Biology 1.1

Structure of Water and Hydrogen Bonds

Chemical bonds

happen so that atoms can become more stable

Atoms need — outer electrons

8

Covalent bonds

nonmetal atoms sharing electrons (main nonmetals: CHONPS)

Ionic bonds

nonmetal and metal atoms sharing electrons (ex: NaCl)

Metal atoms do what in a bond?

Metal atoms lose electrons

Nonmetal atoms do what in a bond?

Nonmetal atoms tend to gain electrons

What are the two types of covalent bonds?

Nonpolar and polar

Nonpolar bond

When atoms share electrons equally (ex: C-H)

Polar bond

When atoms share electrons unequally

Why are polar bonds unequal sharing of electrons?

Difference in electronegativity

Electronegativity

atom’s attraction to electrons

Why is water a polar molecule?

Because oxygen and hydrogen atoms share electrons unequally. Oxygen (-) and hydrogen (+)

What is the bond WITHIN water molecules?

Polar covalent bond

What is the bond BETWEEN water molecules?

Hydrogen bond

Why do hydrogen bonds happen?

Slightly negative Oxygen attracted to slightly positive Hydrogens in other water molecules

What are the 5 properties of water?

Surface tension, Capillary action, High solvency, Ice less dense than water, and High specific heat

Surface tension

Water’s ability to resist the stretching of its surface- think: water bugs

Capillary action

Water’s ability to travel through thin tubes such as Xylem and Blood vessels due to COHESION and ADHESION

Cohesion

When water molecules form hydrogen bonds w/each other

Adhesion

When water molecules form hydrogen bonds w/other stuff

High Solvency (and use?)

Water’s ability to dissolve polar and ionic compounds- helpful for digestion and transport

Ice less dense than water (and use?)

Less heat in ice for hydrogen bonds to keep breaking and reforming, so the water molecules are stuck in perfect hexagon shapes, therefore it is less dense than moving molecules in water. Helpful for marine environments to insulate the water below the ice.

High specific heat (and use?)

Water’s ability to resist temperature change due to stability from large number of hydrogen bonds. Helpful to maintain stable aquatic environments

Specific heat

amount of energy required to change temperature of a substance.