Lecture 5 - Effect of Temperature on Volume of a Gas, at constant Pressure

ACKNOWLEDGEMENT:

Figure	Source of Figure
Figure 8a	https://prezi.com/myiigflss0gg/charless-law/
Figure 8b	https://prezi.com/myiigflss0gg/charless-law/
Figure 8c	www.physics-reference.com

Gases & the effect of temperature and pressure on their volumes:

The particles of the gas are far apart, moving in random directions with their K.E. Therefore, there are large empty spaces between the particles which gives the gases their compressibility. For a fixed volume of gas in a gas jar, the volume of a gas is affected by temperature and pressure.

Absolute Temperature:

Absolute temperature is -273°C or 0 Kelvin; K. It is theoretically the lowest and coldest temperature possible and 0 Kelvin is called as Absolute Zero. At this temperature the particles of matter have minimal or no energy and motion.

The size of the Kelvin and Celsius scale is same so all temperatures in Celsius can be converted to their Kelvin values by adding 273. All Kelvin temperatures can be converted to Celsius by subtracting 273.

Temperature in Kelvin = Temperature in Celsius + 273

Temperature in Celsius = Temperature in Kelvin – 273

0°C = 273K

-273°C = 0K 

Temperature – Volume Graph:

Temperature – Pressure Graph:

At absolute temperature, all gases have a volume and pressure of 0cm3 and 0atm, respectively; provided they maintain their gaseous state. However, all real gases condense to their liquid state before absolute temperature. Helium with the lowest boiling point -269, converts to liquid helium.

Case 1: Effect of temperature on Volume of a gas, at Constant Pressure:

Figure 8a:

Figure 8b:

Figure 8a shows a gas jar containing a certain volume of gas V1 at a temperature of T1. The piston exerts a constant pressure P on the Volume V1. The gas is heated to a temperature T2. As the gas is heated, the particles of the gas gain K.E and they start moving with greater velocities and K.E. The start striking/colliding against the piston and to maintain the pressure P, the piston rises; INCREASING the volume of the gas to V2.

Therefore, it can be concluded that gases expand on heating.

Charles’ Law stated this effect as:

“The Volume of a gas is directly proportional to its absolute Temperature, at Constant Pressure.”

Mathematically:

Graphically: Figure 8c