What are the benefit of understanding physical properties?

Physical properties help identifying a substance and how it changes.
For example: if a substance crushes easily that means it has a low density, but if it’s hard and doesn’t crush easily, that means it has a strong high density.
And eventually the substance would not end up forming a new substance.
Look at the picture below to understand more about physical changes.

I’m pretty sure it’s false i’m not sure

The density of water is 1 g/cm cubed and in order for the pebble to sink its density has to be greater than the density of water and in order for the twig to float its density has to be less than the density of water