A pattern of particles
What is a crystal?
Salt and sugar grains
Look closely at rock salt, a sugar crystal for candy (mishri), or a snowflake. They often have flat faces and sharp, neat shapes.
What do you think is neat about them inside?
What this lesson covers
The idea
A crystal is a solid made up of particles arranged in a regular geometric pattern.
Salt and sugar grains
Look closely at rock salt, a sugar crystal for candy (mishri), or a snowflake. They often have flat faces and sharp, neat shapes.
What do you think is neat about them inside?
- Their particles are arranged in a regular pattern
- Their particles are scattered at random
- They have no particles
Zoom into two solids
Zoom in on solids P and Q. Which one is a crystal?
Crystal
A crystal is a solid that is made up of particles arranged in a regular geometric pattern.
Everyday crystals: rock salt, sugar crystals that grow while making candy sugar (mishri), snowflakes (water vapour freezing in the air) and frost on windows (water vapour turning into ice crystals).
Notes
A crystal is a solid made of particles in a regular geometric pattern. Salt, sugar candy (mishri) and snowflakes are crystals.
Check yourself
A crystal is a solid whose particles are…
You zoom in on a solid and see its particles in neat rows and columns that repeat. What is the solid?
How do snowflakes form?
- arranged in a regular geometric pattern — correct. Yes.
- jumbled with no pattern. That is not a crystal.
- free to move all around. That describes a gas.
- A gas. The particles of a gas move freely in all directions.
- A crystal — correct. Yes. A regular geometric pattern of particles makes a crystal.
- Not a solid at all. A crystal is a solid.
- Water vapour freezes in the air — correct. Yes. Snowflakes are crystals.
- Rain drops are boiled. Snowflakes form when vapour freezes.
- Sand sticks together in the sky. Snowflakes are ice crystals.