Structure of Water and Hydrogen Bonds Flashcards
What is the molecular structure of a water molecule?
A water molecule (H₂O) has one oxygen atom bonded to two hydrogen atoms in a bent shape.
What is water’s polarity?
Water has a positive and a negative side due to its shape and electronegativity difference, making it polar.
Why is hydrogen bonding important in water?
Hydrogen bonds make water molecules stick together, creating a stable liquid environment for life.
What is specific heat capacity in water?
Water absorbs a lot of heat with little temperature change, keeping environments and organisms st
What type of bonds connect the atoms in a water molecule?
Covalent bonds connect oxygen to hydrogen atoms in a water molecule by sharing electrons.
What are lone pairs in a water molecule?
Lone pairs are unshared electrons on the oxygen atom, giving water a bent shape and contributing to its polarity.
What is a hydrogen bond?
A hydrogen bond is a weak attraction between the partially positive hydrogen of one water molecule and the partially negative oxygen of another.
Why are hydrogen bonds important for water’s properties?
Hydrogen bonds create cohesion, adhesion, surface tension, high heat capacity, and allow water to be a liquid at room temperature.
What is a meniscus?
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.
What causes a concave meniscus?
A concave meniscus forms when water molecules are more attracted to the walls of a container than to each other.
What causes a convex meniscus?
A convex meniscus forms when a liquid, like mercury, is more attracted to itself than to the container walls.
What is surface tension, and how does it relate to hydrogen bonds?
Surface tension is the tight surface layer formed by water molecules at the surface due to hydrogen bonds pulling them together.
How does water’s polarity contribute to hydrogen bonding?
Water’s polarity creates partial positive (hydrogen) and negative (oxygen) ends, allowing them to form hydrogen bonds with other polar molecules.
What role do lone pairs on oxygen play in water’s properties?
Lone pairs on oxygen create areas of partial negative charge, essential for forming hydrogen bonds with other water molecules.
What is the difference between cohesion and adhesion in water?
Cohesion is water molecules sticking to each other; adhesion is water molecules sticking to other surfaces.
How does hydrogen bonding affect water’s boiling and freezing points?
Hydrogen bonds require significant energy to break, raising water’s boiling point, and form a lattice structure when freezing, lowering its density.
Why does ice expand when it freezes?
Hydrogen bonds form a structured lattice in ice, spreading water molecules apart and making ice less dense than liquid water.
How do hydrogen bonds contribute to capillary action?
Hydrogen bonds allow water to stick to itself (cohesion) and to other surfaces (adhesion), enabling water to move up thin tubes against gravity.
What does “hydrophilic” mean?
Hydrophilic means “water-loving”; it describes substances that dissolve well in water, like salts and sugars, due to their polarity or charge.
What does “hydrophobic” mean?
Hydrophobic means “water-fearing”; it describes substances that do not dissolve well in water, like oils and fats, due to their non-polar nature.
What is a solvent?
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.
What is a solute?
A solute is a substance that is dissolved in a solvent. For example, salt is a solute when dissolved in water.
How does water act as a solvent in biological systems?
Water dissolves ions and polar molecules, allowing chemical reactions to occur and substances to be transported in cells and organisms.
What are examples of hydrophilic substances?
Examples include salt (NaCl), sugar, and many proteins, which dissolve well in water due to their polarity or ionic nature.
What are examples of hydrophobic substances?
Examples include oils, fats, and hydrocarbons, which do not mix with water because they are non-polar.
Why are hydrophilic and hydrophobic properties important in biology?
These properties allow for the formation of cell membranes (hydrophobic interior and hydrophilic exterior) and the compartmentalization of cells.
How do hydrophobic interactions help form cell membranes?
Hydrophobic tails of phospholipids repel water and group together, forming a bilayer that makes up cell membranes, with hydrophilic heads facing outward.
What role does water play in dissolving ionic compounds?
Water’s polarity allows it to surround and separate positive and negative ions, effectively dissolving compounds like salts.
How do solutes like salt dissolve in water?
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.
Why can’t hydrophobic substances dissolve in water?
Hydrophobic substances lack a charge or polarity, so they do not interact well with polar water molecules, leading them to separate instead.
Why is water’s role as a solvent crucial for chemical reactions in cells?
Water dissolves reactants and facilitates their interactions, allowing essential biochemical processes to occur within cells.
Why does water have a high heat of vaporization?
It takes a lot of energy to turn water into gas, which helps cool organisms through sweating.
What is cohesion in water?
Cohesion is water molecules sticking together, which creates surface tension and supports water transport in plants.
What is adhesion in water?
Adhesion is water sticking to other surfaces, helping transport nutrients in plants and animals.
Why does ice float on water?
Ice is less dense than water because it expands when it freezes, allowing it to float.
How does floating ice help aquatic life?
Ice insulates the water below, keeping it warm enough for aquatic life during cold weather.
What is capillary action?
Capillary action is water moving up thin tubes, like in plant roots and blood vessels, due to cohesion and adhesion.
How does water’s high heat capacity benefit life?
It keeps temperature changes slow and steady, protecting organisms from extreme temperature shifts.
What is the significance of water’s high heat of vaporization?
It helps cool organisms through evaporation, like sweating, preventing overheating.
How do cohesion and adhesion work together in water?
Cohesion keeps water together; adhesion helps it stick to other surfaces, crucial for transporting nutrients.
What would happen if ice were denser than liquid water?
Ice would sink, causing bodies of water to freeze from the bottom up, making life in water impossible.
Why is water’s lower density as a solid unusual?
Most substances are denser as solids, but water’s hydrogen bonds make ice expand and float.
How do organisms benefit from water’s properties?
Water’s properties support stable environments, nutrient transport, temperature regulation, and cellular functions.
