- #1
Ahsan Khan
- 270
- 5
Hello guys
In my previous tags come up with some molecular description of substances. And it has been suggested that temperature, a degree of hotness or coldness is basically, a direct indication of the average kinetic energy of the molecules the body made of. After a deeper look toward this saying it creates some confusion to me. The theory behind the confusion lies in three things.
1. Temperature is a direct measure of average kinetic energy of the molecules a body has.
2. different things may have different degrees of freedom and in each degree of freedom molecule has posses same energy equal to 1/2κT.
3. Gases having different degree of freedom have different specific heats.
By assuming that temperature is a measure of the average kinetic energy of the molecules, we must say the different gasses at the same temperature must have same average kinetic energy. TRUE?
Now consider the following-
I take two gasses one monoatomic ( having 3 degree of freedom) and other diatomic (having 5 degree of freedom) in two separate and closed containers initially at the same temperature, they therefore will have same number of moles(avagadro's law). As such the monoatomic gas has specific heat 3/2R and the diatomic one has 5/2R. Because ΔT=Q/(nCv), it means when same amount of heat Q (energy) is given to these gases the rise in temperature in the gasses will be different. TRUE?
Also as such the volume of the gas remains constant, no work is done by the gas and as per the first law of thermodynamic the entire heat must be used to raise the internal energy.As such this energy now get stored as kinetic energy of the gas.TRUE?
Drawn conclusion- by giving same heat ,same amount of energy per molecule has been increased TRUE? these gasses initially had same temperature and therefore initially there molecules must same average kinetic energy now equal amount of kinetic energy has been raised by giving same heat.But from ΔT=Q/(nCv), ΔT is found to be different for the two gasses and thus their final temperature must be different(as initially they have same temperature. So the molecules of the two gasses at the second state have same average kinetic energy but different temperature. From this it appears as the excess (2 vibrational) degrees have just consumed heat and their increases in kinetic energy contribute nothing to temperature.This very observation forces me not to accept that temperature as a measure of the average kinetic energy of molecules of the body. i will be very thankfull if somebody clear this to me. REGARDS!
In my previous tags come up with some molecular description of substances. And it has been suggested that temperature, a degree of hotness or coldness is basically, a direct indication of the average kinetic energy of the molecules the body made of. After a deeper look toward this saying it creates some confusion to me. The theory behind the confusion lies in three things.
1. Temperature is a direct measure of average kinetic energy of the molecules a body has.
2. different things may have different degrees of freedom and in each degree of freedom molecule has posses same energy equal to 1/2κT.
3. Gases having different degree of freedom have different specific heats.
By assuming that temperature is a measure of the average kinetic energy of the molecules, we must say the different gasses at the same temperature must have same average kinetic energy. TRUE?
Now consider the following-
I take two gasses one monoatomic ( having 3 degree of freedom) and other diatomic (having 5 degree of freedom) in two separate and closed containers initially at the same temperature, they therefore will have same number of moles(avagadro's law). As such the monoatomic gas has specific heat 3/2R and the diatomic one has 5/2R. Because ΔT=Q/(nCv), it means when same amount of heat Q (energy) is given to these gases the rise in temperature in the gasses will be different. TRUE?
Also as such the volume of the gas remains constant, no work is done by the gas and as per the first law of thermodynamic the entire heat must be used to raise the internal energy.As such this energy now get stored as kinetic energy of the gas.TRUE?
Drawn conclusion- by giving same heat ,same amount of energy per molecule has been increased TRUE? these gasses initially had same temperature and therefore initially there molecules must same average kinetic energy now equal amount of kinetic energy has been raised by giving same heat.But from ΔT=Q/(nCv), ΔT is found to be different for the two gasses and thus their final temperature must be different(as initially they have same temperature. So the molecules of the two gasses at the second state have same average kinetic energy but different temperature. From this it appears as the excess (2 vibrational) degrees have just consumed heat and their increases in kinetic energy contribute nothing to temperature.This very observation forces me not to accept that temperature as a measure of the average kinetic energy of molecules of the body. i will be very thankfull if somebody clear this to me. REGARDS!