 I have some water with me in this container and some sugar. So what I'll do is I'll take some sugar, I'll pour it, I'll pour it into this container and then start mixing the sugar in the water. So as I try and dissolve it, I wanted to think about when the sugar fully dissolves in the water, what kind of a change will that be? Will that be a physical change or a chemical change? So as you see sugar is completely dissolved, we can't see any more sugar in the container. The turns out this sugar is still sugar and the water is still water. But they have mixed together to form a solution. This change is physical because the sugar molecules have not changed. They have just dissolved evenly in the water. You can separate the sugar from the water if you try and boil this water. All the water will be boiled and all that will be left behind will be sugar. So dissolving sugar in water is really a physical change because you can get back the original sugar by physical means. For example, if you try and boil this solution. Now let's take some more sugar in the spoon and then let's try and heat it. What kind of a change do you think this is? Is this a physical change or a chemical change? Well, turns out burning sugar is an example of a chemical change. When sugar is heated to a high temperature, it breaks down into different substances. For example, carbon dioxide, water vapor and it changes its color and smell. This changes chemical because the sugar molecules have broken down into different molecules and it cannot be reversed by simple physical means like heating, warming or cooling. So once the sugar has been burnt, it is a new substance and cannot be turned back into the original sugar and therefore it's a chemical change.