How is water unusual for such a small molecule?

Answer 1

• Water is relatively light (MW 18).
• Highly polar, and thus an excellent solvent for many salts, ions, and other "polar" substances
• It is also a good solvent for Oxygen and Carbon Dioxide
• Its solid (ice) is of a lower density than its liquid (water), thus it floats. And, ice is also a relatively good insulator... put them together and the ice can protect water below from freezing.
• The oxygen-Hydrogen bond is relatively weak, and with the two unshared electron pairs on the oxygen, the water can essentially exist in 3 forms:
  • H3O+
  • H2O
  • HO- (or OH-)
  • Thus, it is both a good acid and a good base
• The Freezing Point (O°C) and the Boiling point (100°C) both lie near the average temperatures on earth, with water existing in solid, liquid, and gaseous forms on earth. Perhaps it also has a relatively high vapor pressure.
• Having a molecular weight lighter than Neon, Water would likely escape earth's atmosphere if it did not condense into water and ice in cold temperatures

Answer 2

Water has many unique properties. Two of the most important are that water is the only substance that has a lower density as a solid than as a liquid. Another important quality related to this is that water expands as it freezes.

Answer 3

Water is a compound because it is not a single element but made up of two different elements. Water is a single compound on its own. It often contains many others, and certainly some hydroxide. By the way what makes water an unusual compound is that without water we and plants and animals well die. The two main things that makes us alive is water and oxygen.

Water came from earth because earth has 77 percent water. Water that flows into our sinks and bathtubs either comes from rivers and lakes or from water flowing down below the Earth's surface called groundwater. Most towns and cities have a big system of pipes that go deep into the Earth, suck groundwater up from down below and pump it through a series of pipes all the way into our homes and schools.

You may be wondering how water gets under the ground. To understand where water comes from, we need to learn about a process called The Water Cycle.

Water in oceans, rivers, ponds and lakes is heated by the sun, which turns it into water vapor, (which is kind of like invisible water) and the vapor forms a cloud up in the sky. When a cloud gets so full of water that it can't hold anymore, it rains! The rain water travels back into our rivers and oceans, or it soaks down deep into the ground, creating more groundwater. It's a great system!