Water - The Medium of Life

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Questions and Answers

What is the primary reason water has a bent molecular shape?

There are forces of attraction between hydrogen molecules.

Oxygen pulls electrons more strongly than hydrogen. (correct)

It has a higher boiling point than other substances.

It is a spherical molecule that collapses under pressure.

What percentage of a living organism's composition can be water?

60-95% (correct)

20-40%

40-60%

80-100%

Which property of water is primarily attributed to hydrogen bonding?

Its ability to dissolve other substances. (correct)

Its capacity to conduct electricity.

Its low freezing point.

Its high density compared to other liquids.

What is the consequence of water's high specific heat capacity?

It resists temperature changes. Signup and view all the answers

Which of the following statements about adhesion is correct?

It allows water to form hydrogen bonds with other substances. Signup and view all the answers

What does high specific heat capacity of water imply for living organisms?

Large amounts of energy are required to change water's temperature. Signup and view all the answers

Which of the following physical properties of water allows it to support the weight of floating objects?

Buoyancy Signup and view all the answers

How does water's viscosity compare to that of air?

Water has much higher viscosity than air. Signup and view all the answers

What biological adaptation might mammals have to cope with high thermal conductivity in water?

A layer of blubber Signup and view all the answers

Which factor contributes most to water's high specific heat capacity?

Hydrogen bonding Signup and view all the answers

Why do waterborne animals often exhibit features like streamlining and flippers?

To withstand the high viscosity of water. Signup and view all the answers

How does the thermal conductivity of water compare to that of air?

Water has higher thermal conductivity than air. Signup and view all the answers

Which property of water is responsible for its ability to resist rapid temperature changes?

High specific heat capacity Signup and view all the answers

What is the main reason water exhibits high surface tension?

The cohesive force generated by many hydrogen bonds. Signup and view all the answers

How does adhesion contribute to capillary action in plants?

It facilitates the movement of water against gravity in narrow spaces. Signup and view all the answers

Which statement accurately describes hydrophilic substances?

They dissolve well in water due to their charge or polarity. Signup and view all the answers

What role does water's polarity play in its ability as a solvent?

It allows water molecules to form shells around dissolved particles. Signup and view all the answers

What is primarily responsible for the ability of small animals to walk on water?

Cohesion and high surface tension of water. Signup and view all the answers

Study Notes

Water as the Medium of Life

Water has existed on Earth for at least 3.8 billion years, contributing to the planet's development.
Life began in water, which covers about 70% of Earth's surface.
Organisms are made up of 60-95% water, depending on the species.

Composition and Structure of Water

Water is a bent molecule, consisting of one oxygen atom and two hydrogen atoms (H2O).
Oxygen is slightly negative, while hydrogen is slightly positive, leading to polar covalent bonds.
Higher electronegativity of oxygen pulls electrons toward it, creating hydrogen bonds among water molecules.

Properties of Water

Cohesion: Attractive force between identical molecules; hydrogen bonds lead to high surface tension, enabling small animals to walk on water and facilitating water transport in plants via xylem.
Adhesion: Attractive force between different molecules; allows for capillary action, crucial for water movement in plant stems against gravity.
Solvent: Water's polarity makes it an excellent solvent for charged or polar substances, forming shells around dissolved particles and disrupting hydrogen bonds.
Hydrophilic vs. Hydrophobic: Hydrophilic substances (like ions and polar molecules) dissolve well in water, while hydrophobic substances (like oils and large nonpolar molecules) do not. This property is fundamental for cell membrane structure.

Physical Properties of Water

Specific Heat Capacity: Water has a high specific heat capacity due to extensive hydrogen bonding, requiring considerable energy to increase its temperature, providing stable conditions for organisms.
Thermal Conductivity: Water effectively transfers heat, with higher thermal conductivity than air, influencing adaptation in waterborne mammals (like the Ringed seal) for heat retention.
Viscosity: Water's higher viscosity compared to air affects movement; aquatic animals adapt with streamlined bodies and fins to reduce resistance to flow.
Buoyancy: Upward thrust in water is greater than in air; the density of ice allows it to float, while heavier animals may need structures like ice to support buoyancy.

Biological Implications

High cohesion results in significant surface tension, supporting small life forms.
Adhesion enables efficient nutrient and water transport in plants.
The ability of water to resist temperature changes helps sustain stable aquatic environments, vital for various ecosystems.
Adaptations in organisms like seals and loons illustrate the physical property differences between air and water, influencing design and survival strategies in different habitats.

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Description

Explore the vital role of water in sustaining life on Earth. This quiz delves into geological evidence of water's existence and its importance to all living organisms. Understand how water has shaped life and the planet's history over billions of years.