This all-in-one online Charles’ Law Calculator performs calculations using the Charles’ law formula that relates the initial and final volume and temperature values of an ideal gas at the same constant pressure. You can enter the values of any three parameters in the fields of the calculator and find the missing parameter.
V1 / T1 = V2 / T2
What is Charles’ Law?
Charles’ law is an experimental gas law that relates the volume and temperature of a fixed mass of a gas that is close to an ideal gas when its pressure remains constant. The law was named after scientist Jacques Charles, who first formulated the original law.
The modern formulation of Charles’ law states that when the pressure on a sample of a dry gas is held constant, the Kelvin temperature and the volume will be in direct proportion. This relationship of direct proportion can be written as the following Charles’ law formula:
$$V = k \cdot T,$$
where
• \(V \ \) is the volume of the gas,
• \(T \ \) is the temperature of the gas (measured in Kelvins),
• \(k \ \) is a non-zero constant.
The Charles’s law is often expressed in the following form:
$$\frac{V_1}{T_1} = \frac{V_2}{T_2},$$
where
• \(V_1 \ \) is the initial volume,
• \(T_1 \ \) is the initial temperature (in Kelvins),
• \(V_2 \ \) is the final volume,
• \(T_2 \ \) is the final temperature (in Kelvins).
It should be emphasized that the above formulas use temperature measured in Kelvin. Recall that the Kelvin is the SI unit for temperature and is sometimes referred to as absolute temperature. If you want to use other temperature units, you must use the following conversion formulas:
$$Celsius = Kelvin \ – \ 273.15,$$
$$Fahrenheit = \frac{9}{5} \cdot Celsius + 32.$$
These conversions are done automatically when you use our Charles’ Law calculator and select the units you need.
When using the Charles’s law, remember that it only applies to gases that are close to an ideal gas. An ideal gas consists of particles of negligibly small size that do not interact with each other. The ideal gas model makes it easy to understand the physical meaning of Charles’s law.
Indeed, an increase in the temperature of a gas causes individual gas molecules to move faster. The faster the molecules move, the more often and with greater force they collide with the walls of the gas container. More frequent and forceful collisions result in higher pressure. However, if the volume of the container is adjustable, the volume will increase while the pressure remains the same. The thermodynamic process in which the pressure in the system is maintained constant is called isobaric.
This happens because, despite the increased average velocity of the molecules, the frequency of collisions with the walls decreases. This, in turn, is due to an increase in the average path length of a molecule before it collides with the wall due to an increase in volume. As a result, the pressure is kept constant.
The reverse process occurs when the gas temperature decreases. As can be seen from the above formula, when the temperature decreases to zero, the volume of the gas also tends to zero. The temperature of 0 K = -273.15 ºC is called absolute zero. According to classical physics, at this temperature all motion ceases. It is clear that at this temperature the volume of an ideal gas, consisting of particles that have no size, will be zero.
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