Intro to thermochemistry

Thermochemistry

The study of the energy changes occuring during chemical reactions and phase changes

1 law of thermodynamics

Energy can either be created, nor destroyed. Energy can only be transferred or changed to different forms

2 law of thermodynamics

Entropy of an isolated system always increases. Isolated systems spontaneously evolved towards thermal equilibrium.

Entropy

The measure of randomness or disorder

Potential

Energy possessed by something due to the position

Chemical potential

Energy stored in or between molecule bonds

Kinetic

Energy due to motion

Heat

Transfers of energy due to temperature differences, represented by q

Open system

Mass and energy can be exchanged

Closed system

Only energy can be exchanged

Isolated system

No exchange of mass or energy

Endothermic

• Absorbs heat from surroundings

• System gains heat

• surroundings cool down

• Heat into system = +q

• EX: Coolpack

Exothermic

• Releases heat into surroundings

• System looses heat

• Surroundings heat up

• Heat out of system= -q

• EX: Hotpack

Enthalpy

A thermodynamic property representing the total heat content of a system, defined as the sum of its internal energy

𝐇 = 𝐔 + 𝐏𝐕

h = enthalpy

u = sum of internal energy

p = product of pressure

v = volume

Endothermic bonds

Bonds are stronger in the reactants than products

Exothermic bonds

Bonds are stronger in the products than reactants