Magic writing 
This activity has 2 parts and introduces you to some nifty science while practicing writing skills and having fun. You can even involve friends by sending them "secret messages"
Part 1:
You will need:
White paper
A lemon (or prepackaged lemon juice)
A saucer
Small paint brush or cotton tip
What to do:
Squeeze juice from the lemon.
Using the paint brush/cotton tip write a message or draw a picture on the paper dipping in the lemon juice "ink" frequently to keep the tip wet.
Leave to dry.
Send to a friend or relative.
Part 2:
You will need:
A message written in secret ink
A toaster* [*Parental supervision required]
What to do:
Warm up the toaster by running for a few minutes.
Hold the message over the toaster moving it around to warm the whole page.
Watch the message appear!!