I have 1, 3, and 4 year olds. The best directly STEM-related activity we've done so far is a soap making "science experiment" kit. The 3 and 4 year olds absolutely loved it.
It was super simple. The kit comes with soap cubes, dyes, fragrances, and glitter. You follow the instructions to melt the cubes, add the dyes and fragrances, pour them into a mold, then let it set. Then you've got a bar of soap.
I was surprised at just how many useful things they got out of it:
- Basic lab safety: Wearing gloves, goggles (if you have a set that fit), wafting to smell the fragrances, staying away from a heat source (the stove), etc.
- Basic mechanical skills and techniques: using a scale to measure the ingredients, using using a butter knife to cut the soap, double boiling, using graduated pipettes to measure the colors and fragrances
- Understanding of colors: The kit comes with a chart about how to mix the dyes to get different colors. The kids got excited to try out different combinations. If you have a mixing palette they can try out different things.
- Phase transitions and heat: You can explain how heat and phase transitions work when the soap melts. Plus they love to watch it melt (safely, using goggles and staying away from the heat). I encouraged them try different things to make the soap bars solidify faster - a small electric fan, putting it in the freezer (very carefully), etc.
All told it was super rewarding for me and they really enjoyed and got excited by it. They are still using the soap bars and asking to do it again weeks later. I'm sure my little discussions about things like heat and phase transitions won't stick, but I'm hoping if we do it a few times having the terms and techniques bouncing around in their heads may help them a bit in the future.
The 4 year old got the most out of it, but the 3 year old was right there with her in the mix. The 3 year old couldn't handle things like reading the scale and pipettes, but I felt like she still got a lot out of it.
Other recommendations:
- Marble games and legos. Get sets with directions and encourage them to follow the directions. My 4 year old can now build pretty complex marble games and lego sets by carefully following the directions. She started when she was about 3.5 yrs old. Personally I think they get more out of the small legos (not duplos) once they hit about 3 and aren't going to just eat them.
- I agree with the magnet tiles, those are nice.
- They never seem to get much out of puzzles. They require too much self-direction, it's too easy to fail, and they just don't hold their interest. Maybe when they are older.
- Hydroponics kits like AeroGarden. Make them do all the work (plug it in, add water, add plant food, add seed pods). Explain what's going on. My 3-4 yr olds got very excited to watch the plants grow day-by-day and enjoyed adding water/plant food when needed. I would use an aerogarden type thing because at this age failure = no interest, and you basically can't screw up an aerogarden absent adding too much plant food.