Materials around us

Imagine you have two mysterious materials, X and Y. When
you try to press material X, it feels rigid and does not change
its shape easily. On the other hand, material Y easily changes
its shape when you press it. Now, when you mix both
materials in water, only material X dissolves completely while material Y remains unchanged. What can materials
X and Y be? Can you identify whether material X is hard or
soft? What about material Y? Justify your answer.