the charles’s law

8/8/2019 THE CHARLES’S LAW

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Presented by: Group 3 & 4



Charles's law also known as law of volumes

- is an experimental gas law which describes how gases

tend to expand when heated.



French scientists, Jacques Charles and Joseph-LouisGay-Lussac, made detailed measurements on how the

volume of a gas was affected by the temperature of thegas.

Just as R obert Bo yle made efforts to keep all propertiesof the gas constant except for the pressure and volume,so Jacques Charles took care to keep all properties of the

gas constant except for temperature and volume.



The pressure was held constant by adjusting theheight of mercury so that the two columns of mercury had equal height, and thus the pressure was alwaysequal to the atmospheric pressure.

It is expected that the volume of the gas will increaseas the temperature increases. Is this relationshiplinear? A plot of V T can be used to test this

hypothesis.



y I

f a decrease in temperature results in a decrease in volume, what happens if the temperature is lowered toa point where the volume drops to zero? A negative

volume is obviously impossible, so the temperature at which the volume drops to zero must, in some sense, bethe lowest temperature that can be achieved. Thistemperature is called A bsolute Zero.



y A modern statement of Charles's law is:* At constant pressure, the volume of a given mass of an ideal gas increases or decreases by the same factoras its temperature on the absolute temperature scale

(the gas expands as the temperature increases).

which can be written as:

V T



y where V is the volume of the gas; and T is the absolute

temperature. The law can also be usefully expressed asfollows

V/T = V/T or V/T = T/T1 or VT = VT

- The equation shows that, as absolute temperatureincreases, the volume of the gas also increases inproportion.



CHARLESS LAW FORMULA

Gas Equation: V i/Ti = V f Tf

Initial V olume(V i) = V f Ti / Tf

Initial Temperature(Ti) = V iTf / V f Final V olume(V f ) = V iTf / Ti

Final Temperature(Tf ) = V f Ti / V i where, V i = Initial Volume,T

i= Initial Temperature,

V f = Final Volume. Tf = Final Temperature,



SAMPLE PROBLEMS

A certain amount of gas occupies a volume of 60 L at 300 Ktemperature. Find the temperature of the gas which has a volume of 100 L.

GI VEN: V i = 60 L, Ti = 300 K, V f = 100 L

Step 1: Substitute the values in the below final temperatureequation:

Final Temperature(Tf ) = V f Ti / V i= (100 x 300) / 60

= 30000 / 60Final Temperature(Tf ) = 500 K



Find the final volume of gas at 100 K, if the volume of gas is 5 L at 120 K. V i = 5 L, Ti = 120 K, Tf = 100 K

Step 1: Substitute the values in the below volume

equation:Final Volume(V f ) = V iTf / Ti

= (5 x 100) / 120= 500 / 120F

inal Volume(V f ) = 4.1

67 L



SEA TWOR K1. W hen the temperature of a gas decreases, does the

volume increase or decrease?

2. W hat is the Charless equation for V?

3. W hen 50.0 liters of oxygen at 20.0°C is compressedto 5.00 liters, what is the new temperature?

4. Imagine that a gas occupies a volume of 2.0°C L at atemperature of 27°C . To what temperature indegrees Celsius must the gas be cooled to reduce its

volume to 1.5 L if the pressure is held constant?

the charles’s law

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