's law different from Boyle's law or the combined gas law?+
Charles's law changes volume and temperature while keeping pressure constant. Boyle's law relates pressure and volume at constant temperature, and the combined gas law is used when pressure is not constant and you need all three variables together.
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