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WJE
C G
CE B
IOLO
GY
Pro
pert
ies
of
Wate
r
Density
SurfaceTension
Cohesion
Colour
State atroomtemp.
Latentheat
Specificheat
capacity
Next
WJE
C G
CE B
IOLO
GY
Pro
pert
ies
of
Wate
r
Match the property of water with the corresponding significance for life and correctly fill in the table
START
WJE
C G
CE B
IOLO
GY
Pro
pert
ies
of
Wate
rProperty of water
Ice is less dense than water
High surface tension
Strong cohesive properties and high tensile strength
Colourless with a high transmission
Liquid at room temperature
In order to evaporate it must absorb a large amount of energy (high latent heat of vaporisation)
Water can absorb a lot of energy for only a small rise in temperature (high specific heat capacity)
Significance for life
Conditions are stable in cells and aquatic environments
Can be used for cooling organisms by evaporation of for example sweat
The high surface tension of water means that it can form a habitat on the surface of the water
Ice forms an insulating layer over water
Can be used for transport and a medium for reactions
Light can pass through cells for photosynthesis
Water can be pulled through plants in a column as the water molecules are held together by H-bonds
Answers
WJE
C G
CE B
IOLO
GY
Pro
pert
ies
of
Wate
rProperty of water
Ice is less dense than water
High surface tension
Strong cohesive properties and high tensile strength
Colourless with a high transmission
Liquid at room temperature
In order to evaporate it must absorb a large amount of energy (high latent heat of vaporisation)
Water can absorb a lot of energy for only a small rise in temperature (high specific heat capacity)
Significance for life
Conditions are stable in cells and aquatic environments
Can be used for cooling organisms by evaporation of for example sweat
The high surface tension of water means that it can form a habitat on the surface of the water
Ice forms an insulating layer over water
Can be used for transport and a medium for reactions
Light can pass through cells for photosynthesis
Water can be pulled through plants in a column as the water molecules are held together by H-bonds
Next
WJE
C G
CE B
IOLO
GY
Pro
pert
ies
of
Wate
rSurface 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
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WJE
C G
CE B
IOLO
GY
Pro
pert
ies
of
Wate
rColour – 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 53%
10%13%
9%
32%8%7%
7%
Reflected by leaves
Transmitted through leaves
Sun light
Light absorbed by leaves (typical values):
Near IR 15%
Red 82%
Green 80%
Blue 84% BackBack
WJE
C G
CE B
IOLO
GY
Pro
pert
ies
of
Wate
rCohesion
• Water molecules show a strong attraction to one another, this is called cohesion.
Droplets of water form spheres due to cohesion between water molecules
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WJE
C G
CE B
IOLO
GY
Pro
pert
ies
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Wate
rLatent 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.
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temperature
time
SOLI
D
LIQ
UID
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.
WJE
C G
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IOLO
GY
Pro
pert
ies
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Wate
rState at room temperature
• Water is a liquid at room temperature. However, all other similar molecules are gases.
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• 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
WJE
C G
CE B
IOLO
GY
Pro
pert
ies
of
Wate
rSpecific Heat Capacity
• The heat needed to raise the temperature of 1kg of water by 1°C is termed the Specific Heat Capacity.
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1kg of water
• Water has a large specific heat capacity, and therefore can absorb large amounts of heat energy before its temperature raises a significant amount.
thermometer
WJE
C G
CE B
IOLO
GY
Pro
pert
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of
Wate
rDensity of water
• Unlike other substances, water expands as it freezes.
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• 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.
Water molecules are able to approach one another quite closely
H H
O
H H
OH H
OH H
O
H H
O
H H
O
H H
O
H H
O
H H
O
H H
O
H H
O
Water molecules in ice form a rigid structure so that there is more space between them, this is seen as expansion as a wholeWater
Ice