Thermodynamics and Gases

Question 1

What is internal energy?

Answer 1

The sum of all energies of all the molecules in a substance.

Question 2

What is temperature?

Answer 2

Related to the average kinetic energy per molecule of a substance.

Question 3

What is power?

Answer 3

Work per time.

Question 4

What is conduction?

Answer 4

The physical transfer of atomic vibration energy from one atom to another.

Question 5

What is convection?

Answer 5

Convectionn is the transfer of thermal energy fromm one place to another through fluid flow.

Question 6

What is radiation?

Answer 6

The transfer of energy through electromagnetic waves.

Question 7

What is the first law of thermodynamics?

Answer 7

A statement of conservation of energy.

ΔU = Q + W

Question 8

What is the sign of Q is heat is added to a gas?

Answer 8

Positive

Question 9

What is the sign of Q is heat is taken from a gas?

Answer 9

Negative

Question 10

What happens to ΔU if the internal temperature of a gas rises?

Answer 10

ΔU is positive

Question 11

What does positive W mean?

Answer 11

Work is done ON a gas

Question 12

What does negative W mean?

Answer 12

Work is done by a gas. An example would be a gas’s volume increasing.

Question 13

What does a higher PV mean in terms of temperature?

Answer 13

The temperature will be higher. This is due to PV=nRT

Question 14

What is an isothermal line?

Answer 14

The lines on a P vs V graph, which have the same value of PV. Because these points have the same PV they also share the same T.

Question 15

What shape does an isothermal line make?

Answer 15

A hyperbola

Question 16

What does moving to the right on a P vs V graph mean?

Answer 16

Negative work

Question 17

What does moving to the left on a P vs V graph mean?

Answer 17

Positive work

Question 18

What happens when you move up or down on a P vs V graph?

Answer 18

No work is done, as the volume does not change. Work requires motion.

Question 19

How is work related to pressure and volume mathematically?

Answer 19

W = -PΔV

Question 20

What does the area under a P vs V graph mean?

Answer 20

A larger area means a larger magnitude of work has been done.

Question 21

What is the temperature change in a cycle?

Answer 21

0, as temperature change relies on PV. If PV doesn’t change, neither does T.

Question 22

How does one find the net work in a cycle?

Answer 22

By finding the area INSIDE of the cycle.

Question 23

What are the four special processes on a PV diagram?

Answer 23

Isobaric, Isochoric/Isovolumetric, Isothermal, and Adiabatic

Question 24

When is a path isobaric?

Answer 24

When pressure remains the same.

Question 25

What does an isobaric path look like?

Answer 25

The graph moves left or right.

Question 26

When is a path Isochoric/Isovolumetric?

Answer 26

When volume remains constant.

Question 27

What does an isochoric/isovolumetric path look like?

Answer 27

The graph moves up or down.

Question 28

When is a path adiabatic?

Answer 28

No heat transfer between the system and the enviroment takes place.

Question 29

What does an adiabatic path look like?

Answer 29

Curved path, similar to isothermal but steeper.

Question 30

What is the second law of thermodynamics?

Answer 30

The entropy of a system cannot decrease unless work is done on that system.

Question 31

What is entropy?

Answer 31

A thermodynamic quantity representing the unavailability of a system’s thermal energy for conversion into mechanical work, often interpreted as the degree of disorder or randomness in the system.