Water, Water Everywhere
One hundred and forty-one million square miles (70%) of the Earth's surface is water; 55% of a person's body is water. However, of all the water on Earth, only about 1% is fresh water that is usable by humans.


  QUESTION 1: Water is a chemical made up of hydrogen (H) and oxygen (O).
What is the chemical formula for a single molecule of water?
HO         2HO         O2H         H2O

  QUESTION 2: Throughout Earth's history, water has been continuously recycled. This recycling relies upon two physical processes, evaporation and precipitation.
What do we normally call this precipitation?

  QUESTION 3: Rain comes from clouds. A cloud is simply an accumulation of water or ice particles suspended in the atmosphere.
Under what circumstances does water vapor in the air become concentrated into a cloud?
When the air temperature cools
when the relative humidity of the air increases
when the water vapor in the air condenses
when all of the above occur simultaneously

  QUESTION 4: In the formation of a rain drop, invisible water vapor in the air condenses to form tiny water particles. These are visible as clouds. Water particles in clouds continually bump into each other and join together into larger particles. When they are large enough (when about a million have joined together into each drop), they fall as rain.
What shape is a rain drop as it falls in a heavy rain from a cloud to the ground?
sort of doughnut shaped
somewhat pear shaped

  QUESTION 5: When water freezes into ice, the water molecules collect in groups.
How many molecules bond together to form each ice crystal?
3         6         9         12

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