IB Biology(HL)--- Water

Unit 1.1 --- 1.3

Enzymes

Biological molecules that increase the rate of chemical reactions and need to be dissolved in water to function.

Water(general)

Provides a chemically stable medium for all processes of life to function.

H2O Molecule

Possesses an unequally distributed electrical charge due to the net negative charge on oxygen and net positive charge on hydrogen.

Hydrogen Bonding

The attraction between positively charged hydrogen atoms of one water molecule and negatively charged oxygen atoms of another, responsible for holding water molecules together.

Covalent Bond

A chemical bond that involves the sharing of electrons to form electron pairs between atoms

Cohesive Forces

Allow water molecules to be drawn up xylem vessels in plants due to strong cohesive properties.

Surface Tension

Water's strong surface tension allows it to form almost spherical droplets due to hydrogen bonding at the surface.

Evaporative Cooling

A mechanism that helps regulate temperature in living organisms by cooling the surface as liquid evaporates.

Density

The ratio of mass to volume of a substance; ice is less dense than liquid water due to its crystalline structure.

Buoyancy

The tendency of an object to float in a fluid; objects float in water when their density is less than that of water.

Specific Heat Capacity

The amount of heat required to raise the temperature of one gram of a substance by one degree Celsius; water has a high specific heat capacity.

Viscosity

The resistance to flow; water has lower viscosity than air, allowing easier movement of organisms like birds.

Capillary Action

The ability of water to move up against gravity in narrow tubes due to adhesion and cohesion.

Hydrophilic Substances

Substances that dissolve in water due to their polarity being stronger than water's cohesive forces.

Hydrophobic Substances

Substances that are repelled by water due to lacking charged poles.

Thermal Conductivity

The ability of a substance to conduct heat without the movement of the material itself.

Adhesion

The force by which individual molecules stick to surrounding materials and surfaces.

Heat of Vaporization

The amount of energy needed to change 1g of liquid into gas.

Solvent

A liquid in which another substance can be dissolved.

Solute

A dissolved molecule or ion in a solution.

Cohesion

A force by which individual molecules of the same type/substance attract or associate(“stick together”)