Knowt 5 - Thermochemistry

Calorie (cal)

Unit of energy equal to the heat needed to raise 1 gram of water by 1°C, defined as 4.184 J

Nutritional calorie (Calorie)

Unit for food energy, equal to 1000 cal or 1 kcal

Chemical thermodynamics

Study of heat, work, and energy relationships in chemical and physical processes

First law of thermodynamics

Internal energy change equals heat added minus work done

Endothermic process

Reaction or change that absorbs heat from surroundings

Exothermic process

Reaction or change that releases heat to surroundings

Energy

Capacity to do work or supply heat

Heat (q)

Transfer of thermal energy between bodies

Internal energy (U)

Total energy within a substance or system

Joule (J)

SI unit of energy, equivalent to 1 kg m²/s² and 4.184 cal

Kinetic energy

Energy of motion

Potential energy

Energy that is stored

State function

Property depending only on current state, not path

Surroundings

All matter outside the system being studied

System

Portion of matter undergoing change

Temperature

Measure of hotness or coldness as average kinetic energy

Thermal energy

Kinetic energy from atom and molecule motion

Work (w)

Energy transfer via macroscopic changes like pressure or volume

Calorimetry

Process of quantifying heat in chemical or physical changes

Calorimeter

Tool measuring heat absorbed or released in processes

Heat capacity (C)

Extensive property for heat needed to raise temperature by 1°C.

Specific heat capacity (c)

Intensive property for heat needed to raise 1 gram by 1°C

Enthalpy (H)

Sum of internal energy and pressure-volume product

Enthalpy change (ΔH)

Heat released or absorbed at constant pressure

Hess’s law

Enthalpy change of a process equals sum of step changes

Standard enthalpy of combustion

Heat released per mole of compound burned under standard conditions

Standard enthalpy of formation

Enthalpy change forming 1 mole from elements in stable states

Standard state

Reference conditions of 1 bar pressure and 298.15 K for thermodynamic data

Thermochemistry

Study of heat in chemical reactions and changes

Heat Capacity Equation

C = q/∆T

Specific Heat Capacity Equation

c = q/m∆T

Heat Energy Equation

q = mc∆T = mc(T_f - T_i)

Internal Heat Energy Equation

∆U = q + w

Work of Chemistry Equation

-w = P∆V

Enthalpy-Change Equation

∆H = ∆U + P∆V

∆H = q

The Enthalpy Change of Reaction Equation

∆H°_reaction = ∑n x ∆H°_f (products) - ∆H°_f (reactants)