Thermodynamics

Thermodynamics

Gibbs free energy—free enthalpy: a measure of the energy freely available to use within the system.

- ΔG = H – TS

- Negative G: the reaction will proceed, favoured reaction.

- Positive G: unflavoured reaction.

- G = 0: neither the forward nor the backward reaction prevails, equilibrium.

Enthalpy: heat (work, energy) added to a system (internal or external).

- H.

- If a chemical reaction gives off heat, and warms up things around it, the enthalpy becomes less. The value of ∆H is negative. This kind of reaction is called exothermic.

- If a chemical reaction uses up heat, and cools down things around it, the enthalpy becomes more. The value of ∆H is positive. This kind of reaction is called endothermic.

Entropy: measure of disorganised energy in the system.

- Non-optimised energy; despite there being X energy units, only Y are accessible (X > Y).

- S—amount of energy “lost.”

There are four laws of thermodynamics that say how energy can be moved between two objects in the form of heat.

Zeroth law of thermodynamics

- If two systems have equal heat flow back and forth and one of the two systems has equal heat flow back and forth with another system, all three systems have equal heat flow with each other.

First law of thermodynamics

- An increase in energy in a system is the same as the energy given to a system in the form of heat.

Second law of thermodynamics

- Given a pair of systems touching with different temperatures, heat will flow from hot to cold until the temperature of the systems becomes equal.

Third law of thermodynamics

- When a system has a temperature of 0 kelvin, absolute zero (the lowest temperature), the entropy (energy that cannot be used to do work) is at 0.

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