Thermodynamics

Question 1

Thermodynamics

Answer 1

The study of heat and its effects

Question 2

Temperature

Answer 2

A measure of the random kinetic energy of the molecules of a substance

Question 3

How do Fahrenheit, Celsius, and Kelvi relate to one another?

Answer 3

Absolute zero: 0 K, -273 degrees Celsius, and -460 degrees Fahrenheit
Freezing Point of Water: 273 K, 0 deg Celsius, and 32 deg Fahrenheit
Boiling Point of Water: 373 K, 100 deg Celsius, and 212 deg Fahrenheit
T(Celsius) = T(Kelvin) - 273
T(Fahrenheit) = 9/5 T(Celsius) + 32

Question 4

Thermal Expansion

Answer 4

ΔL = α L ΔT

Where α is a constant that describes how a specific material’s length changes as temperature changes

Question 5

Volume Expansion

Answer 5

ΔV = β V ΔT, where β = 3α

Question 6

Heat

Answer 6

The energy transferred between two objects as a result of a difference in temperature. Work has to occur in order for heat to transfer from a cooler body to a warmer body.

Question 7

Conduction

Answer 7

Heat transfers through molecular collisions or direct contact. Metals are the best heat conductors due to their mobile electrons, while gases tend to be poor heat conductors.

Question 8

Convection

Answer 8

Heat transfers through the physical motion of the heated material, taking place only in liquids and gases. Heated portions rise while cooler portions sink.

Question 9

Radiation

Answer 9

Heat transfers through electromagnetic radiation.

Question 10

Why do thermos bottles have a shiny surface on the inside?

Answer 10

The shiny surface reflects electromagnetic radiation back into the liquid, slowing down heat loss.

Question 11

Units for heat

Answer 11

1 Calorie = 1000 calories = 3.97 Btu = 4184 J

Question 12

Specific Heat

Answer 12

Q = mc ΔT = mc(T(final) - T(initial))
Q > 0, heat gain
Q < 0, heat loss
This equation should be used when no phase transition occurs.

Question 13

Heat of Transformation

Answer 13

The amount of heat required for a phase change, where q = mL

Question 14

How does temperature change during a phase transition?

Answer 14

Temperature does not change during a phase transition, remaining constant.

Question 15

Heat of Fusion

Answer 15

The heat of transformation corresponding to a phase change involving liquids and solids

Question 16

Heat of Vaporization

Answer 16

The heat of transformation corresponding to a phase change involving liquids and gases

Question 17

Pressure

Answer 17

P = F/ A, where units = Pa = N/ m^2 = kg/ (m s^2)
1 atm = 1.013 X 10^5 Pa
Gas pressure on the container is due to the individual molecular forces the gas exerts on the wall of the container.

Question 18

In problems of thermodynamics, describe the difference between work done BY a gas and work done ON a gas

Answer 18

Work done BY the system is positive, increasing the volume of the gas, while work done ON the system is negative, decreasing the volume of a gas.

Question 19

Work

Answer 19

W = P ΔV

In graphs of P v. V, the total area under the graph is the work done.

Question 20

What is the term for when the pressure remains constant?

Answer 20

Isobaric

Question 21

First Law of Thermodynamics

Answer 21

ΔE = Q - W (remember that W done BY system is + and W done ON system is - and heat absorbed is + while heat lost is -)

Question 22

What are some special cases of the First Law of Thermodynamics?

Answer 22

Adiabatic (Q = 0) ----- ΔU = -W
Constant Volume (W = 0) ----- ΔU = Q
Closed Cycle (ΔU = 0) ----- Q = W

Question 23

When does internal energy increase (ΔU > 0)?

Answer 23

When Q > 0, heat absorbed, and W < 0, work done ON system

Question 24

When does internal energy decrease (ΔU < 0)?

Answer 24

When Q < 0, heat lost, and W > 0, work done BY system

Question 25

Second Law of Thermodynamics

Answer 25

The entropy of a system combined with the surrounding will either increase (for irreversible processes) or not change (for reversible processes)

Question 26

Isothermal Processes

Answer 26

Processes where the temperature remains constant throughout.

Entropy = ΔS = Q/T for reversible, isothermal processes