1.1 Water

The importance of water as universal solvent is to _________________________________

(the correct answer is more than 1)

• provide an aqueous medium for biochemical reaction

• act as medium of transportation in living organisms

• give evaporation cooling effect on leaves during transpiration

• act as a very effective temperature buffer for sudden temperature changes

Water molecules are polar, with the

• oxygen side being partially positive and hydrogen side being partially negative.

• oxygen and hydrogen sides being partially positive.

• oxygen and hydrogen sides being partially negative.

• oxygen side being partially negative and hydrogen side being partially positive.

Water is a universal solvent due to its

• cohesion of water molecules.

• polar molecules.

• high specific heat capacity.

• high latent heat vaporization.

Why does ice float in liquid water?

• The liquid water molecules have more kinetic energy and thus support the ice.

• The ionic bonds between the molecules in ice prevent the ice from sinking.

• Hydrogen bonds stabilize and keep the molecules of ice farther apart than the water molecules of liquid water.

• The crystalline lattice of ice causes it to be denser than liquid water.

The unique attractive forces that keep molecules of water together are called

• strong forces

• adhesion

• hydrogen bonds

• cohesion

Water striders can walk across the surface of calm water. Their feet push the surface of the water down slightly, but they do not break the surface. Why?

• The insects are light enough so they do not break the hydrogen bonds holding the water molecules together

• The insects actually use their wings to hover slightly above the water’s surface and they only skim it with their feet.

• The insect’s feet are non-polar, so they are repelled by the polar water molecules and are pushed away from the water’s surface.

• The insects are small enough to see the individual water molecules, so they are able to step carefully from one molecule to the next

What is a water molecule composed of?

• 1 hydrogen atom and 2 oxygen atoms

• 2 hydrogen atoms and 1 oxygen atom

• 2 oxygen atoms and 1 helium atom

• 2 helium atoms and 1 oxygen atom

Which property of water is responsible for cooling off the human body when sweat evaporates into water vapor?

• Surface Tension

• High latent heat of vaporization

• Ice floats on water

• Adhesion of water molecules

One water molecule can form hydrogen bond to a maximum of ............... water molecules.

• 4

• 3

• 2

• 1

The density of water is highest at 4ºC. What is the effect of this property of water?

• Water can act as a good solvent.

• Water can function as lubricant.

• Water provides cooling effect on animals.

• Water can function as an insulating layer.