Systems, states and equilibrium
1.[1p] What distinguishes a closed system from an isolated one?
What distinguishes a closed system from an isolated one?
The answer is: A closed system may exchange energy with its surroundings, an isolated one may not
The answer is: A closed system may exchange energy with its surroundings, an isolated one may not
The answer is: A closed system may exchange energy with its surroundings, an isolated one may not
2.[2p] Match each situation to what it is an example of.
Match each situation to what it is an example of.
A kettle boiling with the lid off
A sealed can of soup heated in a pan
Coffee in a good vacuum flask
Water and steam coexisting at degrees Celsius
an isolated system
a closed system
phase equilibrium
an open system
Show the answer
A kettle boiling with the lid off: an open system A sealed can of soup heated in a pan: a closed system Coffee in a good vacuum flask: an isolated system Water and steam coexisting at degrees Celsius: phase equilibrium
3.[2p] Why is density an intensive property?
Why is density an intensive property?
The answer is: It is the ratio of two extensive properties, so the scaling cancels
The answer is: It is the ratio of two extensive properties, so the scaling cancels
The answer is: It is the ratio of two extensive properties, so the scaling cancels
4.[2p] Air behaves as an ideal gas with J kg⁻¹ K⁻¹. What is its specific volume, in m³ kg⁻¹, at kPa and K?
Air behaves as an ideal gas with J kg⁻¹ K⁻¹. What is its specific volume, in m³ kg⁻¹, at kPa and K?
5.[2p] Pressure and temperature are independent properties for water and steam coexisting at degrees Celsius.
Pressure and temperature are independent properties for water and steam coexisting at degrees Celsius.
The answer is: False
6.[2p] The state postulate says two independent intensive properties fix the state of a simple compressible system. What does "simple compressible" exclude?
The state postulate says two independent intensive properties fix the state of a simple compressible system. What does "simple compressible" exclude?
The answer is: Systems with work modes other than expansion and compression
The answer is: Systems with work modes other than expansion and compression
The answer is: Systems with work modes other than expansion and compression
7.[2p] Which of these prevent a process from being reversible?
Which of these prevent a process from being reversible?
Select all that apply
The answer is: Friction between the piston and the cylinder wall, Heat flow across a finite temperature difference, Unrestrained expansion into an evacuated space
8.[2p] A gas expands quasi-statically at a constant kPa from m³ to m³. How much work does it do, in kJ?
A gas expands quasi-statically at a constant kPa from m³ to m³. How much work does it do, in kJ?
9.[3p] Two different quasi-static paths join the same two states on a - diagram. What does the area enclosed between them represent?
Two different quasi-static paths join the same two states on a - diagram. What does the area enclosed between them represent?
The answer is: The difference in the work done along the two paths
The answer is: The difference in the work done along the two paths
The answer is: The difference in the work done along the two paths
10.[3p] A freely sliding piston of mass kg and face area m² closes a vertical cylinder, with atmospheric pressure kPa above it. Take m s⁻². What is the absolute pressure of the gas beneath it, in kPa?
A freely sliding piston of mass kg and face area m² closes a vertical cylinder, with atmospheric pressure kPa above it. Take m s⁻². What is the absolute pressure of the gas beneath it, in kPa?