One way to know if a melted ice is a physical or chemical change is by seeing if the process is reversible. You can make the water that came from the ice cube frozen again. The water mixes with the freezing air but the substances don't change just the appearance.
This is a physical change because the paper is not being changed and the shredding process is reversible. When you shred the paper you can make it into new paper again. The page is only changing its size or appearance.
Boiling water is not a chemical change. The water is being heated but the molecules of the water vapor are the same as the liquid water. Therefore the molecules have not changed and its not a a chemical reaction.
Physical changes can also occur when you mix different things together. In order for this to work the components can not have any chemical changes. For example: Mixing salt and pepper does create a new substance but the chemical of either components are not changed.
Blending a smoothie includes two physical changes. One is the shape of the fruits. Second is the mixing. During the blending none of the components are being changed. They are all just changing the appearance. There is no chemical changes.