You'll need a little girl (or boy, I suppose) who is celebrating her seventh birthday, and you'll want to invite five or so of your favourite five to seven year-olds.

Before your guests arrive, put out some white glue, a
Borax solution and some food
colouring. Set out a disposable cup and a cheap chopstick for each
guest. Pour some glue and a squirt of the food colour of choice
into each cup, then add a little Borax solution, stir, and
you'll get...

goo! Make sure you have a labelled airtight container for each
kid to take their goo home.

Next, take the party outside where you have set out vinegar, baking soda,
and a handy volcano
and rocket. Do the
volcano thing – everyone will want to poke at the "lava".

You might not be able to get the rocket to blast off. That's okay,
everyone will have fun...

Finish the outdoor explosions with the old Mentos and Diet
Coke trick.

Take a break from all the explosions to run and play.

Admire the cake which actually looks something like a volcano
this time.
Send everyone home with their goo, some Pop Rocks and a miniature version of the volcano, brew yourself a nice cup of tea and pat yourself on the back for throwing an awesome party. Contemplate how you're going to top this next year...