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Biology > Structure of Water and Hydrogen Bonds > Flashcards

Structure of Water and Hydrogen Bonds Flashcards

1
Q

What is the molecular structure of a water molecule?

A

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

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2
Q

What is water’s polarity?

A

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

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3
Q

Why is hydrogen bonding important in water?

A

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

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4
Q

What is specific heat capacity in water?

A

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

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5
Q

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

A

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

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6
Q

What are lone pairs in a water molecule?

A

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

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7
Q

What is a hydrogen bond?

A

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

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8
Q

Why are hydrogen bonds important for water’s properties?

A

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

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9
Q

What is a meniscus?

A

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.

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10
Q

What causes a concave meniscus?

A

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

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11
Q

What causes a convex meniscus?

A

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

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12
Q

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

A

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

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13
Q

How does water’s polarity contribute to hydrogen bonding?

A

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

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14
Q

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

A

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

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15
Q

What is the difference between cohesion and adhesion in water?

A

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

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16
Q

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

A

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

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17
Q

Why does ice expand when it freezes?

A

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

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18
Q

How do hydrogen bonds contribute to capillary action?

A

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

19
Q

What does “hydrophilic” mean?

A

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

20
Q

What does “hydrophobic” mean?

A

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

21
Q

What is a solvent?

A

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.

22
Q

What is a solute?

A

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

23
Q

How does water act as a solvent in biological systems?

A

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

24
Q

What are examples of hydrophilic substances?

A

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

25
Q

What are examples of hydrophobic substances?

A

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

26
Q

Why are hydrophilic and hydrophobic properties important in biology?

A

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

27
Q

How do hydrophobic interactions help form cell membranes?

A

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

28
Q

What role does water play in dissolving ionic compounds?

A

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

29
Q

How do solutes like salt dissolve in water?

A

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.

30
Q

Why can’t hydrophobic substances dissolve in water?

A

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

31
Q

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

A

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

32
Q

Why does water have a high heat of vaporization?

A

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

33
Q

What is cohesion in water?

A

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

34
Q

What is adhesion in water?

A

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

35
Q

Why does ice float on water?

A

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

36
Q

How does floating ice help aquatic life?

A

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

37
Q

What is capillary action?

A

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

38
Q

How does water’s high heat capacity benefit life?

A

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

39
Q

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

A

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

40
Q

How do cohesion and adhesion work together in water?

A

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

41
Q

What would happen if ice were denser than liquid water?

A

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

42
Q

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

A

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

43
Q

How do organisms benefit from water’s properties?

A

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

Biology (1 decks)

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