A couple weeks ago my son was home sick from school and it was pouring rain outside so we took to the kitchen to do some science. I had serendipitously found a book at the library called, Kitchen Experiments the week before, and my son found it while he was home sick.
One of the experiments that we did was super simple and my two year old could do it easily. You need milk, food colors, toothpick, and liquid dish soap.
1. Get a shallow bowl or container and place about 1/4 inch of milk in it.
2. Put a few drops of food color spaced around on the milk.
3. Touch the tip of the toothpick into the dish soap .
4. Dip the tip of the toothpick into the milk in the center of one of the drops of food coloring (do not stir just touch it).
5. Watch the food coloring spread out.
6. Try doing it in different places around and watch how the colors mix.
7. Talk about what is happening, how the colors are moving quickly, swirling, and mixing. The soap is bipolar with one part being hydrophilic (water-loving) and the other part being hydrophobic (water-fearing). This means that one part (the hydrophilic part) dissolves in the water content of the milk, while the hydrophobic part of the soap attaches to the fat in the milk. This causes all kinds of movement in the milk. (Get a more complete explanation in the book or at this website).
8. This is a great way to see molecules in action! Of course most of this goes right over the kids heads at 2 and 5 but they really enjoyed seeing the colors moving and as they get older and we continue to do things like this they will get more adept at understanding all about what is going on to cause these reactions.
This activity is great for learning science, colors, action and reaction, vocabulary building. Overall the book has some great simple experiments with explanations about what is going on. My son was loving it!