properties of water Flashcards
how these properties are significant for life
ice is less dense than water
ice forms an insulating layer over water
high surface tension
the high surface tension of water means that it can form a habitat on the surface of the water
strong cohesive properties and high tensile strength
water can be pulled through plants in column as the water molecules are held together by H-bonds
colourless with a high transmission
light can pass through cells for photosynthesis
liquid at room temperature
can be used for transport and a medium for reactions
in order to evaporate it must absorb a large amount of energy (high latent heat of vaporisation)
can be used for cooing organisms by evaporation of for example sweat
water can absorb a lot of energy for only a small rise in temperature (high specific heat capacity)
conditions are stable in cells and aquatic environments
surface tension
The surface of water can behave like an elastic sheet • The molecules in the bulk of the liquid are effected by various intermolecular forces of attraction • Those molecules in the surface are not effected by molecules above them, and therefore ‘pull’ together more strongly, effectively resembling a stretched membrane • A habitat can therefore survive on the surface of the water
colour- transmission of light
Water is colourless and is therefore transparent to light • This means that sunlight can reach the cells and pass through them so that photosynthesis may occur
Light absorbed by leaves (typical values): Near IR 15% Red 82% Green 80% Blue 84%
Reflected by leaves 53% 10% 13% 9%
Transmitted through leaves 32% 8% 7% 7%
cohesion
Water molecules show a strong attraction to one another, this is called cohesion. Droplets of water form spheres due to cohesion between water molecules
latent heat
While changing state, a substance will take in heat energy (solid liquid gas), or expel heat energy (gas liquid solid) without a change in temperature. This is termed Latent Heat. Back temperature time GAS melt solidify evaporate condense • Water has a large latent heat of vaporisation, and therefore absorbs a large amount of heat energy while changing from water to vapour.
state at room temperature
Water is a liquid at room temperature. However, all other similar molecules are gases. Back • Hydrogen bonds act between the water molecules, and they attract them enough so that it behaves as a liquid. H H O + + 2- H H O + + 2- H H O + + 2- H H O + + 2- Hydrogen bonds form because of polar covalent bonding between the oxygen and hydrogen atoms
specific heat capacity
The heat needed to raise the
temperature of 1kg of water by 1°C is
termed the Specific Heat Capacity.
Water has a large specific heat capacity, and therefore can absorb large amounts of heat energy before its temperature raises a significant amount.
density of water
Unlike other substances, water expands
as it freezes.
Water molecules are able to
approach one another quite closely.
Water molecules in ice form a rigid structure so that there is more space between them, this is seen as expansion as a whole.
As water expands when it freezes, its density (mass per unit volume) will decrease. • This means that ice is less dense than water, and will therefore float on top of it.
inorganic ions: how are minerals described
-minerals are described as micronutrients and macronutrients
