Water and Salt (NaCl):
* Dissolution: When salt is added to water, it dissolves. This means the ionic bonds holding sodium (Na+) and chloride (Cl-) ions together in the salt crystal are broken. The water molecules, being polar, surround the ions and pull them apart.
* No Chemical Reaction: There is no chemical reaction between salt and water. The salt simply dissolves into its constituent ions, forming an electrolyte solution.
* Result: You get a homogeneous solution of salt dissolved in water. The solution is salty, but the chemical composition of the water and salt remain unchanged.
Water and Sodium Metal (Na):
* Violent Chemical Reaction: When sodium metal is added to water, a highly exothermic (heat-releasing) chemical reaction occurs.
* Formation of Sodium Hydroxide and Hydrogen Gas: Sodium reacts with water to produce sodium hydroxide (NaOH), a strong base, and hydrogen gas (H2). The reaction is represented by the following equation:
2Na(s) + 2H₂O(l) → 2NaOH(aq) + H₂(g)
* Heat and Explosion: The reaction is extremely rapid, generating significant heat and often leading to an explosion. The hydrogen gas produced is flammable and can ignite in the presence of air.
* Result: You get a solution of sodium hydroxide (lye) and hydrogen gas. The sodium metal is completely consumed in the reaction.
Key Differences:
* Chemical Reaction vs. Dissolution: Salt dissolves in water, while sodium reacts chemically with water.
* End Products: Mixing salt with water results in a solution of ions. Mixing sodium with water produces sodium hydroxide and hydrogen gas.
* Danger: Mixing sodium with water is extremely dangerous due to the violent reaction and potential for explosion. Mixing salt with water is generally safe.
In essence, salt dissolves in water, forming a solution of ions, while sodium reacts with water, producing new chemical compounds.
