Chapter 6 Flashcards
(97 cards)
thermochemistry
describes the heat energy changes occurring during chemical reactions and physical transformations
potential and kinetic energy analogy
ball on ledge has potential energy (not kinetic)
chemical energy
a form of potential energy associated with positions of electrons and nuclei in a system
chemical energy can be found in what?
atoms
molecules
ionic compounds
condensed phases
system
the area you are studying
surroundings
everything else outside the system
what are the 3 types of systems?
open system
closed system
isolated system
what is an example of an open, closed and isolated system?
open system: open pot of boiling water
closed system: closed pot of water (no volume change)
isolated system: a thermos bottle with the lid screwed on tight
what is the law of conservation of energy/ the first law of thermodynamics?
energy can neither be created nor destroyed; rater, it can only be transformed or transferred from one object to another
what is the equation for internal energy?
ΔU = U final - U initial
what does Δ mean?
change in
what is the equation for change in internal energy of the universe?
ΔU = ΔU system + ΔU surr
surr= surroundings
according to the law of conservation of the energy what does ΔU universe equal?
0
what does ΔU sys equal?
ΔU sys = -ΔU surr or. -ΔU sys = ΔU surr
always has opposite signs because one is losing and one is gaining
energy lost by the system exactly equals energy gained by the surroundings
you pay tuition for university, the university receives money, what are the signs for each?
pay tuition (-)
university gains $ (+)
-ΔU sys = ΔU surr
heat
written as q
the flow of energy caused by a temperature difference (from hot object to cold)
work
written as w
the energy required to move something against a force
a force acting through a distance
ex. when you push a chair its work and therefore, would be (-)
internal energy change of the system is the sum of the heat transferred and the work done, how is this equation written?
ΔU = q + w
absolute temperature (T)
is different for the celsius and kelvin scales
0°C = 273.15 K
difference in temperature
ΔT is teh same for the celsius and kelvin scales
an increase of 10°C = an increase of 10 K
115.0 J of heat and 77.0 kJ of work, what is internal energy in KJ?
-76.9kJ
*slide 21 lecture 2-3
how do you calculate temperature?
ΔT = T final - T initial
what does q depend on?
the identity of material (ability to absorb heat)
heat capacity
written as C
quantity of heat required to change the temperature of the system by 1°C or 1K
(depends on mass of the heated object)