Thermodynamics and Calorimetry - Key Terms

Vocabulary flashcards covering core thermodynamics and calorimetry concepts discussed in the lecture notes, including enthalpy, internal energy, PV work, calorimetry methods, and ideal gas relations.

Enthalpy (H)

A thermodynamic state function defined as H = U + PV; the heat content of a system, with ΔH representing heat added at constant pressure (under negligible non-PV work).

Internal energy (U)

The total energy contained in a system excluding PV-work; changes relate to heat and work via the first law.

PV work

Work associated with changing volume against pressure (W = ∫ P dV; for reversible processes, W ≈ PΔV for constant pressure).

Calorimetry

An experimental method to measure heat transfer by observing temperature changes in a calorimeter during a process.

Calorimeter constant (C_cal)

A factor that relates heat exchanged to the observed temperature change: q = C_cal × ΔT.

Constant pressure process (q_p)

A process at constant pressure where the heat added equals the enthalpy change: ΔH = q_p.

Constant volume process (q_v)

A process at constant volume where the heat added equals the internal energy change: ΔU = q_v.

DSC (Differential Scanning Calorimetry)

A controlled calorimetry technique that measures heat flow to a sample as it is heated/cooled, to study transitions.

Heat capacity at constant pressure (C_p)

The amount of heat required to raise the temperature by 1 K at constant pressure; related by ΔH = C_p × ΔT (for constant pressure processes).

Heat capacity at constant volume (C_v)

The amount of heat required to raise the temperature by 1 K at constant volume; related by ΔU = C_v × ΔT.

Ideal gas law (PV = nRT)

State equation for ideal gases: pressure times volume equals number of moles times the gas constant times temperature.

Enthalpy for an ideal gas (H = U + nRT)

For an ideal gas, enthalpy equals internal energy plus PV, which simplifies to H = U + nRT.

Cp − Cv = R (ideal gas relation)

For an ideal gas, the difference between heat capacities at constant pressure and constant volume equals the gas constant R.

ΔH vs ΔU for gas-phase reactions (ΔH = ΔU + Δ(n_gas)RT)

In reactions involving gases, the difference between enthalpy and internal energy changes arises from changes in the number of gas moles.