It's important for scientists to know the properties of matter because all things are made up of matter. Each type of matter has different physical characteristics and scientists need to know and understand these characteristics to make calculations. For example, if a scientist would like to know the density of a certain type of matter, they would need to know the mass and the volume of that matter.
The main physical characteristics of matter are mass, volume, weight, density, odor, and color. These are the characteristics that help us to see matter, feel matter, and taste matter.
The main phases of matter are solid, liquid, and gas. Most matter is able to be all of these phases depending on their physical characteristics.
More importantly, scientists work with many different types of matter. It is important for them to know and understand the correct ways to handle and store types of matter. They also need to know if any types of matter will have a certain chemical reaction when mixed with other types of matter.
Good luck, hope this helps!