Concepts of Thermodynamics 1 Flashcards
What is potential energy?
Any form of stored energy
What are some examples of potential energy?
*A raised weight (gravitational)
*A stretched rubber band (elastic)
*A charged battery (chemical)
*A mobile phone that is switched off
(electrical)
What is a kinetic energy?
Energy of moving objects
What are some examples of kinetic energy?
*Electric toaster (radiant)
*Boiling water (thermal)
*A buzzing bee (sound)
*A desk lamp (electrical)
*A bowling ball rolling (mechanical)
What are the three types of systems?
*open system
*closed system
*isolated system
what is the zeroth law of thermodynamics?
“If two systems are in thermal equilibrium with a third system, the
two original systems are in thermal equilibrium with each other”
What type of heat and mass transfer applies for each of the systems?
open: transfer of heat and mass
closed: transfer of mass only
isolated: no transfer
What is the first law of thermodynamics?
“Energy cannot be created or destroyed – it can only be transformed
from one form to another”
what is the equation for first law of thermodynamics?
𝚫U = Q - W
change in internal energy = heat added to system - work done by the system
What are the conditions where Q is positive?
*heat added to the system
*endothermic process
What are the conditions where Q is negative?
*heat released from the system
*exothermic process
What is the equation and conditions in a constant volume (isovolumetric)?
- 𝚫U = q
*no work done on or by the system
*any energy change is result of heat transfer
What is the equation and conditions that apply when in constant temperature (isothermal)?
*q=w
*no change in internal energy
*any heat transferred to the system is used to do work
What is the equation and conditions that apply when no heat transfer (adiabatic)?
*𝚫U = w
*internal energy changes only for work done or received by the system
what are the units of energy?
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
What is enthalpy?
Enthalpy is the measurement of energy in a thermodynamic system (joules)
What is the equation for enthalpy?
𝚫H= 𝚫U + 𝚫(pv)
P= pressure V= volume
𝚫H = 𝚫U and 𝚫U= q so 𝚫H = q
What is the second law of thermodynamics?
“The Universe is always moving towards maximum disorder”
What is entropy (s)?
*measure of disorder
What is the entropy equation (micro states)?
s = kb in W
kb = Boltzmann constant
w= micro states
What is the other entropy equation (all s)?
𝚫s = sf - si
What if there is an increase in the number of micro states?
then Wf > Wi and the entropy of
the system increases ∆S > 0
What if there is a decrease in the number of micro states?
then Wf < Wi and the entropy of the
system decreases ∆S < 0
What is the third law of thermodynamics?
At absolute zero (0 K), the entropy of a perfect, crystalline substance is zero”
Why does entropy equal zero?
all vibrations and atomic movements stop
What temperature is absolute zero?
-273.15 ⁰C
What effect will increasing temperature have on the second law?
- Entropy will be greater as molecules have more kinetic energy and therefore more
dispersion
What effect will mixing particles have on the second law?
- Increases entropy therefore dissolution increases entropy
