Science Dojo

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Posted by Ryan On November - 7 - 2008 0 Comment

Charles’ Law

V1/T1 = V2/T2

At constant pressure, the volume of the gas varies directly with the temperature.Thus, as the temperature rises the volume will also rise.

In order for this equation to work, you need to have a constant pressure and use the Kelvin scale when measuring the temperature.If you used any other temperature scale, you would be faced with the problem of negative readings, or, even worse, zero degree measurements.Dividing by zero is something that we just can’t do. After experimentation using a variety of gases, we find that the theoretical point at which gases seem to converge towards zero volume is at -273.150C, or 0 K.We refer to this point as absolute zero and is the basis of the Kelvin Scale.

Demo: Liquid Nitrogen and Balloons

You will see that as the air within the balloons are cooled, the molecules in the balloon begin to move slower and the volume decreases. Notice that as the balloons begin to warm up, they expand towards their original volume.

Here is another example of liquid nitrogen and balloons.

Example:

At constant pressure, 300mL of a gas at 250C is warmed to 350C.Find the new volume.

As the gas warms up, the molecular motion increases.In order for the pressure to stay the same, the volume will have to rise to accommodate the increased motion.

(T2 V1)/T1 = V2

(308 K 300mL)/298 K = V2

310mL = V2

As Charles’ Law predicted, a rise in temperature resulted in a higher volume.

Cool Demo: Gases, Liquid Nitrogen, Clouds, and Thunder

Categories: Gases, States of Matter, Videos

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