IB biology : Topic A.1.1 - water

bond inside a water molecule

polar covalent bond

breaking polar bond

• mechanical force is needed

• weak, intermolecular force

how to represent a covalent polar bond between water molecules

( add a little delta )

cohesion

process in which “like” polar molecules are attracted to each other’s positive and negative parts.

cohesion consequences

• resists increases of surface area; by gravity or foreign objects

water uses in life

• transport

• Medium in which chemical reactions of the metabolism take place

• solvent

adhesion

water attraction to polar/ charged materials

capillary action

• The ability of a liquid to move through narrow tubes that results from cohesion, adhesion and surface tension.

• Caused by adhesion of water molecules to surrounding materials.

• happens when adhesion is greater than cohesion

• is how water moves in the xylem

hydrophilic

molecules that are attracted to water, usually polar molecules

hydrophobic molecules

molecules why are not attracted chemically to water. Usually non polar molecules are like that

Aquaporins

Transmembrane proteins which are anchored in place on the plasma membrane by they hydrophobic exterior and hydrophilic interior. It allows for efficient transport of water in and out of the cell

Rules for dissolving

Like dissolves like; polar molecules dissolve polar molecules, and non polar molecules dissolve non polar molecules

Physical properties of water

• High buoyancy

• Low Viscosity

• High Thermal conductivity

• High Specific heat capacity

Buoyancy property

Counteracts gravity because of high density. Colder water is denser, so it sinks. Ice is less dense than water

Viscosity

How much energy is needed to change the shape of the liquid. Resistance to flow

Thermal conductivity

Ability of a substance to transfer heat when there is a temp difference. High thermal conductivity compared to other liquids ( which aren’t liquid metals ) : air has a much lower thermal conductivity than water

Specific heat capacity

How much energy is needed to raise the temperature of a substance. Water has a high one, higher than hydrogen, so a lot of energy is required to increase it’s temperature

Case study of seals

case study of black-throated loon ( bird)

goldilock zone

• area around a sun which allows for water to be liquid, thus for life to form

• it is also called the “habitable” zone

• other planets in such a zone might have the conditions for extraterrestrial life to emerge

origin of water on earth

collisions with water rich asteroids/ comets 4-5 billion years ago brought water on earth

why is water on earth

• temperate temperature: water doesnt evaporate nor it freezes, allowing it to be the ideal medium of life

• gravitational forces are strong enough to keep the water on earth’s surface