Chapter 2.1: Water

What is electronegativity?

The tendency of an atom to attract electrons toward itself in a chemical bond

Which two elements discussed are highly electronegative?

Oxygen and nitrogen

What is a polar bond?

A bond where electrons are shared unequally between atomsn

What causes a bond to become polar?

A difference in electronegativity between atoms

What do δ⁺ and δ⁻ represent?

Partial positive and partial negative charges

Why are the O-H bonds in water polar?

Oxygen is more electronegative than hydrogen, so it attracts the bonding electrons more strongly

What is the shape of a water molecule?

Bent, with a bond angle of about 104.3 degrees

Why is water a polar molecule?

Its bent shape prevents the polar O-H bonds from canceling each other out

What is a dipole?

A molecule or bend with a partial positive end and a partial negative end

Why is CO₂ nonpolar even though its bonds are polar?

CO2 is linear, so the bond polarities cancel each other out

What determines many of water’s solvent properties?

Its polar nature

What types of substances dissolve in water?

Opposite charges attract through electrostatic interactions

What does hydrophilic mean?

“Water-loving”; substances that tend to dissolve or interact well with water

Give examples of hydrophilic substances

KCl, alcohols, amines, and caarboxylic acids

What are hydrocarbons?

Compounds containing only carbon and hydrogen

Are hydrocarbons polar or nonpolar?

Nonpolar

Why don’t nonpolar substances dissolve well in water?

They cannot form strong interactions with polar water molecules

What does hydrophobic mean?

“Water-hating”; substances that do not dissolve well in water

What happens when oil and water are mixed?

They separate into two layers because oil is nonpolar and water is polar

What is a hydrophobic interaction?

The tendency of nonpolar molecules to group together and avoid contact with water

What is an amphipathic molecule?

A molecule with both hydrophilic and hydrophobic regions

What are the two parts of a fatty acid?

A polar hydrophilic head and a nonpolar hydrophobic tail

What does the hydrophilic head of a fatty acid interact with?

Water

What does the hydrophobic tail avoid?

Water

What is a micelle?

A structure where amphipathic molecules arrange with their hydrophilic heads facing water and hydrophobic tails away from water

What are van der Waals interactions?

Weak attractions between molecules caused by temporary dipoles

How do temporary dipoles form?

Electrons briefly become unevenly distributed within a molecules

How do van der Waals interactions compare with dipole interactions?

They are generally weaker and short-lived

Why is molecular polarity important in cells?

It determines how molecules interact with water and with each other, influencing how molecules organize into structures