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The thermal decomposition of nitrates – ‘writing with fire’

Description

A message is written on filter paper with a solution of sodium nitrate and is then dried, rendering it invisible. Applying a glowing splint to the start of the message makes the treated paper smoulder and the message is revealed as the glow spreads its way through the treated paper.

Type of Activity

:
demonstration

Audience

:
Teacher

Age Group

:
11 to 16 years

Credits

:
This is an experiment from the Practical Chemistry project, developed by the Nuffield Foundation and the Royal Society of Chemistry.
the-thermal-decomposition...



Apparatus Chemicals

Eye protection

Filter or blotting paper sheets – as large as possible

Wooden splints

Hot-air blower, e.g. Hair dryer (Note 1)

Small paint brush

Beaker (100 cm3)

Stirring rod

Sodium nitrate(V) (OXIDISING, HARMFUL), about 10 g

Refer to Health & Safety and Technical notes section below for additional information.

 



 





Page last updated October 2015

A message is written on filter paper with a solution of sodium nitrate and is then dried, rendering it invisible. Applying a glowing splint to the start of the message makes the treated paper smoulder and the message is revealed as the glow spreads its way through the treated paper.

ADDITIONAL INFORMATION

This is a resource from the Practical Chemistry project, developed by the Nuffield Foundation and the Royal Society of Chemistry. This collection of over 200 practical activities demonstrates a wide range of chemical concepts and processes. Each activity contains comprehensive information for teachers and technicians, including full technical notes and step-by-step procedures. Practical Chemistry activities accompany Practical Physics and Practical Biology.

The experiment is also part of the Royal Society of Chemistry's Continuing Professional Development course: Chemistry for non-specialists