Why does every sample of a given substance have the same properties

Subject : Chemistry

Question: Why does every sample of a given substance have the same properties?

Expert Verified Solution: 

Every sample of a given substance has the same properties because it is composed of the same type of particles (atoms, molecules, or ions) in the same proportions and structure.

Here are the reasons why:

Uniform Composition: A pure substance has a uniform composition, meaning it consists of only one type of atom or molecule. For example, every sample of pure water (H₂O) has the same composition of hydrogen and oxygen atoms in a 2:1 ratio.

Consistent Chemical Structure: In a given substance, the particles are arranged in a specific structure that determines its physical and chemical properties. This arrangement is consistent across all samples of the substance, so the properties remain the same. For instance, the crystalline structure of table salt (NaCl) ensures that every sample has the same melting point, solubility, and electrical conductivity.

Identical Chemical Bonds: The chemical bonds (ionic, covalent, metallic, etc.) that hold the atoms together in a substance are consistent in every sample of that substance. This consistency in bonding leads to uniform physical and chemical behavior across all samples.

Because of these reasons, every sample of a given substance will exhibit the same physical properties (such as melting point, boiling point, density) and chemical properties (such as reactivity, acidity, etc.).