Water

STANDARD

Water

Organic

Nucleic Acid

Carbohydrate

Lipid

Protein

Water

Standard Level

Water Structure Hydrogen Bonds Cohesive Properties Solvent Properties Physical Properties

SL Content Statements

A1.1.1

Water as the medium for life
Students should appreciate that the first cells originated in water and that water remains the medium in which most processes of life occur.
A1.1.2

Hydrogen bonds as a consequence of the polar covalent bonds within water molecules
Students should understand that polarity of covalent bonding within water molecules is due to unequal sharing of electrons and that hydrogen bonding due to this polarity occurs between water molecules. Students should be able to represent two or more water molecules and hydrogen bonds between them with the notation shown below to indicate polarity.
A1.1.3

Cohesion of water molecules due to hydrogen bonding and consequences for organisms
Include transport of water under tension in xylem and the use of water surfaces as habitats due to the effect known as surface tension.
A1.1.4

Adhesion of water to materials that are polar or charged and impacts for organisms
Include capillary action in soil and in plant cell walls.
A1.1.5

Solvent properties of water linked to its role as a medium for metabolism and for transport in plants and animals
Emphasize that a wide variety of hydrophilic molecules dissolve in water and that most enzymes catalyse reactions in aqueous solution. Students should also understand that the functions of some molecules in cells depend on them being hydrophobic and insoluble.
A1.1.6

Physical properties of water and the consequences for animals in aquatic habitats
Include buoyancy, viscosity, thermal conductivity and specific heat capacity. Contrast the physical properties of water with those of air and illustrate the consequences using examples of animals that live in water and in air or on land, such as the black-throated loon (Gavia arctica) and the ringed seal (Pusa hispida).
D2.3.1

Solvation with water as the solvent
Include hydrogen bond formation between solute and water molecules, and attractions between both positively and negatively charged ions and polar water molecules.

Water Structure Hydrogen Bonds Cohesive Properties Solvent Properties Physical Properties

Water

Standard Level

SL Content Statements

A1.1.1

Water as the medium for life

Students should appreciate that the first cells originated in water and that water remains the medium in which most processes of life occur.

A1.1.2

Hydrogen bonds as a consequence of the polar covalent bonds within water molecules

A1.1.3

Cohesion of water molecules due to hydrogen bonding and consequences for organisms

Include transport of water under tension in xylem and the use of water surfaces as habitats due to the effect known as surface tension.

A1.1.4

Adhesion of water to materials that are polar or charged and impacts for organisms

Include capillary action in soil and in plant cell walls.

A1.1.5

Solvent properties of water linked to its role as a medium for metabolism and for transport in plants and animals

Emphasize that a wide variety of hydrophilic molecules dissolve in water and that most enzymes catalyse reactions in aqueous solution. Students should also understand that the functions of some molecules in cells depend on them being hydrophobic and insoluble.

A1.1.6

Physical properties of water and the consequences for animals in aquatic habitats

D2.3.1

Solvation with water as the solvent

Include hydrogen bond formation between solute and water molecules, and attractions between both positively and negatively charged ions and polar water molecules.