Thermochemistry Vocab

Thermochemistry

The study of heat changes that occur during chemical reactions & physical changes of state

Energy

The ability to do work or supply heat

Kinetic Energy

Energy of motion

Potential Energy (PE)

Stored energy (chemical bonds)

Heat

(q) a form of energy associated w/ the motion of particles

* Heat flows from warmer objects to cooler objects

Thermal Equilibrium

If two objects come into contact w/ one another, heat will move from the warmer object to the cooler object until they are the same temp.

* At this point, thermal equilibrium is reached

Temperature

A measure of heat; increase heat, increase temp

Chemical Potential Energy

Stored energy in chemical bonds

* Depends on the type of atoms and arrangement

Chemical reactions are described as being either…

Exothermic or endothermic

Exothermic

PE is converted to heat (heat is given off - feels hot)

Endothermic

Heat is absorbed and converted to PE (feels cool)

Law of Conservation of Energy

Energy can neither be created nor destroyed, only converted from one form to another

Units of energy

* Joule (J) (KJ=1000J)
* calorie (cal): chem. calorie
* Calorie (Cal): food calorie (kcal)
* 1 food Cal=1000 chem cal
* 1 cal=4.184J

Temperature

A measure of heat; increase heat, increase temp.

Calorimetry

Is the accurate and precise measurement of heat change for chemical and physical processes

Calorimeter

Is a device used to measure the amount of heat absorbed or released during these processes

Specific heat (c)

Amount of heat required to raise the temp. of 1 gram of a substance by 1 degree Celsius

Delta T

Change in temp. (Degree(s) celsius) (T-final - T-initial)

Enthalpy (delta H) (heat of reaction)

(H) heat content of a substance at constant pressure. This is the “Heat of a reaction” - heat absorbed or released during the chemical reaction. Delta H = change in enthalpy

Thermochemical equation

A chemical equation which includes the energy used or produced during the chemical reaction. Every reaction has an energy change associated

Heating curve

Graph of temp. versus time. Describes the enthalpy changes that take place during phase changes

Heat of fusion (delta H(fus)

the amount of energy required to melt a substance (solid →liquid)

Heat of vaporization (delta H(vap)

the amount of energy required to vaporize (boil) a substance (liquid →gas)