Concepts of Thermodynamics 1

Question 1

What is potential energy?

Answer 1

Any form of stored energy

Question 2

What are some examples of potential energy?

Answer 2

*A raised weight (gravitational)
*A stretched rubber band (elastic)
*A charged battery (chemical)
*A mobile phone that is switched off
(electrical)

Question 3

What is a kinetic energy?

Answer 3

Energy of moving objects

Question 4

What are some examples of kinetic energy?

Answer 4

*Electric toaster (radiant)
*Boiling water (thermal)
*A buzzing bee (sound)
*A desk lamp (electrical)
*A bowling ball rolling (mechanical)

Question 5

What are the three types of systems?

Answer 5

*open system
*closed system
*isolated system

Question 6

what is the zeroth law of thermodynamics?

Answer 6

“If two systems are in thermal equilibrium with a third system, the
two original systems are in thermal equilibrium with each other”

Question 7

What type of heat and mass transfer applies for each of the systems?

Answer 7

open: transfer of heat and mass
closed: transfer of mass only
isolated: no transfer

Question 8

What is the first law of thermodynamics?

Answer 8

“Energy cannot be created or destroyed – it can only be transformed
from one form to another”

Question 9

what is the equation for first law of thermodynamics?

Answer 9

𝚫U = Q - W
change in internal energy = heat added to system - work done by the system

Question 10

What are the conditions where Q is positive?

Answer 10

*heat added to the system
*endothermic process

Question 11

What are the conditions where Q is negative?

Answer 11

*heat released from the system
*exothermic process

Question 12

What is the equation and conditions in a constant volume (isovolumetric)?

Answer 12

• 𝚫U = q
  *no work done on or by the system
  *any energy change is result of heat transfer

Question 13

What is the equation and conditions that apply when in constant temperature (isothermal)?

Answer 13

*q=w
*no change in internal energy
*any heat transferred to the system is used to do work

Question 14

What is the equation and conditions that apply when no heat transfer (adiabatic)?

Answer 14

*𝚫U = w
*internal energy changes only for work done or received by the system

Question 15

what are the units of energy?

Answer 15

SI unit = joule (J), will also see calories (cal / kcal)
1 cal = heat needed to raise the temperature of 1 gram of water 1⁰C at standard pressure 1 cal = 4.184 J, 1 kcal = 4184 J

Question 16

What is enthalpy?

Answer 16

Enthalpy is the measurement of energy in a thermodynamic system (joules)

Question 17

What is the equation for enthalpy?

Answer 17

𝚫H= 𝚫U + 𝚫(pv)
P= pressure V= volume

𝚫H = 𝚫U and 𝚫U= q so 𝚫H = q

Question 18

What is the second law of thermodynamics?

Answer 18

“The Universe is always moving towards maximum disorder”

Question 19

What is entropy (s)?

Answer 19

*measure of disorder

Question 20

What is the entropy equation (micro states)?

Answer 20

s = kb in W
kb = Boltzmann constant
w= micro states

Question 21

What is the other entropy equation (all s)?

Answer 21

𝚫s = sf - si

Question 22

What if there is an increase in the number of micro states?

Answer 22

then Wf > Wi and the entropy of
the system increases ∆S > 0

Question 23

What if there is a decrease in the number of micro states?

Answer 23

then Wf < Wi and the entropy of the
system decreases ∆S < 0

Question 24

What is the third law of thermodynamics?

Answer 24

At absolute zero (0 K), the entropy of a perfect, crystalline substance is zero”

Question 25

Why does entropy equal zero?

Answer 25

all vibrations and atomic movements stop