Water and Life

Question-and-answer flashcards covering key concepts about the distribution, structure, properties, and essential role of water in life as described in the notes.

What percentage of Earth’s surface is covered by water?

Almost 75%.

Where is most of Earth’s water found?

In the oceans (saltwater).

What is the chemical formula of water?

H2O (one oxygen atom and two hydrogen atoms).

Which atom in a water molecule is more electronegative, and what charges does this create?

Oxygen is more electronegative, giving it a slightly negative charge while the hydrogens carry slight positive charges.

What type of bonds form between water molecules?

Hydrogen bonds.

Name three properties of water explained by hydrogen bonding.

Cohesion, adhesion, and capillary action.

Define cohesion.

Water molecules tend to stick together.

Define adhesion.

Bonding of a water molecule to another substance (e.g., the sides of a leaf's veins).

What causes capillary action?

The continual breaking and reforming of hydrogen bonds allows water to move up narrow spaces against gravity.

Why does water have a relatively high boiling point?

Hydrogen bonds between water molecules hold them together, giving water a high boiling point (100°C).

What happens to water as it freezes?

Water expands; ice is less dense than liquid water and floats.

What role does water play in the transport of substances in plants and animals?

Cohesion and adhesion enable water transport in plants (through roots and stems) and in animals through small blood vessels.

What are the two main biochemical processes involving water mentioned in the notes?

Photosynthesis and cellular respiration.

What is the photosynthesis equation as given in the notes?

6CO2 + 6H2O + Energy → C6H12O6 + 6O2.

What is the cellular respiration equation as given in the notes?

C6H12O6 + 6O2 → 6CO2 + 6H2O + Energy.

What percentage of the human body is water?

About 70%.

What is another name for water mentioned in the notes?

Dihydrogen oxide, or dihydrogen monoxide.

What is water's polarity?

The polarity is a difference in electrical charge between different parts of the same molecule, making water a polar molecule.

Why is water essential for life?

Water is needed by all known forms of life, life started in water, and water participates in many biochemical reactions.