Example Problem with Complete Solution

1C-2 : Identifying Intensive and Extensive Properties 5 pts
State whether each of the following properties is an intensive property or an extensive property. Explain the reasoning behind your answer.
a.) Density
b.) Internal energy
c.) Average molecular weight
d.) Molar volume
e.) Number of moles.
 
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Given:
Find: Intensive or Extensive ?
a.) Density d.) Molar volume
b.) Internal energy e.) Number of moles
c.) Average molecular weight
Assumptions: None.
Equations / Data / Solve: None.
Answers:
a.) Density Intensive
Dividing in half a tank of water at a given T, P and density yields two smaller tanks containing water, but the density of the water in each new, smaller tank is the same as it was intially in the one big tank.
Density is the ratio of mass to volume. The ratio of two extensive properties is an intensive property.
b.) Internal Energy Extensive
Dividing in half a tank of water at a given T, Pwith a given total internal energy yields two smaller tanks containing water at the same T & P, but the internal energy of the water in each new, smaller tank is half as much as it was intially in the one big tank.
c.) Average Molcular Weight Intensive
Dividing in half a tank of air at a given T, P and average molecular weight yields two smaller tanks containing air, but the average molecular weight of the air in each new, smaller tank is the same as it was intially in the one big tank.
Average molecular weight is the ratio of mass to moles. The ratio of two extensive properties is an intensive property.
d.) Molar Volume Intensive
Dividing in half a tank of air at a given T, P and molar volume yields two smaller tanks containing air, but the molar volume of the air in each new, smaller tank is the same as it was intially in the one big tank.
Molar volume is the ratio of volume to moles. The ratio of two extensive properties is an intensive property.
e.) Number of moles Extensive
Dividing in half a tank of water at a given T, P with a givennumber of moles inside yields two smaller tanks containing water at the same T & P, but thenumber of moles of water in each new, smaller tank is half as much as it was intially in the one big tank.