More Changes of State
- surface water evaporates and snow & ice sublime from the Earth's surface
- water vapour in the Earth's atmosphere acts like a blanket that traps thermal energy close to Earth
- once water vapour is in the atmosphere, the low temperatures cause it to condense or undergo deposition to form ice crystals and these form clouds and air currents move the clouds around
- these droplets eventually form rain or snowflakes that eventually fall onto the ground (precipitation)
- fallen snow may eventually accumulate as polar ice sheets, icecaps (not the coffee :) ), or glaciers
- At low temperatures, Earth's surface water freezes and forms ice which is less dense than water so it stays on top of liquid water allowing plants and animals to survive in winter
Check Your Learning
1. Describe the water cycle. Draw a labeled diagram.
2. Briefly describe how solid and liquid water may be converted into water vapour.
3. Describe how water vapour changes into solid and liquid water above the Earth's surface.
4. Does all surface runoff move directly into rivers, lakes, and oceans? Explain.
Changes of State in the Water Cycle
- water moves around Earth in the water cycle
- water exists in its 3 states through the water cycle
- solid water exists in permanent ice and snow (glaciers), and ice and snow in the winter season
- Liquid water forms when solid water melts in the spring and summer months, much of this water is called runoff water
- all water on the Earth's surface is called surface water
- some liquid water seeps into the ground, it is called groundwater
- groundwater flows underground filling up spaces until it fully saturates the soil and rocky areas which are called aquifers
- the top surface of the aquifer is called a water table
Changes of State
- when water changes state, the total number of particles remain the same
- there are 6 changes of state:
- melting -when ice gains thermal energy it changes state from solid to liquid
- sublimation -change of state from solid to gas by the addition of thermal energy
- evaporation -when water absorbs thermal energy it changes from liquid to gas
- condensation -when there is a loss of thermal energy water changes from gas to liquid
- deposition -when water vapor looses thermal energy it can sometimes from gas to a solid
- freezing -when liquid water looses thermal energy it freezes and becomes a solid
This idea is reinforced in this video
A Review of the Basics
- water is the only substance on Earth that exists naturally in each of its 3 states
- water sometimes changes its location by changing state through the water cycle
- the water cycle is self-renewing and constant
- the Sun provides the energy to power the water cycle
The Water Cycle
A Review