Here's why:

* Ionic Compound: Sodium carbonate is an ionic compound formed by the electrostatic attraction between sodium ions (Na+) and carbonate ions (CO₃²⁻).

* Crystal Structure: These ions form a crystal lattice structure, giving it a solid form.

* Melting Point: Sodium carbonate has a melting point of 851°C (1564°F). This means it needs to be heated to a very high temperature to melt into a liquid.

While you can dissolve sodium carbonate in water to create a solution, the sodium carbonate itself isn't liquid in its pure form.