The solid state
Solids in the Universe Solids on Earth What makes a solid? Physical types of solids

Click for larger imageOf the four states of matter, solids are probably the most familiar to us and the easiest to understand and describe. We build solid structures, surround ourselves with solid objects and value the solid state because it is unchanging and predictable.

Solids in the Universe
Solids are the third most common state in the Universe, in the form of cosmic dust, Earth-like planets, comets and other stray pieces of rock. To form solids, the matter involved must have fairly large, heavy particles.

The known Universe is 99% hydrogen and most of the rest is helium. These are the two lightest elements. Relatively very few heavy atoms and molecules have been formed since the beginning of time, some 12 -15 billion years ago.

Solids on Earth
Most of the outer layer of our Earth is solid. This solid mantle sits on a liquid outer core which surrounds an inner solid core. Two thirds of the Earth's surface is covered in liquid water. By mass, solids are the second most common state, behind liquids.

What makes a solid?
Solids are typified by an unchanging shape and by the fact that they occupy a set volume. Substances which are solids under normal conditions (25°C and 1 atmosphere pressure) are usually made of large heavy atoms or molecules and are tightly bonded together. Although the particles in a solid may vibrate and spin with kinetic energy, they cannot break free of the strong bonds holding the particles together in a lattice structure.

Particles in a solid.

Physical types of solids
Pure substances that are solids generally fall into one of two categories: crystals or glasses. Crystals, typically, have well defined lattice structures, while glasses have a disrupted structure. They are sometimes likened to a "suspended liquid", that is, having the chaos of a liquid, but the rigidity of a solid.

Complex solids such as wood, paper, rocks, plastics and foams are made up of mixtures of different substances forming a overall solid. Within this solid structure there can be liquids and gases as well as solids.

Particles in glass.

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  FAQ:
  Is glass a solid or really a liquid?
What about silly putty?
 
 
Related
Topics: 
  States of matter
The liquid state
The gas state
The three states of water - "the water cycle"
Changes in state
Changes in state - melting and freezing
Changes in state - boiling, evaporation and condensation
 
 
Quiz:
  Question 1
Question 2
Question 3
Question 4
 
 
Sites:
  Solids at Chem4Kids
CHEMystery:Solids
 
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