Crystals vs amorphous matter
Track 1 ended with a promise: crystals could be the next leap. Before we explain why, we need to be precise about what a crystal actually is — and what makes it different from regular silicon, glass, or plastic.
Key Concept
Crystal
A solid material whose atoms are arranged in an orderly, repeating, three-dimensional pattern that extends over very long distances (millions of atoms).
Key Concept
Amorphous
A solid where atoms have no long-range order — they're packed together but in a random arrangement. Glass, plastic, and rubber are amorphous.
Diagram · Build a lattice
interactive
Amorphous · random
reference
No repeating order. Electrons scatter constantly.
Build a lattice · drag atoms onto the grid
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Drop each atom on a grid cell to form the lattice.
Drag the loose atoms onto the green grid to convert a chaotic arrangement into a perfect crystal lattice.
Marbles on the floor vs oranges at the grocery store
Amorphous matter is like a jar of marbles dumped on the floor — atoms touching, but in chaos. Crystalline matter is like the perfectly stacked pyramid of oranges at the grocery store: every atom in a known position, every neighbor predictable.
Key Concept
Unit Cell
The smallest repeating box of atoms in a crystal. Stack identical unit cells in 3D and you reproduce the entire crystal — like a 3D wallpaper tile.
Key Concept
Lattice
The geometric pattern formed by repeating the unit cell through space. The lattice defines a crystal's symmetry, density, and many of its electrical properties.
Checkpoint · +5 XP
Which is amorphous, not crystalline?
Crystals you've already seen: diamond (carbon, cubic lattice), quartz (silicon dioxide, hexagonal), table salt (NaCl, cubic), and even snowflakes (water, hexagonal — that's why every snowflake has 6-fold symmetry). When something is described as a single crystal, it means the orderly pattern is unbroken across the whole piece.
Lesson Summary
- A crystal is a solid with atoms in an orderly, repeating pattern.
- Amorphous solids (like glass) have no long-range order.
- The unit cell is the smallest repeating block; the lattice is its repetition through space.
- Diamonds, quartz, salt, and snowflakes are all crystals you've seen.
Test Your Knowledge · +50 XP
1
What defines a crystal?
2
Which one is amorphous?
3
What is a unit cell?
4
Which is NOT a crystal?
5
Why do snowflakes have 6-fold symmetry?