Ice & States of Matter
Understand ice in different forms and states of matter — sea ice forms when ocean water freezes (it's salty and relatively thin), glacial ice forms from compacted snow over centuries (fresh water, very thick), and icebergs break off from glaciers and float in the sea; know that water exists as solid (ice), liquid (water), and gas (water vapour), and that salt lowers the freezing point of water
What a learner can do afterwards
- Distinguish between sea ice (frozen ocean, salty, thin) and glacial ice (compacted snow, fresh water, thick)
- Explain that icebergs break off from glaciers and float because ice is less dense than liquid water
- Describe the three states of water (solid, liquid, gas) and explain that salt lowers the freezing point
The lesson
Water is not always the same. It can be a solid, a liquid, or a gas. Ice is water as a solid. The water you drink is a liquid. And water vapour, a gas you cannot see floating in the air, is water too.
Not all ice is the same. Sea ice forms when the top of the ocean freezes, so it is salty, and it is usually thin. Glacial ice is different: it forms when snow piles up and gets squeezed tight over hundreds of years, so it is fresh water, and it is very thick. When a big chunk of glacier cracks off, it becomes an iceberg, and it floats because ice is less dense than liquid water.
Salt gets in the way of water freezing. That is why salty ocean water has to get colder than fresh water before it turns to ice.
Water can be solid, liquid, or gas, and salt is why thin salty sea ice and thick fresh glacier ice, the source of floating icebergs, form so differently.
Watch it
Where it sits
Learn first
Where this leads
Jobs that lean on this skill. Follow one to see everything it is built on.
8 questions wait behind this lesson, each with its answer explained. Every answer feeds the sky: stars light as they are learned, and dim when it is time to come back.