Chemistry of Life and Water is Essential for Life - Class 4

Flashcards covering bond types, electronegativity, water properties, hydrogen bonding, polarity, and emergent properties.

What is a non-polar covalent bond?

Electrons are shared equally between the two bonded atoms, resulting in no partial charges.

What is a polar covalent bond?

Electrons are shared unequally between two bonded atoms, creating partial charges (δ+ and δ−).

What is an ionic bond?

A bond between oppositely charged ions formed by the transfer of electrons.

How do ionic bonds form in terms of electron movement?

One atom donates electrons and another accepts, producing stable charged ions.

What determines the type of bond in a molecule?

Difference in electronegativity between the bonded atoms.

What ΔEN range typically yields a polar covalent bond?

Approximately 0.5 to 1.7.

What ΔEN range typically yields an ionic bond?

Greater than about 1.7.

What is the bond type in HCl?

Polar covalent.

If H has EN 2.1 and Cl has EN 3.0, what is the bond type in HCl?

Polar covalent (ΔEN = 0.9).

How do you determine bond type using electronegativity values?

Identify bonded atoms, calculate ΔEN, and compare to thresholds for nonpolar covalent, polar covalent, and ionic.

What is a hydrogen bond?

A noncovalent attraction between a partially positive hydrogen atom and a partially negative atom (usually O or N) in different molecules.

Are hydrogen bonds covalent or noncovalent?

Noncovalent; electrons are not shared.

Name an emergent property of water due to hydrogen bonding: Cohesion.

Cohesion is the attraction among water molecules, contributing to surface tension.

Name an emergent property: Adhesion.

Adhesion is the attraction of water to other polar molecules, enabling capillary action.

What is meant by water’s high specific heat?

Water can absorb or release large amounts of heat with only small changes in temperature.

What is meant by water’s high heat of vaporization?

It takes a large amount of energy to convert liquid water to vapor, contributing to cooling during evaporation.

Why does ice float on water?

Ice is less dense than liquid water due to a open hydrogen-bonded lattice, allowing life beneath the ice.

Why is water a good solvent for many substances?

Water is polar and can dissolve polar solutes and ions through hydration and ion-dipole interactions.

Why does salt dissolve in water?

Water molecules surround Na+ and Cl− ions via ion-dipole interactions, pulling the crystal apart.

What does hydrophilic mean?

Polar molecules that dissolve in water.

What does hydrophobic mean?

Nonpolar molecules that do not dissolve well in water.

Is water a polar molecule?

Yes, due to polar covalent O–H bonds and a bent geometry creating overall polarity.

Why is CO2 nonpolar despite having polar bonds?

Although CO2 has polar bonds, its linear shape causes dipoles to cancel, making the molecule nonpolar.

How do bond type and molecular shape together influence polarity?

Polarity depends on both bond dipoles (polar vs nonpolar bonds) and the molecule’s geometry (shape).

What is the role of hydrogen bonds in DNA?

Hydrogen bonds hold the two DNA strands together by base-pair interactions.

What is the role of hydrogen bonds in proteins?

Hydrogen bonds help stabilize secondary and tertiary protein structures.

What does polarity mean in biology?

Polarity refers to the distribution of electrical charge leading to partial charges that drive interactions with water and other molecules.

What are polar and nonpolar examples related to water interaction?

Polar molecules are hydrophilic and dissolve in water; nonpolar molecules are hydrophobic and do not.

What is meant by a solvent in biology?

A substance (like water) that dissolves solutes to form a solution.

What are the delta plus and delta minus symbols used for?

They indicate partial positive (δ+) and partial negative (δ−) charges in polar bonds.

What is an emergent property in biology?

A new property that arises from interactions among components at a lower level, not present in the components alone.

What is surface tension an example of in water?

Cohesion between water molecules at the air-water interface.

What enables capillary action in plants?

Adhesion of water to polar surfaces, aiding movement up xylem vessels.

How does evaporative cooling work?

Energy is absorbed when water evaporates, cooling the surrounding environment.

Why is water essential for life on Earth?

Water’s properties (solvent, temperature regulation, hydrogen bonding, and emergent properties) support life’s chemistry and habitats.

What determines molecular polarity when shown in diagrams?

Consider both the bond type (polar vs nonpolar) and the molecular geometry; dipoles may cancel or add.

Why are hydrophobic interactions important in biology?

Nonpolar regions cluster away from water, stabilizing membranes and protein folding.