* Pure Substance Definition: A pure substance has a fixed and definite composition. It cannot be broken down into simpler substances by physical means.
* Sodium Chloride's Composition: In sodium chloride, sodium (Na) and chlorine (Cl) atoms are chemically bonded together in a specific ratio of 1:1. This ratio is always the same, no matter where you find NaCl.
* Chemical Bonding: The bond between sodium and chlorine is a strong ionic bond, meaning the atoms are held together by electrostatic forces. This bond makes them act as a single, distinct substance, not just a mixture of sodium and chlorine.
Think of it like this:
* A mixture is like sand and sugar. You can see the individual grains of each. You can separate them easily.
* A pure substance like NaCl is like water. You can't see the hydrogen and oxygen atoms separately, and you can't easily separate them.
Therefore, even though it is made up of two elements, the consistent, fixed ratio and the chemical bond between them make sodium chloride a pure substance.
