IB Chemistry Topic 5.1

Temperature (T)

average kinetic energy of all particles in an object

measured in Kelvin (K)

Heat (Q)

Thermal energy transferred from one object to another.

naturally flowing from hot objects to cold objects

measured in joules (J)

Enthalpy (H)

Internal energy of a particle

More commonly, we focus on energy change

measured in kJ/mol

Unless otherwise stated, all reactions occur at…

STP

100 kPa and 298 K

endothermic

energy transferred from surroundings to system

postive delta H

temperature of surroundings is reduced

products are higher in energy, less stable

exothermic

energy is transferred from reaction (system) to the surroundings.

negative delta H

increase in surrounding temperature

products lower in energy, more stable

What is the enthalpy of formation for any element in its standard state?

0

standard enthalpy change of formation

1 mole of a substance forms from its constituent elements

standard enthalpy change of combustion

1 mole of a substance completely burns in oxygen

standard enthalpy change of neutralization

1 mole of water is produced when an acid reacts with an alkali