Properties of Water

Accelerated BiologyDecember 2009

Nonpolar Molecules• Covalently bonded• Electrons equally shared• Atoms – similar size

Polar Molecules• Covalently bonded• Electrons not shared equally

• Atoms – unequal sizes• Charged ends ( + / - )

Hydrogen Bonds• Weak attractions between polar molecules.

• Attraction between + and – ends.

• Short-term (few trillionths of a sec).

• Break & reform constantly.

A Solution is…1. 2 Substances that combine

(solute & solvent)2. Will a combining 2 substances

form a solution?• Polar & Polar = solution (Salt & Water)• Nonpolar & Nonpolar = Solution (oil &

gasoline)• Polar & Nonpolar = Mixture, not a

solution (oil & water)

Both Polar & Nonpolar substances

Water (attractive forces at work)

• Cohesion–Water sticks (H-bonds) to other water molecules.

• Adhesion–Water sticks (H-bonds) to other molecules or substances other than water.

Surface tension

• cohesive forces between liquid molecules

• surface acts as a plastic sheet.

Additional Important Characteristics of water