Why is 'water' considered a compound, while 'salt solution' is considered a mixture?

Water (H₂O) is considered a compound because: 

1. It is formed by the chemical combination of two elements, hydrogen and oxygen, in a fixed ratio of 2:1 by atoms. 

2. Its properties are entirely different from its constituent elements (hydrogen is combustible, oxygen supports combustion, but water extinguishes fire). 

3. It cannot be separated into its constituent elements by physical means; chemical methods like electrolysis are required. 

Salt solution (e.g., common salt in water) is considered a mixture because: 

1. It is formed by physically combining salt and water; there is no chemical reaction between them. 

2. The components (salt and water) retain their individual properties. Salt still tastes salty, and water is still a liquid. 

3. It can be separated into its components by physical means, such as evaporation (to get salt) and condensation (to get water).