[always with adult attendance - Ed.]

As a younger child, my son LOVED mixing baking soda and vinegar in
zip lock bags and watching the bags fill with CO2. We then 'poured'
the CO2 into a plastic pail and lowered a lit match into it (by hand).
The match goes out when it passes into the CO2. But if you can get a
strip of magnesium, ignite that and lower that into CO2 - it won't
go out but will instead strip the oxygen off the CO2, leaving carbon
dust floating in the pail. It is also good because its sparks brightly
and makes loud popping noises. Be using magnesium - perhaps
do it outside

Get a stalk of celery and cut it lengthwise about 2/3 of the way up.
Get two drinking glasses and fill with water. Place them side by side.
Add two different colors of food coloring into the glasses, i.e. red
in one and blue in the other. Place the celery such that
one part is in one glass and the other part is in the other (which is
why you cut it 2/3 of the way.)
Come back the next day and look at the stalks.

Get an ordinary egg and put in a glass. Pour in vinegar sufficient to
cover it with perhaps 1" to spare. Let sit overnight. The next day take
out the egg and feel it....the vinegar has dissolved the calcium carbonate
in the shell and the shell is gone. You are feeling the membrane that
lined the shell and it has a rubbery feel. Rinse with plenty of water.

Get calcium carbonate (blackboard chalk is perfect). Heat up real hot in
a propane blowtorch (put the chalk in a vise). This will drive the
CO2 out of the CaCO3. This leaves CaO (lime). When you heat up lime, it
gets bright - which is where the word LIMELIGHT comes from. Drop in water
when done.

Go to radio shack and buy magnets of all types (square, circular, etc).
Give them to you child, along with paper clips, bobby pins, iron nails, etc
You child will have a ball with it.

Then get wire at radio shack and wrap many many turns around an iron nail.
Connect that to a battery and you have an electromagnet. Show your child
how it also picks up paper clips, etc.

Go a hardware store and get root killer. Look at the package - it should be
copper sulfate pentahydrate. When you open it up, it will be blue crystals.
This is good stuff to work with but be careful - poisonous - wash your hands
after touching it. Anyway, drop some in a glass and dissolve in water.
Then get an iron nail and sandpaper it a bit to make it shiny. Drop it in
and wait a few hours. It will get copper-plated. (Has to do with the
relative activity of metals)

Now dissolve more in water- this time to excess, i.e. have crystals sitting
on the bottom. Connect an old spoon to a wire and connect that wire to
the negative pole of a DC powersupply. Connect some copper wire to the
positive pole of the DC powersupply. The other end of that copper wire should
be stripped clean and dropped in the water. Don't let the two touch while
in the water. After a while, the copper wire in the water will start to
shrink in size but the spool will get a copper coating. (Copper plated).
The DC power supply can be batteries but use at least 3 volts or so.

Get a small piece of aluminum foil, about 4" square. Fold it in 1/2 two
times and this will give you 1" square. Get some lye from the grocery store
or hardware store (Caution - corrosive, dangerous stuff). Get a 3-4 crystals
of lye and place on the foil, dead center. Place the foil on a paper plate
and plate this in a sink. Add 1 drop of water to the crystals and step back.
The water will dissolve the lye. The lye is now in solution and in
contact with the aluminum foil. The aluminum foil is covered with a
thin layer of aluminum oxide (invisible). The lye solution starts to react
with the aluminum oxide and breaks it down. It then hits the foil and
reacts with that. As the reaction gets going, it heats up. This causes the
reactants to mix it up even faster and get even hotter. Finally, you run out
of either lye or aluminum.
Rinse thoroughly with water when done. Moral - never mix lye with aluminum.

A slow burn - get plain old steel wool (non-detergent) and plain old
strong clorox (again - non-detergent). Place the steel wool in a large
bowl or glass. Pour the clorox over it, covering it. Let sit overnight.
Come back tomorrow and most of the steel wool is gone and you now
have plain old rust. (P.S. this will make the clorox quite warm - let it
sit in a sink overnight in case it breaks - don't squeeze the steel
wool before you use it. Just put in as-is - if you squeeze it or
stretch it, the reaction will go faster and become hotter).
Rinse thoroughly  with water when done.

Keep the chemicals away from your child - potent stuff.
Don't mix chemicals on your own without knowing what you are doing.
Some household chemicals and combinations thereof are EXTREMELY dangerous.

Have fun and hope that helps....

Mail me if you want more experiments or have questions on the above.