This is the list of my personal favorite chemistry demonstrations and activities. These are not necessarily kid-safe activities. They tend to include pretty colors and fire. However, if you're performing demonstrations for your own pleasure or to get kids interested in chemistry, these may be just what you seek.
1. Color Fire
Anne Helmenstine
Fire is fun. Colored fire is even better. These additives are safe. They won't, in general, produce a smoke that is any better or worse for you than normal smoke. Depending on what you add, the ashes will have a different elemental composition from a normal wood fire, but if you're burning trash or printed material, you have a similar end result. In my opinion, this is suitable for a home fire or kid's campfire, plus most chemicals are found around the house (even of non-chemists).
2. Classic Chemical Volcano
Anne Helmenstine
This is the old-school chemistry lab volcano, as opposed to the baking soda volcano that used to be a staple at science fairs. Ammonium dichromate glows and gives off sparks as it decomposes, and makes its own cinder cone of green ash. Chromium compounds are toxic - this is a chemistry lab demonstration and not a great choice for the armchair scientist. It's still cool. It involves fire. See a trend?
3. Borax Snowflake
Anne Helmenstine
This is a crystal-growing project that is safe and easy enough for kids. You can make shapes other than snowflakes, and you can color the crystals. As a side note, if you use these as Christmas decorations and store them, the borax is a natural insecticide and will help keep your long-term storage area pest-free. If they develop a white precipitant, you can lightly rinse them (don't dissolve too much crystal). Did I mention the snowflakes sparkle really nicely?
4. Liquid Nitrogen Ice Cream
Keith Weller, USDA
It's the quick way to make ice cream, plus, if you use your imagination, I'm sure you can come up with lots of other fun activities involving liquid nitrogen. It's easier to get and transport liquid nitrogen than you might think.
5. Oscillating Clock Reaction
George Doyle, Getty Images
There are many color-change chemistry reactions, pretty much using acid-base chemistry. I like this one because the colors oscillate (clear -> amber -> blue -> repeat). The blue bottle demonstration is similar, and there are other colors you can produce depending on the pH indicator you select.
6. Smoke Bomb
Timo Halén
It's cooking. It's chemistry. It's fun. This is another activity that's actually pretty safe, inexpensive, and easy.
7. Make Slime
Anne Helmenstine
You don't need to have esoteric chemicals and a lab to have a good time with chemistry. Yes, your average fourth grader can make slime. That doesn't mean it's any less fun when you're older.
8. Magic Rocks
Anne Helmenstine
This is the classic chemical garden or crystal garden, and one of the easiest ways to make an aquarium unfit for aquatic life ever again, so use a mason jar or other clear glass container that will serve no other purpose than to do this project. Metal salts react with sodium silicate to form fanciful waxy-looking towers.
