BIO101 Unit 1 Chapter 3

Why is water a polar molecule?

Oxygen is more electronegative, pulling electrons toward itself and giving O a partial negative charge and H atoms partial positive charges.

Which atom in water carries the partial negative charge?

Oxygen

What causes hydrogen bonding between water molecules?

Attraction between the partial negative oxygen of one molecule and partial positive hydrogen of another.

What is cohesion?

Hydrogen bonds hold water molecules together.

How does cohesion help plants?

It pulls water upward through xylem in plant stems.

What is adhesion?

Water sticks to other surfaces (like plant cell walls).

What is surface tension?

The difficulty of breaking a liquid’s surface; water has high surface tension.

What allows water to stabilize temperature?

Its high specific heat due to hydrogen bonding.

What is heat?

Total kinetic energy of molecules.

What is temperature?

Average kinetic energy of molecules.

Why does water resist temperature change?

Heat must first break hydrogen bonds before temperature can rise.

What is evaporative cooling?

Surface cools as high-energy molecules evaporate.

Why is ice less dense than liquid water?

Hydrogen bonds form a crystalline structure that spaces molecules farther apart.

Why is floating ice important?

It insulates liquid water, protecting aquatic life in winter.

Why is water called the “universal solvent”?

Its polarity allows it to dissolve ionic and polar molecules.

What is a hydration shell?

Sphere of water molecules around a dissolved ion.

What types of molecules are hydrophilic?

Polar or charged molecules.

What types are hydrophobic?

Nonpolar molecules.

What is Avogadro’s number?

6.02 × 10²³ particles per mole.

What is molarity (M)?

Moles of solute per liter of solution.

How do you calculate molar mass?

Add the atomic masses of all atoms in a molecule.

What is an acid?

A substance that increases H⁺ concentration.

What is a base?

A substance that decreases H⁺ concentration.

What does pH measure?

Hydrogen ion concentration.

What does a lower pH indicate?

Higher acidity and more H⁺ ions.

What is a buffer?

A substance that resists changes in pH by accepting or donating H⁺.