Question

Sponge though compressible is solid. Explain why?

Answer 1

Hint: The sponge is compressible being a solid because of the presence of air cavities inside the sponge. The sponge has numerous pores in it which can be referred to as air cavities, in which air is trapped and on compressing the sponge it comes out.

Complete step by step solution:
 -As we know sponge is a porous material. Even though they are originally made from natural sea sponges, nowadays they are generally made from synthetic materials.
-Synthetic sponges are made of polyurethane, polyester and vegetal cellulose. Vegetal cellulose sponges are considered more eco friendly than the other two since it is made from natural materials and biodegradable.
-As we are aware, the most well-known property of solid is that it has definite shape and mass. A sponge is a porous material with a system of cavities in it. If we look closely at the sponge, we can see that it has lots of holes in it. The pores in the sponges are the reason why it can easily soak liquid into it.
-Since there are holes in the sponge, air can get trapped inside these holes. When we compress the sponge, the trapped air inside the minute holes of the sponge gets expelled out.
 -The property of compressibility means that when an object is compressed and it remains in that compressed shape until we apply force to get it back to its normal position. When we compress the sponge, it can come back to its original shape in a minute or two.
-When we squeeze or compress the sponge, the solid part changes its shape but stays in the same size and the gas in the holes gets smaller, so the entire sponge takes up less space.
- As we have seen, a sponge regains its shape and mass remains the same after the compression.

Therefore, a sponge can be considered as solid though it is compressible.

Note: It must be noted that compressibility is the measure of how much of a given volume of matter reduces when placed under pressure. Generally, solids are considered incompressible because of the higher intermolecular attraction and closed packed nature. Sponge is an exception to these only because of its porous nature and air cavities.