Water and Life: Key Concepts from Lecture Notes

A comprehensive set of practice Q&A flashcards covering water's properties, its role as solvent, pH chemistry, buffering, and environmental implications from the notes.

What molecule is the biological medium/solvent on Earth that supports life?

Water

What percentage of water do most cells and organisms contain?

About 70–95% water

What is NASA astrobiology's motto related to water?

Follow the water

Approximately how many planets have been found outside our solar system?

About 4000

Which bodies in our solar system have water or subsurface oceans?

Mars has water; several moons of Jupiter and Saturn have subsurface oceans

Name one of the four emergent properties of water related to life.

Cohesive and adhesive behavior

Name another emergent property of water related to life.

Ability to moderate temperature

Name another emergent property of water related to life.

Expansion upon freezing

Name another emergent property of water related to life.

Versatility as a solvent

In a water molecule, which region has partial positive charge (δ+)?

Hydrogen atoms

What does cohesion refer to in water chemistry?

Hydrogen bonds holding water molecules together

What does adhesion refer to in water chemistry?

Attraction between water and other substances (e.g., plant cell walls)

What two properties help water transport in plants against gravity?

Cohesion and adhesion (capillary action)

What is surface tension?

A measure of how hard it is to break the surface of a liquid; related to cohesion

Why does water moderate climate despite temperature fluctuations?

Because it can absorb or release a large amount of heat with only a small change in its own temperature due to high specific heat

What is the specific heat of water?

1 cal/g/°C

What is the relationship between joules and calories?

1 J = 0.239 cal; 1 cal = 4.184 J (also 1 kcal = 1000 cal)

What is evaporative cooling?

As a liquid evaporates, its remaining surface cools; this helps stabilize temperatures

Why does ice float on liquid water?

Hydrogen bonds in ice are more ordered, making ice less dense than liquid water

At what temperature does water reach its greatest density?

4°C

What are the basic terms in solution chemistry: solvent, solute, and aqueous solution?

Solvent is the dissolving agent; solute is the dissolved substance; an aqueous solution has water as the solvent

What is a colloid?

A stable suspension of fine particles in a liquid

When an ionic compound dissolves in water, what forms around ions?

A hydration shell

Why is water a versatile solvent?

Its polarity allows it to form hydrogen bonds with solutes, including non-ionic but polar solutes

What do hydrophilic and hydrophobic mean?

Hydrophilic: loves water; hydrophobic: hates water

Are oil molecules hydrophobic or hydrophilic?

Hydrophobic

What ions are produced when water self-ionizes?

Hydronium ion (H3O+) and hydroxide ion (OH−)

How do acids and bases affect hydrogen ion concentration?

Acids increase [H+]; bases decrease [H+]

What is the pH scale and how is it defined?

pH = -log[H+]; defined at 25°C with [H+] and [OH−] in a constant relationship

What is the pH of a neutral solution at 25°C?

7

Do pH and pOH sum to 14 at 25°C?

Yes

If pH = 3, what is pOH?

11

If [H+] = 10^-3 M, what is [OH−]?

10^-11 M

What is the typical pH range for most biological fluids?

6 to 8

What is molarity and what does it measure?

Molarity (M) is the number of moles of solute per liter of solution

What is Avogadro's number?

6.02 x 10^23 molecules per mole

What is molecular weight measured in?

Grams per mole (g/mol)

What is buffering in biology?

Buffers minimize changes in [H+] and [OH−] by reversible acid-base pairs; keep pH around 7

What is ocean acidification and its cause?

CO2 dissolved in seawater forms carbonic acid, lowering pH; about 25% of human-generated CO2 is absorbed by oceans

What two environmental problems are destroying coral reefs according to the notes?

Ocean acidification and ocean warming

What causes acid rain and what is the pH threshold for it?

Sulfur oxides and nitrogen oxides form acids in the atmosphere; rain/fog/snow with pH < 5.2

What are the environmental impacts of acid precipitation?

Damages life in lakes/streams and changes soil chemistry