Structure of Water and Hydrogen Bonds

Question 1

What is the molecular structure of a water molecule?

Answer 1

A water molecule (H₂O) has one oxygen atom bonded to two hydrogen atoms in a bent shape.

Question 2

What is water’s polarity?

Answer 2

Water has a positive and a negative side due to its shape and electronegativity difference, making it polar.

Question 3

Why is hydrogen bonding important in water?

Answer 3

Hydrogen bonds make water molecules stick together, creating a stable liquid environment for life.

Question 4

What is specific heat capacity in water?

Answer 4

Water absorbs a lot of heat with little temperature change, keeping environments and organisms st

Question 5

What type of bonds connect the atoms in a water molecule?

Answer 5

Covalent bonds connect oxygen to hydrogen atoms in a water molecule by sharing electrons.

Question 6

What are lone pairs in a water molecule?

Answer 6

Lone pairs are unshared electrons on the oxygen atom, giving water a bent shape and contributing to its polarity.

Question 7

What is a hydrogen bond?

Answer 7

A hydrogen bond is a weak attraction between the partially positive hydrogen of one water molecule and the partially negative oxygen of another.

Question 8

Why are hydrogen bonds important for water’s properties?

Answer 8

Hydrogen bonds create cohesion, adhesion, surface tension, high heat capacity, and allow water to be a liquid at room temperature.

Question 9

What is a meniscus?

Answer 9

A meniscus is the curved surface of water in a container due to adhesion of water to the container walls and cohesion among water molecules.

Question 10

What causes a concave meniscus?

Answer 10

A concave meniscus forms when water molecules are more attracted to the walls of a container than to each other.

Question 11

What causes a convex meniscus?

Answer 11

A convex meniscus forms when a liquid, like mercury, is more attracted to itself than to the container walls.

Question 12

What is surface tension, and how does it relate to hydrogen bonds?

Answer 12

Surface tension is the tight surface layer formed by water molecules at the surface due to hydrogen bonds pulling them together.

Question 13

How does water’s polarity contribute to hydrogen bonding?

Answer 13

Water’s polarity creates partial positive (hydrogen) and negative (oxygen) ends, allowing them to form hydrogen bonds with other polar molecules.

Question 14

What role do lone pairs on oxygen play in water’s properties?

Answer 14

Lone pairs on oxygen create areas of partial negative charge, essential for forming hydrogen bonds with other water molecules.

Question 15

What is the difference between cohesion and adhesion in water?

Answer 15

Cohesion is water molecules sticking to each other; adhesion is water molecules sticking to other surfaces.

Question 16

How does hydrogen bonding affect water’s boiling and freezing points?

Answer 16

Hydrogen bonds require significant energy to break, raising water’s boiling point, and form a lattice structure when freezing, lowering its density.

Question 17

Why does ice expand when it freezes?

Answer 17

Hydrogen bonds form a structured lattice in ice, spreading water molecules apart and making ice less dense than liquid water.

Question 18

How do hydrogen bonds contribute to capillary action?

Answer 18

Hydrogen bonds allow water to stick to itself (cohesion) and to other surfaces (adhesion), enabling water to move up thin tubes against gravity.

Question 19

What does “hydrophilic” mean?

Answer 19

Hydrophilic means “water-loving”; it describes substances that dissolve well in water, like salts and sugars, due to their polarity or charge.

Question 20

What does “hydrophobic” mean?

Answer 20

Hydrophobic means “water-fearing”; it describes substances that do not dissolve well in water, like oils and fats, due to their non-polar nature.

Question 21

What is a solvent?

Answer 21

A solvent is a substance that dissolves other substances (solutes). Water is known as the “universal solvent” because it dissolves many polar and ionic substances.

Question 22

What is a solute?

Answer 22

A solute is a substance that is dissolved in a solvent. For example, salt is a solute when dissolved in water.

Question 23

How does water act as a solvent in biological systems?

Answer 23

Water dissolves ions and polar molecules, allowing chemical reactions to occur and substances to be transported in cells and organisms.

Question 24

What are examples of hydrophilic substances?

Answer 24

Examples include salt (NaCl), sugar, and many proteins, which dissolve well in water due to their polarity or ionic nature.

Question 25

What are examples of hydrophobic substances?

Answer 25

Examples include oils, fats, and hydrocarbons, which do not mix with water because they are non-polar.

Question 26

Why are hydrophilic and hydrophobic properties important in biology?

Answer 26

These properties allow for the formation of cell membranes (hydrophobic interior and hydrophilic exterior) and the compartmentalization of cells.

Question 27

How do hydrophobic interactions help form cell membranes?

Answer 27

Hydrophobic tails of phospholipids repel water and group together, forming a bilayer that makes up cell membranes, with hydrophilic heads facing outward.

Question 28

What role does water play in dissolving ionic compounds?

Answer 28

Water’s polarity allows it to surround and separate positive and negative ions, effectively dissolving compounds like salts.

Question 29

How do solutes like salt dissolve in water?

Answer 29

The positive end (hydrogens) of water molecules surrounds the negative chloride ions, while the negative end (oxygen) surrounds the positive sodium ions, breaking them apart.

Question 30

Why can’t hydrophobic substances dissolve in water?

Answer 30

Hydrophobic substances lack a charge or polarity, so they do not interact well with polar water molecules, leading them to separate instead.

Question 31

Why is water’s role as a solvent crucial for chemical reactions in cells?

Answer 31

Water dissolves reactants and facilitates their interactions, allowing essential biochemical processes to occur within cells.

Question 32

Why does water have a high heat of vaporization?

Answer 32

It takes a lot of energy to turn water into gas, which helps cool organisms through sweating.

Question 33

What is cohesion in water?

Answer 33

Cohesion is water molecules sticking together, which creates surface tension and supports water transport in plants.

Question 34

What is adhesion in water?

Answer 34

Adhesion is water sticking to other surfaces, helping transport nutrients in plants and animals.

Question 35

Why does ice float on water?

Answer 35

Ice is less dense than water because it expands when it freezes, allowing it to float.

Question 36

How does floating ice help aquatic life?

Answer 36

Ice insulates the water below, keeping it warm enough for aquatic life during cold weather.

Question 37

What is capillary action?

Answer 37

Capillary action is water moving up thin tubes, like in plant roots and blood vessels, due to cohesion and adhesion.

Question 38

How does water’s high heat capacity benefit life?

Answer 38

It keeps temperature changes slow and steady, protecting organisms from extreme temperature shifts.

Question 39

What is the significance of water’s high heat of vaporization?

Answer 39

It helps cool organisms through evaporation, like sweating, preventing overheating.

Question 40

How do cohesion and adhesion work together in water?

Answer 40

Cohesion keeps water together; adhesion helps it stick to other surfaces, crucial for transporting nutrients.

Question 41

What would happen if ice were denser than liquid water?

Answer 41

Ice would sink, causing bodies of water to freeze from the bottom up, making life in water impossible.

Question 42

Why is water’s lower density as a solid unusual?

Answer 42

Most substances are denser as solids, but water’s hydrogen bonds make ice expand and float.

Question 43

How do organisms benefit from water’s properties?

Answer 43

Water’s properties support stable environments, nutrient transport, temperature regulation, and cellular functions.