In a glass of water, we lay sugar. If, you think that the water has become sweet, that is, it has changed, then this is not true. There was water in the glass, so it was. She has not changed in any way. But there was an additional substance, which as we know dissolved, evenly or not, was distributed throughout the volume of water. This formed a solution. It consists of water and sugar, but not sweet water, there is no such substance. In our perception it is sweet, but in fact it is two different substances.