Thermochemistry

Thermochemistry

The study of energy changes associated with chemical reactions or physical transformations.

Endothermic Process

A system that absorbs energy from its surroundings; heat is on the reaction side and enthalpy (H) is positive.

Exothermic Process

A system that releases energy to its surroundings; heat is on the product side and enthalpy (H) is negative.

Heat

Energy that’s transferred due to a difference in temperature.

Thermochemical equations

Any equation with heat involved.

Enthalpy (H)

A form of chemical energy (potential energy) that cannot be measured directly but can be measured for changes during a reaction.

Heat Capacity

A measure of how well the substance stores/transfers energy.

Heat Capacity (C)

Amount of heat absorbed or released divided by the change in temperature.

Specific heat capacity (c)

Amount of heat required to raise the temperature of 1 gram of a pure substance by 1 °C.

Bomb Calorimeter

A device used to measure the enthalpy of combustion reactions.

Phase Change

A physical transformation of a substance, such as melting or boiling, which can be endothermic or exothermic.

H(f)

Heat of fusion; the amount of energy required to melt 1 gram of a solid at its melting point.

H(v)

Heat of vaporization; the amount of energy required to vaporize 1 gram of liquid at its boiling point.

q = mcΔT

The formula to calculate the amount of heat added or lost in a temperature change where q is heat, m is mass, c is specific heat capacity, and ΔT is the change in temperature.

q = mH(f)

The formula to calculate heat involved in a phase change (fusion) without a temperature change.

q = mH(v)

The formula to calculate heat involved in a phase change (vaporization) without a temperature change.