Lesson test: Systems, states and equilibrium

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Systems, states and equilibrium

1.[1p]
What distinguishes a closed system from an isolated one?

A closed system may exchange energy with its surroundings, an isolated one may not

Correct

A closed system has a rigid boundary, an isolated one does not

The answer is: A closed system may exchange energy with its surroundings, an isolated one may not

A closed system may exchange matter, an isolated one may not

The answer is: A closed system may exchange energy with its surroundings, an isolated one may not

A closed system is always in equilibrium, an isolated one need not be

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.

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 $100$ 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 $100$ degrees Celsius: phase equilibrium

3.[2p]
Why is density an intensive property?

It is the ratio of two extensive properties, so the scaling cancels

Correct

It is measured per unit volume rather than per unit mass

The answer is: It is the ratio of two extensive properties, so the scaling cancels

It is fixed for any given substance

The answer is: It is the ratio of two extensive properties, so the scaling cancels

It appears in the ideal gas equation

The answer is: It is the ratio of two extensive properties, so the scaling cancels

4.[2p]
Air behaves as an ideal gas with $R = 287$ J kg⁻¹ K⁻¹. What is its specific volume, in m³ kg⁻¹, at $200$ kPa and $300$ K?

CorrectNot quite: 0.4305

5.[2p]
Pressure and temperature are independent properties for water and steam coexisting at $100$ degrees Celsius.

True

The answer is: False

False

Correct

6.[2p]
The state postulate says two independent intensive properties fix the state of a simple compressible system. What does "simple compressible" exclude?

Systems with work modes other than expansion and compression

Correct

Systems containing more than one phase

The answer is: Systems with work modes other than expansion and compression

Systems whose density changes during a process

The answer is: Systems with work modes other than expansion and compression

Systems that are not in thermal equilibrium

The answer is: Systems with work modes other than expansion and compression

7.[2p]
Which of these prevent a process from being reversible?

Select all that apply

Friction between the piston and the cylinder wall

Correct

Heat flow across a finite temperature difference

Correct

Unrestrained expansion into an evacuated space

Correct

Being carried out at constant pressure

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 $150$ kPa from $0.010$ m³ to $0.050$ m³. How much work does it do, in kJ?

CorrectNot quite: 6.0

9.[3p]
Two different quasi-static paths join the same two states on a $p$ - $V$ diagram. What does the area enclosed between them represent?

The difference in the work done along the two paths

Correct

The change in volume between the two states

The answer is: The difference in the work done along the two paths

The heat rejected on the return path

The answer is: The difference in the work done along the two paths

The change in pressure between the two states

The answer is: The difference in the work done along the two paths

10.[3p]
A freely sliding piston of mass $80$ kg and face area $0.020$ m² closes a vertical cylinder, with atmospheric pressure $100$ kPa above it. Take $g = 9.807$ m s⁻². What is the absolute pressure of the gas beneath it, in kPa?

CorrectNot quite: 139.2

1.[1p] What distinguishes a closed system from an isolated one?

2.[2p] Match each situation to what it is an example of.

3.[2p] Why is density an intensive property?

4.[2p] Air behaves as an ideal gas with R=287 J kg⁻¹ K⁻¹. What is its specific volume, in m³ kg⁻¹, at 200 kPa and 300 K?

5.[2p] Pressure and temperature are independent properties for water and steam coexisting at 100 degrees Celsius.

6.[2p] The state postulate says two independent intensive properties fix the state of a simple compressible system. What does "simple compressible" exclude?

7.[2p] Which of these prevent a process from being reversible?

8.[2p] A gas expands quasi-statically at a constant 150 kPa from 0.010 m³ to 0.050 m³. How much work does it do, in kJ?

9.[3p] Two different quasi-static paths join the same two states on a p-V diagram. What does the area enclosed between them represent?

10.[3p] A freely sliding piston of mass 80 kg and face area 0.020 m² closes a vertical cylinder, with atmospheric pressure 100 kPa above it. Take g=9.807 m s⁻². What is the absolute pressure of the gas beneath it, in kPa?

1.[1p]
What distinguishes a closed system from an isolated one?

2.[2p]
Match each situation to what it is an example of.

3.[2p]
Why is density an intensive property?

4.[2p]
Air behaves as an ideal gas with $R = 287$ J kg⁻¹ K⁻¹. What is its specific volume, in m³ kg⁻¹, at $200$ kPa and $300$ K?

5.[2p]
Pressure and temperature are independent properties for water and steam coexisting at $100$ degrees Celsius.

6.[2p]
The state postulate says two independent intensive properties fix the state of a simple compressible system. What does "simple compressible" exclude?

7.[2p]
Which of these prevent a process from being reversible?

8.[2p]
A gas expands quasi-statically at a constant $150$ kPa from $0.010$ m³ to $0.050$ m³. How much work does it do, in kJ?

9.[3p]
Two different quasi-static paths join the same two states on a $p$ - $V$ diagram. What does the area enclosed between them represent?

10.[3p]
A freely sliding piston of mass $80$ kg and face area $0.020$ m² closes a vertical cylinder, with atmospheric pressure $100$ kPa above it. Take $g = 9.807$ m s⁻². What is the absolute pressure of the gas beneath it, in kPa?