Physics

 

 

Charles Law

The volume of a fixed mass of gas is directly proportional to its temperature at constant pressure.

Please move the slider and experiment with it.

V ∝ T

 

v ∝ t
v = k t
v = k t

As you can see, the line, when extended backwards crosses the x-axis at -273 C⁰. There is a special temperature when all gases have zero volume, called Absolute Temperature.
So, 0 T = -273 C
+ 273 => 273 T = 0C
+ t => (273 + t) T = t C
T = 273 + t, where t is the temperature in Celsius.

If the temperature and volume of a fixed mass of gas take the values of v₁ T₁and V₂ T₂ respectively, where T is absolute temperature,

V₁ / T₁ = V₂ / T₂

E.g.

The volume of a fixed mass of air is volume is 8 cm³ at 27 C⁰. Its temperature is raised to 127 C⁰, while keeping the pressure constant. Find the volume.

p₁ = 20, v₁ = 8, p₂ = 40
According to Charles's law,
V₁ / T₁ = V₂ / T₂
8 / (273 + 27) = v₂ / (273 + 127)
v₂ = 10.6cm³

Please answer the following questions.

1. The volume of a gas at 30C⁰ is 8 cm³. Find its volume when the temperature is 50C⁰ while pressure remains the same.
2. The volume of a gas at constant temperature is plotted against temperature in Celsius. What do the gradient and intercept represent ?
3. The volume of a gas at 30C⁰ is x cm³. Find x when the temperature is 50C⁰ while pressure remains the same.