UNIT 8

Temperature

The measure of the average kinetic energy of the particles in a substance.

Heat

The energy transferred between objects due to a temperature difference.

Specific Heat

The amount of heat required to raise the temperature of 1 gram of a substance by 1 degree Celsius.

Enthalpy Change

The heat content of a system at constant pressure, representing the energy absorbed or released during a reaction.

Thermochemical Equation

A chemical equation that includes the enthalpy change associated with the reaction.

Specific Heat Calculation

To calculate the specific heat of a substance using the formula: $c = \frac{q}{m imes riangle T}$ where $c$ is specific heat, $q$ is heat absorbed, $m$ is mass, and $riangle T$ is the change in temperature.

Enthalpy of Formation

The change in enthalpy when one mole of a compound is formed from its elements.

Enthalpy of Combustion

The change in enthalpy when one mole of a substance is burned in excess oxygen.

Entropy

A measure of the disorder or randomness in a system.

Free Energy Change (ΔG)

The change in free energy of a system, used to predict the spontaneity of a reaction.

Spontaneous Reaction

A reaction that proceeds without external intervention, usually associated with a negative free energy change (ΔG < 0).

Calculation of ΔG

Calculate free energy change using the formula: $riangle G = riangle H - T imes riangle S$ where $riangle H$ is enthalpy change, $T$ is temperature in Kelvin, and $riangle S$ is entropy change.

Processes Increasing Entropy

Processes such as melting, boiling, and dissolving that increase disorder in a system.

Processes Decreasing Entropy

Processes such as freezing and condensation that decrease disorder in a system.

Enthalpy of Formation Reaction for CaCO3

ext{Ca (s) + }rac{3}{2} ext{O}_2(g) + ext{C (s)}
ightarrow ext{CaCO}_3(s).

Enthalpy of Combustion for C6H12O6

ext{C}6 ext{H}{12} ext{O}_6 (s) + 6 ext{O}_2 (g)
ightarrow 6 ext{CO}_2 (g) + 6 ext{H}_2 ext{O} (l) + ext{heat}.