Because they were made to be solid
The density of water in its solid state, which is ice, is lower than that of most other solid materials. This is why ice floats on water.
Superfluidity
This is a mixture of materials which can be distinguished from each other.
Materials that can exist in both solid and liquid states are primarily classified as phase-change materials, such as water (ice and liquid water) and certain metals like gallium and mercury. These materials undergo phase transitions based on temperature changes, allowing them to coexist in multiple states. Additionally, some polymers can exhibit both solid and liquid behaviors depending on temperature and pressure conditions.
glass and other solid like materials
ice
Seismic waves travel through the Earth's interior, primarily through solid rock. They can also travel through other mediums such as magma and other materials found in the Earth's crust and mantle. The speed and direction of seismic waves change as they encounter different materials with varying densities and properties.
The other materials other than just silicon used to make semiconductors and other solid state electronic devices are germanium and gallium arsenide.
Solid, liquid, gas are classical states of matter.
In India, there are standards for both hollow and solid concrete blocks. Standards include types of cement to be used and other materials added to the materials.
if you're talking about states of matter it is solid, liquid, and gas
I think it's the other way 'round. I think materials that are rigid and hard are called solid.