Ice Crystals in a Cold Cloud

In the picture

1. 1Dust speck: a tiny solid particle where an ice crystal begins.
2. 2Broad plate crystal: a flat six-sided ice crystal.
3. 3Six-armed star crystal: a branched ice crystal with six arms.
4. 4Slender column crystal: a narrow six-sided ice column.
5. 5Drifting water vapor: invisible water molecules moving through the cold cloud air.

Examples

• Frost on a car window
• Snowflakes landing on a dark coat sleeve

Quiz: Ice Crystals in a Cold Cloud (Age 15)

1. 1

   How do snow crystals begin to form inside cold clouds?

   • Tiny dust specks melt and then turn into ice.
   • Water vapor freezes directly onto tiny dust specks.
   • Liquid raindrops freeze together into a solid mass.
2. 2

   What decides whether an ice crystal grows into a plate, a star, or a column?

   • The temperature and humidity around it.
   • The number of dust specks nearby.
   • The speed of the wind through the cloud.
3. 3

   What is a dust speck in the formation of an ice crystal?

   • A tiny solid particle where an ice crystal begins.
   • A narrow six-sided ice column.
   • An invisible water molecule drifting in cold air.

The answers, each with its explanation, are in the app. This lesson has left the free week, so its quiz is part of the subscription.