Unit 1.1 Structure of Water and Hydrogen Bonding (All you need to know for AP EXAM)

What type of molecule is water?

Water (H₂O) is a polar molecule.

What causes the partial charges in water molecules?

Oxygen is highly electronegative, pulling electrons toward itself.

What are hydrogen bonds?

Attractions between the δ+ hydrogen of one water molecule and the δ− oxygen of another.

How does polarity affect water's interactions?

Water interacts well with other polar molecules but not with nonpolar ones.

What is cohesion in relation to water?

Water sticks to itself via hydrogen bonds, aiding in water transport in plants.

What is adhesion in relation to water?

Water sticks to other substances, especially polar surfaces, aiding capillary action.

What creates surface tension in water?

Cohesion at the surface of the water.

Why does water have a high specific heat?

Water resists temperature changes because energy must break hydrogen bonds first.

What is the significance of water's high heat of vaporization?

Water absorbs a lot of heat to change from liquid to gas, aiding in cooling through evaporation.

Why does ice float on water?

Water is less dense as a solid due to stable hydrogen bonds pushing molecules apart.

What is the universal solvent?

Water dissolves many substances, especially ionic and polar molecules.

What does hydrophilic mean?

Water-loving; polar or charged substances that dissolve in water.

What does hydrophobic mean?

Water-fearing; nonpolar substances that do not mix well with water.

How do hydrophilic and hydrophobic interactions affect biological structures?

They influence membrane structure and protein folding.

What is the dissociation of water?

Water can dissociate into H⁺ and OH⁻ ions.

What is the pH scale range?

The pH scale ranges from 0 to 14.

What is considered acidic on the pH scale?

A pH less than 7.

What is a buffer?

Molecules or systems that keep pH stable by absorbing or releasing H⁺ as needed.

How does water influence protein structure?

Hydrogen bonds stabilize secondary, tertiary, and quaternary structures.

How does water affect DNA structure?

Hydrogen bonds between base pairs hold DNA strands together.

What role does water play in cell membranes?

Hydrophobic tails of phospholipids avoid water, forming the bilayer structure.