SolutionsSolutions

Liquid Water and Its PropertiesLiquid Water and Its Properties

ReviewReview

What is meant by the term polarity?What is meant by the term polarity? It refers to the net molecular dipole It refers to the net molecular dipole

arising out of electronegativity arising out of electronegativity differences between covalently bonded differences between covalently bonded atoms.atoms.

This means the overall molecule has a This means the overall molecule has a positive side and a negative side.positive side and a negative side.

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The Water MoleculeThe Water Molecule

Are the O-H bonds in a molecule of Are the O-H bonds in a molecule of water polar?water polar? Yes; the oxygen atoms have a higher Yes; the oxygen atoms have a higher

electronegativity, so they have a partial electronegativity, so they have a partial negative charge when bonded to negative charge when bonded to hydrogen.hydrogen.

This leaves the hydrogen atoms as This leaves the hydrogen atoms as partially exposed protons.partially exposed protons.

The Water MoleculeThe Water Molecule

What is the shape of a water What is the shape of a water molecule?molecule? BentBent

Is water a dipole?Is water a dipole? Yes, the bent shape allows a positive Yes, the bent shape allows a positive

side and a negative side.side and a negative side.

The Water MoleculeThe Water Molecule

What are the predominant What are the predominant intermolecular forces in water?intermolecular forces in water? Hydrogen bondsHydrogen bonds

Surface PropertiesSurface Properties

Surface tension:Surface tension: An inward force that tends to minimize An inward force that tends to minimize

the surface area of a liquid; it causes the the surface area of a liquid; it causes the surface to behave as if it were a thin skin.surface to behave as if it were a thin skin.

Draw arrows on the picture to indicate Draw arrows on the picture to indicate the hydrogen bonds. Which molecules the hydrogen bonds. Which molecules have the least connections?have the least connections? The outermost molecules are only pulled in The outermost molecules are only pulled in

one direction, which causes the surface one direction, which causes the surface tension.tension.

Surface PropertiesSurface Properties

Surface PropertiesSurface Properties

Surfactant:Surfactant: Any substance with molecules Any substance with molecules

that interfere with hydrogen that interfere with hydrogen bonding between water bonding between water molecules, reducing surface molecules, reducing surface tensiontension

Soaps and detergentsSoaps and detergents AKA “wetting agents” – they AKA “wetting agents” – they

help the water spread out and help the water spread out and cover a surfacecover a surface

Water Vapor and IceWater Vapor and Ice What is the melting point of a What is the melting point of a

substance?substance? The temperature at which it changes from a The temperature at which it changes from a

solid to a liquidsolid to a liquid What is the freezing point of a What is the freezing point of a

substance?substance? The temperature at which it changes from a The temperature at which it changes from a

liquid to a solidliquid to a solid How is the melting point related to the How is the melting point related to the

freezing point?freezing point? They are the same numerical value.They are the same numerical value.

Water Vapor and IceWater Vapor and Ice

What is the change from a liquid to What is the change from a liquid to gas called?gas called? VaporizationVaporization

What is the name for vaporization just What is the name for vaporization just on the surface of the liquid?on the surface of the liquid? EvaporationEvaporation

What is vaporization throughout a What is vaporization throughout a liquid?liquid? BoilingBoiling

Water Vapor and IceWater Vapor and Ice

What is the change from gas to What is the change from gas to liquid called?liquid called? CondensationCondensation

What is the name of the temperature What is the name of the temperature at which a gas changes to a liquid?at which a gas changes to a liquid? Boiling pointBoiling point

Evaporation and Evaporation and CondensationCondensation

What examples of evaporation and What examples of evaporation and condensation are found in normal condensation are found in normal day-to-day situations?day-to-day situations?

IceIce

Are solids typically more or less dense Are solids typically more or less dense than liquids? For example, is solid lead than liquids? For example, is solid lead more or less dense than molten lead at more or less dense than molten lead at the same temperature?the same temperature? More dense – the particles are closer to each More dense – the particles are closer to each

other in the solidother in the solid Does water follow this trend? How can Does water follow this trend? How can

you tell?you tell? No, ice is less dense than liquid water. This No, ice is less dense than liquid water. This

is obvious because ice floats in liquid water.is obvious because ice floats in liquid water.

IceIce

How does hydrogen bonding affect the How does hydrogen bonding affect the structure of ice?structure of ice? Liquid water has hydrogen bonds, but the Liquid water has hydrogen bonds, but the

molecules also have enough energy to move molecules also have enough energy to move around quite a bit. As the temperature around quite a bit. As the temperature lowers and the molecules lose energy they lowers and the molecules lose energy they slow down. At the freezing point, the slow down. At the freezing point, the hydrogen bonds “lock” the molecules into hydrogen bonds “lock” the molecules into place within a crystalline structure. This place within a crystalline structure. This crystal pattern is an open-faced hexagon crystal pattern is an open-faced hexagon shape, which spreads the molecules out shape, which spreads the molecules out compared to those in liquid water.compared to those in liquid water.

IceIce

IceIce

Is the floating nature of ice Is the floating nature of ice important for life? Why or why not?important for life? Why or why not? Yes. It creates an insulating barrier Yes. It creates an insulating barrier

above cold water. It allows deep water above cold water. It allows deep water (under high pressure) to maintain a (under high pressure) to maintain a temperature of 4temperature of 4ooC.C.