IGG INVESTIGATE and EXPLORE Choice Challenges 22 (Invisible Ink)

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Description

Make a secret code and get another Brownie to crack it (Invisible Ink).

Resources

Lemon juice
A small bowl
A cotton bud or small clean paintbrush
Paper or a paper towel
A hair dryer

Instructions

Step 1:
Squeeze your lemon or
lemon juice into a small
bowl.
Step 2:
Use your cotton bud to write a message or draw a
picture on a piece of paper or paper towel using
your lemon juice as ink. Don’t use too much lemon
juice, or your paper will take a long time to dry.
Step 3:
Let your message dry until all the wet spots have
faded. Can you read your secret message?
Step 4:
Use your hairdryer to heat the paper. Move the
hairdryer back and forth over the paper so that it
does not burn; make sure you are using the warm
setting instead of the cool setting. After a few minutes,
you should see your secret message start to appear!
What happened?
The carbon compounds in lemon juice break
down and oxidize when exposed to heat and air.
What does that mean? Well, lemon juice contains
carbon compounds or mixtures of carbon and other
chemicals.
Without heat, those compounds are colourless
– that’s why you can’t read your secret message
after it dries. When those carbon compounds are
exposed to heat, they start to break down and
release carbon from the mixture. When that carbon
is exposed to the air around it or oxidized, it turns
brown, and your invisible message is revealed.

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IGG INVESTIGATE and EXPLORE Choice Challenges 22 (Invisible Ink)

Description

Resources

Instructions

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