Here's why:

* Ionic Compound: Washing soda is an ionic compound, meaning it's composed of positively charged sodium ions (Na⁺) and negatively charged carbonate ions (CO₃²⁻).

* Polar Solvent: Water is a polar solvent, meaning it has a positive and negative end due to the uneven sharing of electrons.

* Attraction: The positive ends of water molecules are attracted to the negative carbonate ions, and the negative ends of water molecules are attracted to the positive sodium ions. This attraction overcomes the forces holding the ions together in the crystal lattice, causing the washing soda to dissolve.

However, the solubility of washing soda is temperature-dependent. It becomes more soluble as the temperature of the water increases.