The water comes in three physical states: Solid state (ice or snowflakes) Liquid state (liquid water) and finally Gas state (water vapor). Here is how to present the molecules in three states:
Solid state (ice)
Molecules in contact, vibrating in a fixed position (regular lattice)
Liquid (water)
Molecules in touch, vibrant and mobile
Gaseous state (water vapor)
Molecules remote, intensely vibrant and fast-moving, bumpers possible
Illustrations from the Canadian Museum of Nature
Most liquids contract if the temperature drops. Water is different. Water contracts to 4 o C, then it expands until it solidifies. Ice is less dense that liquid water, because the ordered state leaves gaps that are filled in the disordered state. If water behaved like other liquids, then there would be no iceberg, ice would sink in your lemonade glass, and ponds would freeze from the bottom! On earth water behaves between these forms. This is why the earth is a very special planet with just the appropriate temperatures and pressures.
The water molecules attract each other. This is called cohesion . Other materials may also attract water molecules This is called adhesion.
The surface tension is the name we give to the cohesion of surface water molecules. Place a drop of water on a piece of waxed paper. Examine the drop. What shape is it? Why has it that form? What is happening? The water molecules are not attracted by the waxed paper. Each molecule of the droplet is attracted to the other molecules of the drop. This explains why water minimizes its surface and tends to a spherical form. It is as if the molecules of the surface formed a "skin" that holds the other molecules: The surface tension
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Gently place a clip on the water. What is happening? It floats. The following animation shows the efect of surface tension:
Surface tension comes from the cohesive properties of water. Capillarity, on the other side, comes from its adhesive properties. Place a transparent straw in a glass of water. Check the water level in the straw: Water rises in the straw.
→ 1. Evaporation → 2. Transpiration → 3. Condensation → 4. Precipitation 5. Runoff 6. Percolation 7. Underground water 8. River transport
Evaporation : Heated in the sun, the molecules of surface water store enough energy to get free from attraction that binds them together, and then they evaporate and rise in the atmosphere as invisible vapour
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Transpiration Plant leaves also give off water vapor by the transpiration phenomenon. Growing plant los each day 5 to 10 times the amount of water it can hold
.Condensation : During his rise in the atmosphere, water vapor cools and condenses around tiny particles of dust in the atmosphere. As it condenses it becomes liquid or passes directly to solid state (ice, hail or snow). The water particles assemble to form clouds.
Precipitation : Precipitation in the form of rain, snow and hail from the clouds. They revolve around the earth through the action of air currents. For example, when they rise above mountain chains, they are cooling further and are so saturated with water droplets that they begin to fall as rain, or hail or snow according to the temperature of the ambient air.