Hidden Writing TELEGRAM TOP SECRET To STUDEN SECRET

Hidden Writing

TELEGRAM TOP SECRET To: STUDEN SECRET AGENTS From: SECRET AGENT HEADQUARTERS: OXFORD +++ MESSAGE RECEIVED FROM ONE OF OUR SECRET AGENTS +++HELP NEEDED TO DECODE MESSAGE +++REQUEST ASSISTANCE FROM STUDENT SECRET AGENTS+++ Not e from the We’ lab ve id : and e n t i mar ked fied fou rt them Each out ypes of for y invi you type is o u to re sible ink reve will veal righ a t ink need to led in a. use. d i the r fferen ight t meth way so od o n th e

Invisible ink 1 Starch is a molecule often found in food. Can you think of any foods containing starch? It is made of long chains of sugar molecules. Each sugar molecule is a ring and so starch is a lot of rings joined together in a long branching chain. Sugar Molecule Starch Molecule Iodine is a chemical element Iodine binds to starch and when it does, it goes black. Ink 1 is made out of starch – what will happen when we put iodine on it?

Invisible ink 2 A p. H indicator shows whether something is acid or alkali by changing colour under different conditions Phenolphthalein is a p. H indicator It is a compound that looks like this: When it is acidic it is colourless. When it is alkali it is pink. In the message, the indicator is colourless – what does this mean? How can we reveal it?

Invisible ink 3 Lemon Juice can be used as an invisible ink. It dries clear but when heated up it will discolour faster than the paper around it. Heat up the paper by getting one of the scientists to iron it under a hot iron. What happens? Can you think why? Invisible ink 4 Most ink shows up under normal light. Some ink however is invisible until the right sort of light is shone on it, at which point it shows up. This is a property called fluorescence. This is where it absorbs high frequency light (ultra violet light) And gives out (emits) lower frequency light (visible) and this allows us to see it. Where else have you heard of UV light? What sort of harm can it cause. Look at your message carefully and DO NOT shine the UV torch in your eyes.