u1: thermodynamics Flashcards
thermodynamics
area of physical science concerned with studying the relationships between heat, work, temperature, and energy
thermochemistry
study of energy changes, namely heat energy, associated with transformations like chemical reactions and phase changes
3 kinds of changes in matter
chemical, physical, and nuclear
physical change
change in the form of a substance (no chemical bonds broken)
chemical change
change in chemical bonds between atoms: results in rearrangement of atoms to form new substances
nuclear change
change in the protons or neutrons in an atom resulting in formation of new atoms
major types of energy
- kinetic energy
- potential energy
where is energy stored in chemicals
chemical bonds
how is kinetic energy measured
temperature (specifically change in temperature)
energy
- a property of matter and radiation which is the ability to form work
- such as: causing motion, interaction of molecules
- all matter has kinetic and potential energy
potential energy
energy that is stored in an object
kinetic energy
energy of motion
two ways to transfer energy
- heat (Q): transfer of energy between two objects due to temperature difference
- work (w): force acting over a distance (when force acts on object and object undergoes displacement)
temperature
measure of the average kinetic energy of particles
heat
amount of thermal energy transferred between substances, systems, or surroundings
endothermic
- energy absorbed by substance/bond/nucleus
- temperature of surroundings drops
exothermic
- energy released from substance/bond/nucleus
- temperature of surroundings increases
first law of thermodynamics
- energy is neither created nor destroyed but transformed and transferred
- ΔE(universe)= 0 = ΔE(system) + ΔE(surroundings)
- ΔE(surroundings) = -ΔE(system)
enthalpy equation
- H = E(system) + PV
- so, ΔH = ΔE(system) + PV
- but PV at contant pressure and volume, so it’s 0
- so, ΔH = ΔE(sys) [ J or kJ ]
second law of thermodynamics
when 2 objects are in contact, heat is transferred from the hotter object to the cooler object until both objects have the same temperature
chemical systems
set of reactants and products being studies
surroundings
all matter around system that is capable of absorbing or releasing thermal energy
types of chemical systems
- open
- closed
- isolated
open system
- energy and matter can be exchanged with surroundings
- e.g. cup of water
closed system
- energy but not matter can be exchanged
- e.g. closed bottle of water
isolated system
- neither energy or matter can be exchanged with surroundings
- e.g. closed thermos of water
- there are no truly isolated systems
types of nuclear changes
- decay
- fusion
- fission
alpha decay
- atom (parent nucleus) gives off 2 protons and 2 neutrons
- mass decreases by 4
- atomic number decreases by 2
- He and energy always a product
beta particle
fast moving electron emitted from nucleus of atom undergoing radioactive decay
beta decay
- neutron changes into proton and electron
- nucleus has one less neutron and one more proton
- mass stays same
- atomic number increases by 1
- electron and energy in products
gamma decay
- gamma rays aren’t charged particles like alpha/beta particles
- they are electromagnetic radiation w/ high frequency
- excess energy emitted by unstable nuclei of new atoms formed by alpha/beta decay is called gamma rays
gamma ray photons have energies of
1 x 10^12 J
nuclear fusion
controlled process where two lighter atoms fused together and generate heavier atom and has aim of generating energy
nuclear fission
- process where heavy nuclide splits into two or more pieces
- release a lot of energy
