Question

We have learnt that solids have fixed volume and negligible compressibility. So, how can we conclude that sponge is also a solid even though it has enough compressibility?

Answer 1

As per definition solids have a definite shape, liquids take shape of container and gases have no shape. If we leave sponge without any external force it always has the same definite shape, the shape changes due to external compression (as it has tiny pores when we press the sponge, the air inside the sponge comes out, and, when we release it, air will get into the sponge and it gets back its original shape). So sponge is called a solid.