A1.1 Water Flashcards
Why is water important?
It’s essential for life:
- Universal solvent
- Where biochemical reactions can take place
- Where most organisms live
- Most organisms have a high water content
What gives water molecules special properties?
Their polarity:
- the oxygen in water has a bigger nucleus which attracts more electrons
- this causes an unequal distribution of charge within the molecule
- overall charge is zero but the molecule has ‘poles’
What are the bonds formed in and between a water molecule?
In: Covalent bonds
Between: Hydrogen bonds (due to the polarity of water and the electromagnetic attraction between molecules)
How many bonds can be formed between water molecules?
4 H-bonds per water molecule
What special properties does water have due to its polarity? What do all of these special properties allow for?
- Cohesion
- Adhesion
- Solvency
- High specific heat
These properties allow water to be the main medium for life
Solvency:
what does/doesn’t water dissolve?
+ give some examples
Water is a universal solvent:
- it can dissolve polar molecules/ionic compounds (hydrophilic molecules) such as glucose and NaCl
- it can’t dissolve non-polar/non-charged molecules (hydrophobic molecules) such as cholesterol and fats
Solvency:
how does water’s solvent properties benefit organisms?
- most organisms have a high water content
- allows for transport of essential materials (amino acids, carbohydrates, minerals) around the body
- usually transported through blood - allows for biochemical reactions to take place
- cytoplasm is made of mostly water
Cohesion:
What is cohesion?
Why does this happen?
What properties does it give water?
- water sticks to itself
- it forms h-bonds between water molecules
- resists the increase of surface area and can counteract/resist gravity
Cohesion:
Why is cohesion beneficial to animals?
- allows animals to transport water through cells and tissue (transpiration)
- creates surface tension which is used by small insects to walk on the surface of water (pond skaters)
- allows for capillary action as they stick together and climb up against gravity
Adhesion:
What is adhesion?
Why does this happen?
What properties does it give water?
- water sticks to other polar/charged molecules
- water is polar so it can form h-bonds with other molecules
- on their own, bonds are weak but the more bonds the stronger they are
Adhesion:
Why is adhesion beneficial to animals?
- allows for capillary action as the water forms bonds with the xylem cell wall which pulls/sucks water up through the plant
Why is ice less dense?
How does this help animals?
The hydrogen bonds spread the molecules farther apart
It forms an ice layer over bodies of water that insulates the water underneath
Specific heat capacity
What is it?
Is it high or low for water?
What does this mean for animals?
Water has a high specific heat capacity
This means it takes a lot of energy to heat up water
This provides a stable environment for organisms, both in water habitats and inside their bodies
It allows for thermal regulation
Latent heat of vaporisation
What is it?
Is it high or low for water?
What does this mean for animals?
Water has a high latent heat of vapourisation
This means it takes a lot of energy for water to change state from liquid to gas
This means that animals can sweat to lose heat as it draws away heat from the body
Buoyancy
What is it?
What does this mean for animals?
Give specific examples
The ability for an object to stay afloat
or
the ability of a liquid to exert upward force on an object
things that are less dense than water will float
this helps animals minimise the energy expended trying to stay afloat
Loons trap air and oil in their feathers
Seals have a lot of blubber
Viscousity
What is it?
Is it high or low for water? Compared to air?
What does this mean for animals? How do they adapt? Give specific examples
A liquids resistance to movement
Water is more viscous than air
Harder to move through it so being aerodynamic is important
loons and seals are torpedo shaped
Thermal conductivity
What is it?
Is it high or low for water? Compared to air?
What does this mean for animals? How do they adapt? Give specific examples
ability to move heat across a temperarzre gradient
water is a good conductor
means you get colder in water and lose heat quickly
to prevent this:
- loon have oiled feathers that trap air and repel water which insulated them
- seals have thick layers of blubber that keep them insulated
Origin of water
Where did water come from?
Why does it stay on earth? What conditions does the earth have to allow this?
Scientists believe that a comet carrying ice hit the earth and brought water to it
Once the water was able to exist in a majority liquid state, life could begin
This temp was reached because Earth exists in the habitable/goldilocks zone
Gravity is what keeps the water from escaping
What properties do enzyme molecules have relating to water?
Enzymes are proteins and are carried in the blood, meaning they have to be hydrophilic and soluble.
How are fats transported in the body? Explain the structure?
- They are carried in blood inside lipoprotein complexes (in the plasma)
- Outer layer consists of single layer of phospholipid molecules:
- Hydrophilic phosphate heads of the phospholipids face outwards and are in contact with water
- Hydrophobic hydrocarbon tails face inwards and are in contact with the fats
- Proteins are also embedded in the phospholipid layer
State the property of water that causes water to be retained in soil by capillary action
explain how the physical properties of water support life in aquatic environments (with specific examples)
Outline the thermal, cohesive and solvent properties of water:
Thermal:
- water has a high specific heat capacity - takes a lot of energy to heat it up
- water has a high latent heat of vaporization - takes a lot of energy to vaporise it
Cohesive:
- hydrogen bonds between water molecules make them
cohesive/stick together;
- gives water a high surface tension
(explains how water rises
up xylem)
Solvent:
- water molecules are polar;
this makes water a good solvent;
Explain, with reference to its properties, the significance of water as a coolant, a means of transport and as a habitat.
Coolant:
- High specific heat capacity and latent heat of vaporisation
- When water evaporates energy is used and cools down organism;
- eg sweating / panting / transpiration;
Transport:
- water is polar and a universal solvent
- dissolves many organic and inorganic substances;
- water is adhesive and cohesive
- can transport vital nutrients and substances through xylem, blood, plasma etc
Habitat:
- water is transparent and allows for light photosynthesis
- Surface tension creates a habitat for surface creatures to live on
- contains dissolved gases fo fish and aquatic organisms survive under ice at surface;
- ice is less dense than liquid water and insulates bodies of water in the winter
Which physical property of water makes it an effective coolant?
High specific heat capacity
