All molecular processes are governed by laws of thermodynamics and kinetics.
Thermodynamics refers to the energetics of a chemical reaction.
Thermodynamics provides a powerful framework within which the behaviour of biological
systems can be predicted. For example, whether a process will need heat.
First law of thermodynamics = Heat is a form of energy. Energy is always conserved – it
cannot be created or destroyed, only converted from one form into another! The sum of
energies of a system and its surroundings remains constant.
a real example of this is a dam or waterfall.
Stored energy kinetic energy mechanical energy electrical energy.
Note here that the total
sum of energy remains
constant. There is only
transferral of energy from
one form to another.
Energy is not being created
or destroyed.
, Energy changes during chemical reactions.
During a chemical reaction, the internal energy, U, may change. But the pressure, p, and/or
the volume V, may also change.
Energy derived from pressure and volume changes is given by E = p * V.
Energy forms.
Kinetic energy – the energy of a body or a system with respect to the motion of the body or
of the particles in the system.
- Kinetic energy is related to temperature.
Potential energy – the stored energy in an object or system because of its position or
configuration.
- Chemical bond energy is the energy stored in chemical bonds.
- Bond formation releases energy (exothermic reaction).
- Bond cleavage requires energy (endothermic reaction).
Endothermic and exothermic reactions.
Endothermic: energy absorbed from surroundings to break bonds.
Exothermic: energy released into the surroundings from bond formation.
This should not be confused with spontaneity!
Heat flowing into a system from its surroundings is defined as positive (+q)
A process that absorbs head from surroundings is endothermic
So the system gains heat, meaning the surrounding cool down.
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