One word substitution

Feeling a guilt

• reparation

• remorse

• recuperation

• restoration

A christian mass in memory of a dead person

• requiem

• litany

• funeral

• obituary

Science which claims to turn base metals into gold

• Chemistry

• Archaelogy

• Alchemy

• Criminology

Something that is fit to be eaten

• edible

• menu

• fodder

• legible

Speech made without any preparation

• Debate

• Oration

• Elocution

• Impromptu

One who does not believe in God

• Rebel

• Iconoclast

• Atheist

• Savage

A quality of a metal of being beaten to any shape

• brittle

• malleable

• dense

• dirigible

Functioning by means of air

• aerobic

• inflationary

• vulcanizing

• pneumatic

Lasting for a very short time

• nascent

• transient

• embryonic

• lasting

Secretly listening to other's conversation

• overhearing

• spying

• eavesdropping

• pigeonholing