Chemistry for Biology Students (CHEM0010) Notes - Thermodynamics
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Chemistry for Biology Students (CHEM0010)
Instelling
University College London (UCL)
Explore Chemistry for Biology Students with these specialized notes crafted for Year 1 students at University College London. Within this document, unravel the intricacies of thermodynamics, engaging with concepts such as energy, the first law, enthalpy, thermochemistry, entropy, and Gibbs energy. ...
C1: Energy and The First Law
Introduction to Thermodynamics
The Flow of Life
o Energy from the sun – photons
E = hν
E = energy of a photon
h = Planck’s constant
ν = photon frequency
Energy flow
Plants undergo photosynthesis = convert light energy to sugars
Plants are eaten by animals
Animals are eaten by other animals
Dead animals are broken down by bacteria
o Biological processes driven by light – light energy stored in ATP molecule
Hydrolysis of ATP – ATP > ADP + Pi + stored energy
Synthesis of cellular molecules
Synthesis of membranes
Cellular movements
Active transport
Generation of an electrical potential across a membrane
Heat
What is Energy?
Energy
o Energy – convertible currency of change in the universe
Energy is measurable and quantifiable
o Laws of thermodynamics
Law of conservation of energy – energy cannot be created or destroyed in an isolated
system
Entropy of any isolated system always increases
Entropy of a system approaches a constant value as the temperature approaches absolute
zero
First Law of thermodynamics
o Law of conservation of energy
Energy cannot be created or destroyed
The total energy of the universe is fixed
Energy can only be transformed from one kind to another
Energy is conserved
Measuring energy – heat capacity
o Convert energy into a temperature rise
Specific heat capacity
Energy (enthalpy) change in Joules required to raise the
temperature of 1kg of a material by 1°C (or K)
Specific latent heat (of fusion/melting)
Energy (enthalpy) change in Joules required to convert 1kg
of material from solid to liquid at the same temperature
Calorie
Energy required to raise 1g of water by 1°C
o Phase transition
Flat line: energy used to change state – not to increase temperature = phase transition
Calorimetry
, C1: Energy and The First Law
o Energy changes can be measured using a calorimeter
Calorimeter – insulated device in which temperature change associated with a specific
chemical or physical change can be measured
Used to measure the quantity of heat transferred to an object
Power and Metabolism
Measuring metabolism
o Metabolic rate – rate of energy conversion in Watts W or Joules per second J/s
P = dE/dt
P = power dispersed (W or J/s)
E = energy (Joules)
T = time (secs)
o Kleiber’s Law
Metabolic rate ≈ mass3/4
Distribution of Energy
Distribution of energy
o Types of energy in cells
Potential energy (stored energy)
Bond energy – chemical species
Chemical energy – concentration differences
Electrical energy – ion gradients
Kinetic energy
Thermal energy – motion of molecules
Radiant energy – photons
Electrical energy – ion flows
Maxwell-Boltzmann distribution
o Shows how the speeds of molecules are distributed for
an ideal gas
Distribution of speeds in a gas is
unsymmetrical – weighted towards lower
speeds
As the temperature rises – curve flattens +
moves to the right = more gas molecules move
at a higher speed
o Area under curve stays constant – number of molecules stays the same
o A system with energy levels
Most molecules are at lowest energy level
As temperature increases
Molecules move up into higher energy levels
Difference between lowest energy molecules
and higher energy molecules decreases
Lowest energy level = E0
Higher energy level = En
Temperature
o Temperature – reflects the distribution of thermal energy in a
system – described by the Boltzmann distribution function
A measure of the average energy in a system
E0 = lowest energy level
En = higher energy level
R = gas constant = 8.314 Jmol-1K-1
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