Jello consists of long molecules, like strings, of gelatin, in water. When water boils and is hot, the gelatin is pretty flexible and independent, and the solution looks like water and flows. As the temperature cools, the gelatin gets stiffer and interacts with its neighbors to form a tangled network, in which little pockets of water are trapped. The gelatin can get pretty stiff. If your definition of a mixture is something that you can separate and have each part retain its normal properties, and a solution is something that if you separate it, it looks different than its individual properties, then jello would be a solution.

I don't know exactly how you defined a mixture and solution in class. I just did a search on the internet and not all web sites agree on which substances are mixtures and which are solutions so I'll tell you what I think the difference is:a solution is a mixture of a liquid (like water) and some other substance. To be a solution though, the stuff mixed into the water has to evenly mix on its own. According to this, you might want to call Jello a solution because it is a mixture of a protein called collagen and water. But I would be a little careful about this. Let me tell you why. When you mix in the Jello powder with hot water you get gelatin. This gelatin is made of a protein called collagen, which is the same protein that makes up animal connective tissue. In this state it is a solution and the proteins are constantly getting kicked around by the motion of the water molecules and so get mixed up pretty well. As the water cools down, the collagen starts to combine (the technical word is "aggregate"). As it combines, it forms chains. Eventually, different chains combine into a big tangled mess which tends to lock the water in. You end up with a jiggly thing that acts almost like a solid but is very soft and easy to break up. That is what scientists call a "gel" and what most folks call Jello. It's still just a protein mixed in with water, but now the protein is organized, giving Jello different physical properties than it did when it was just gelatin. So I would call gelatin a solution. But I would call Jello a gel. They are different because they have different properties. Gelatin is a liquid but Jello is - well, it's not quite a solid but it's not really a liquid either. It's just a gel.

This is a very good question, and you are lucky to have a teacher who is VERY GOOD -- he told you that he does not know and the best answer is an honest one. The fact is that Jello is neither a mixture nor a solution. It belongs to a class of systems called colloidal dispersions (or sols) that have the properties of both mixtures and of solutions. Other examples of sols are milk, butter, ink and hair gel. Colloidal sols have particles that do not truly go into solution because they are big, but the particles are too small to precipitate on their own. So while sugar in water forms a solution, and sand and water form a mixture, jello and water (when properly heated and then cooled) form a sol.

Don't blame your teacher - there are lots of things that don't fall into the categories we learn in school. I think jello is a gel - a watery network of protein. I think jello melts if you set a container of jello in hot water. You could do an experiment to test it.

I did a Google search and found a web site which says that Jello is a colloid.