Physical Properties
Physical properties are characteristics of a substance that can be observed or measured without changing the composition of the substance. Some common physical properties include physical state, density, and size of constituents.

Physical State
- Physical state refers to whether a substance is a solid, liquid, or gas at a given temperature and pressure.
- Solids have a definite shape and volume, liquids have a definite volume but take the shape of their container, and gases have neither a definite shape nor volume.
- For example, ice is a solid at room temperature, water is a liquid, and steam is a gas.

Density
- Density is a measure of how much mass is contained in a given volume of a substance.
- It is calculated by dividing the mass of an object by its volume.
- Different substances have different densities, which is why some objects float in water while others sink.
- For example, iron is denser than wood, which is why iron sinks in water while wood floats.

Size of Constituents
- The size of constituents refers to the size of the particles that make up a substance.
- Substances can be made up of atoms, molecules, or ions, depending on their composition.
- The size of these constituents can affect the physical properties of the substance, such as its melting and boiling points.
- For example, substances made up of small molecules tend to have lower melting and boiling points compared to substances made up of larger molecules.
In conclusion, physical properties such as physical state, density, and size of constituents are important characteristics that help us identify and classify different substances based on their observable and measurable traits.