 |
|
|
When you first saw the water, it was clear, right? Then you added a drop of red food coloring, which was a dark red. When it hit the water, the area right around where the drop hit turned red and then it quickly became pink as the drop seemed to spread out. Then the water in the whole glass stayed pretty clear. The same thing happened when you added the second drop. By the third drop (depending on how much water you had) the pinkish tone would last longer and cover a wider area.
So what is happening here? When you first start with the drop, it is in its concentrated form. That means that it is just food coloring, and it is not mixed with anything. Right now the water does not have any food coloring in it, either. When the food coloring was dropped into the water, it immediately began to spread out. Why? Because fluids and gases have the ability to flow. This means that the individual particles have the ability to move around and slide past one another. Solids can not do that. When the drop of food coloring was added to the water, the particles began moving away from each other. They did this becasue they try to become evenly distributed. Particles which are close together have a higher "energy of position" than do particles which are spread out. So they are moving to a lower position of energy. The water particles can also move and so they are trying to get into the area that the food coloring is in, since they want to be as spread out as far as they can possibly be, too.
When you added seven or eight drops, the water began to stay pink, didn't it?
This is because there are now enough of the red food coloring molecules to
be noticed among all of the water particles. Swirling the cup helps to speed up
the process by adding mechanical energy to the water, speeding up the movement
of both the water and the food coloring molecules.
| Let's go back for more experiments! | Go back to the diffusion experiment | Let's go back to the Introductory page |
 |
 |