Biology Chapter 3: Water and Life

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Questions and Answers

What defines an aqueous solution?

It is a solution with a solid solute.

It is a solution that is acidic in nature.

It is a solution in which water is the solvent. (correct)

It is a solution containing multiple phases.

Which of the following statements is true regarding hydrophilic substances?

They have an affinity for water. (correct)

They have no interaction with water.

They repel water molecules.

They do not dissolve in water.

What is the primary reason water is termed 'the solvent of life'?

It readily forms hydrogen bonds. (correct)

It is the only solvent known.

It has a high boiling point.

It can only dissolve ionic compounds.

In the context of water dissociation, what does a hydroxide ion (OH-) represent?

A water molecule that has lost a proton. Signup and view all the answers

How is molarity defined?

As the number of moles of solute per liter of solution. Signup and view all the answers

What is the effect of adding an acid to a solution?

It increases the H+ concentration. Signup and view all the answers

Which of the following describes a solute?

The substance that is dissolved in a solution. Signup and view all the answers

What occurs during the hydration of an ionic compound in water?

Water molecules surround each ion, forming a hydration shell. Signup and view all the answers

What happens to the concentrations of H+ and OH- in pure water?

They are equal. Signup and view all the answers

Why are changes in pH significant for living organisms?

They can drastically affect the chemistry of a cell. Signup and view all the answers

What property of water allows it to absorb and release heat with minimal temperature change?

High specific heat Signup and view all the answers

Which process describes water's ability to cool itself as it evaporates?

Evaporative cooling Signup and view all the answers

How does cohesion in water contribute to plant life?

By transporting water against gravity Signup and view all the answers

What characteristic of ice causes it to float on water?

It is less dense than liquid water Signup and view all the answers

What term describes the measure of how difficult it is to break the surface of a liquid?

Surface tension Signup and view all the answers

What role does water play in temperature moderation?

It absorbs and releases heat slowly Signup and view all the answers

What is the heat of vaporization in the context of water?

The heat absorbed for 1 gram to evaporate Signup and view all the answers

Which statement about hydrogen bonds in water is correct?

They release energy when formed. Signup and view all the answers

What is an emergent property of water that is crucial for life on Earth?

Versatility as a solvent Signup and view all the answers

How does adhesion in water assist plants?

By helping counteract gravity Signup and view all the answers

Study Notes

Chapter 3: Water and Life

Water is a polar molecule due to polar covalent bonds
Opposite ends of the water molecule have opposite charges
Polarity allows water molecules to form hydrogen bonds with each other
Water's electron arrangement gives oxygen two partial negative charges
Hydrogen bonds between water molecules give water unique properties
Hydrogen bonds are responsible for water's high surface tension which allows some insects to walk on water
Water has high specific heat; large amounts of heat are absorbed or released with only slight temperature fluctuations
Water's specific heat stabilizes temperatures
Evaporation is the transformation of a substance from liquid to gas
Heat of vaporization is the heat a liquid needs to absorb for 1 gram to be converted to gas
Evaporative cooling occurs when a liquid evaporates, its remaining surface cools
Water's high specific heat and evaporative cooling help stabilize temperatures in organisms and bodies of water
Ice floats in liquid water because hydrogen bonds in ice are more ordered and make ice less dense
If ice sank, all bodies of water would eventually freeze solid, which makes life impossible on Earth
A solution is a mixture that is homogeneous; a liquid dissolving agent is a solvent
A solute is the substance that is dissolved in a solution
Water is a versatile solvent due to its polarity
Water is an effective solvent because it readily forms hydrogen bonds
When an ionic compound is dissolved in water, each ion is surrounded by a sphere of water molecules; this is called a hydration shell
Most biochemical reactions occur in water, and reactions depend on the concentration of solutes; these factors are important for the chemistry of a cell
Molecular mass is the sum of the masses of all the atoms in a molecule. Numbers are usually measured in moles where one mole=6.02 x 10^23 molecules.
Molarity is the number of moles of solute per liter of solution
Water dissociation releases hydrogen ions (H+) and hydroxide ions (OH-)
The hydrogen atom leaves its electron behind and is transferred as a proton; molecules with an extra proton are known as hydronium ions (H3O+). Molecules that lose a proton are known as hydroxide ions (OH-)
The concentration of H+ and OH- is equal in pure water; adding acids and bases modifies the concentrations
Biologists use the pH scale to describe how acidic or basic something is
An acid increases the H+ concentration in a solution
A base reduces the H+ concentration in a solution
The pH of a solution is determined by the relative concentration of hydrogen ions
Acidic solutions have pH values lower than 7
Basic solutions have pH values greater than 7
Most biological fluids have a pH value between 6 and 8
Buffers are substances that minimize changes in the H+ and OH- concentration in solutions
Most buffers consist of an acid-base pair that combines reversibly with hydrogen ions

The Threat of Acid Precipitation

Acid precipitation refers to rain, snow, or fog below a pH of 5.6
Acid precipitation is a result of pollutants mixing with the water in the air
Acid precipitation damages life in lakes and streams
It also affects soil chemistry, which then leads to the decline of forests.

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Description

Explore the essential properties of water in this quiz focusing on polar molecules, hydrogen bonds, and specific heat. Understand how these properties impact life and ecosystems, as well as phenomena like evaporation and temperature stabilization in organisms. Test your knowledge of the significance of water in biology.