AP Bio Unit 1 Module 2

What bond is hydrogen and oxygen joined by?

Polar covalent bonds

What does a polar covalent bond do for hydrogen and oxygen?

Holds the atoms together

What are polar covalent bonds characterized by?

Uneven distribution of electrons

Why are the bonds of water polar?

Oxygen is much more electronegative than hydrogen as a result the shared electrons are likely to be near the O atom than H atoms creating regions of slightly negative and positive charges

Polar molecule

A molecule that has regions of positive and negative charge (ex. water)

What does polar nature give to water?

It’s unique properties

Hydrogen bond

An interaction between a hydrogen atom with a slight positive charge and an electronegative atom of another molecule

When does a hydrogen bond form?

Between two water molecules when the partial positive charge of an atom charge is attracted to the partial negative charge of an oxygen atom

What is a hydrogen bond depicted by?

A dotted line

Hydrogen bonds are weaker than what bonds?

Covalent and ionic

What is waters 3 unique properties?

Cohesion, adhesion, surface tension

Cohesion

Water molecules tend to stick together

What unique property of water drives the formation of drops, puddles, streams, rivers, lakes and oceans?

Cohesion

Which of waters unique property contributes to water movement in plants?

Cohesion

Adhesion

The tendency of water to stick to other materials other than water

High surface tension

A measure of difficulty of breaking the surface of a liquid

What is a consequence of cohesion?

High surface tension

One of the highest surface tension of common liquids

Water

What causes surface molecules to stick to other surface molecules more strongly?

Surface molecules do not have other molecules surrounding them on both sides

Hydrogen accounts for what different structures of water?

Solid, gas, liquid

What structure of water is this?

Ice

What structure of water is this?

Liquid

What structure of water is this?

Gaseous

In ice water structure what happens to the water molecules?

Each water molecule is hydrogen bonded to four other water molecules

In liquid water structure what happens to the water molecules?

Water molecules move around so hydrogen bonds continuously form and break apart and water molecules are closer together than ice making liquid water more dense than ice

In Gas water structure what happens to the water molecules?

Water molecules move around even more rapidly keeping the water molecules further apart and preventing most hydrogen bonds from forming

What causes water’s great stability?

The large number of hydrogen bonds

What is a consequence of water’s great stability

Changing water from liquid to a gas requires more energy input than other substances

Molecules are in constant motion, what happens when this motion increases

The temperature increases

What happens when water is heated?

Added energy is used to break apart hydrogen bond, that energy cannot be used to cause motion in the molecules so that temperature increases less than it would if hydrogen bonds were not present