Ch Properties of Water

H 2 O - Water What you already know is that water is a __________ compound connecting __ Oxygen and __ Hydrogen atoms by the means of __ Oxygen and __ Hydrogen atoms by the means of _____________ bonds _____________ bonds Oxygen engages in ___ covalent bonds Oxygen engages in ___ covalent bonds Hydrogen in ___ covalent bond Hydrogen in ___ covalent bond Structure is not symmetrical due to unshared Ve- Structure is not symmetrical due to unshared Ve- VSEPR shape of water is _____________ VSEPR shape of water is _____________

Water has a ‘bent shape’

Electronegativity of H and O Define Electronegativity Define Electronegativity Oxygen has a ______ electronegativity Hydrogen has a ______ electronegativity Oxygen attracts shared valence e-, becomes____ Oxygen attracts shared valence e-, becomes____ partially negative: δ- Hydrogen loses shared valence e- becomes____ Hydrogen loses shared valence e- becomes____ partially positive: δ+ Overall molecule is __________________ Overall molecule is __________________ neutral !!!!

Water is polar Water behaves like a weak magnet δ+ δ+ δ+ δ+ δ- δ-

Hydrogen Bonds Polar H 2 O molecules are attracted to each other: δ+ to δ- Polar H 2 O molecules are attracted to each other: δ+ to δ- Hydrogen bonds form Hydrogen bonds form between the water molecules draw as dotted lines draw as dotted lines No ‘real’ bonds – more like No ‘real’ bonds – more like weak interactions!

High Surface Tension refers to the skin-like properties of water refers to the skin-like properties of water allows objects to float and makes belly flops painful… allows objects to float and makes belly flops painful… It is an inward pointing force that minimizes surface area – drop formation! It is an inward pointing force that minimizes surface area – drop formation!

High Boiling Point of Water Boiling Point of Water: 100 o C Boiling Point of Water: 100 o C Reason: Hydrogen bonds hold water molecules together preventing evaporation/boiling Reason: Hydrogen bonds hold water molecules together preventing evaporation/boiling Water has a low vapor pressure Water has a low vapor pressure

Ice - an Unusual Solid Ice - an Unusual Solid Freezing point of water: 0 o Celsius Freezing point of water: 0 o Celsius Generally: solids are denser than liquids! Generally: solids are denser than liquids! Exception Water: Ice has a honeycomb structure and a lower density than its liquid Exception Water: Ice has a honeycomb structure and a lower density than its liquid ice floats! ice floats! Ice insulates and protects organisms in winter Ice insulates and protects organisms in winter

Structure of Ice

Wash with water and soap! Water is actually not good for washing away dirt and grime – due to surface tension Water is actually not good for washing away dirt and grime – due to surface tension Surfactants are chemicals that reduce the surface tension Surfactants are chemicals that reduce the surface tension soap or, detergents… soap or, detergents…