This is another "where did it go?" activity:

Put one ounce of ink or liquid dye into a transparent quart container of water. Shake the container until the color is evenly distributed. How do you know that the particles of dye are still in the container?

Our eyes can see the color.

Now, mark the middle of the container with a piece of tape, and pour away half of the solution. Refill the container by adding clear water to it. Shake the jar and observe the color. Is it the same color? Why not?

There are not as many particles of dye in the water as there were before we diluted it.

Next, pour out half of the solution and refill the container with clear water. Each time you pour out the solution and refill the container with water, the amount of dye is cut in half.

See how many times you can pour out half of the solution, refill the container with clear water, and still see some color in the solution.

(Note: As the solution becomes lighter, it is easier to see any remaining color if you place the container on a piece of white paper and look at the solution from the top.)

You can also do this activity with other colored liquids, such as Easter egg dye, vegetable coloring, and iodine.

What we have to try to realize is that everything is made up of particles. Particles are made up of atoms. (This is, of course, over-simplification.) Atoms are so small that an ordinary drop of water contains more that 100 billion, billion atoms. (One hundred billion is 100,000,000,000 when written numerically. How many zeros would be in 100 times that much?) Atoms are so small that it would take all the people in the world all of their lifetimes, without taking time to eat or sleep, just to count the number of atoms in a pinhead.

So, when we think something is gone, it has been changed to another form (such as a solid having been dissolved in a liquid), and/or it has been reduced to such a tiny size, we can't detect it.