▪️🔹1.1 Water -chemical elements and biological compounds Flashcards
What % of each individual human is water
70%
What kind of molecule is a water
A dipole
What does the term dipole mean?
It has a positively charged and negatively charged end with no overall change, there is 2 separations of charge in this ‘polar molecule’
How strong is an individual hydrogen bond?
Weak
When do hydrogen bonds become strong
In water when there is a large number of them as the molecules difficult to separate
What is a hydrogen bond?
The weak attractive force between the partial positive chars of a hydrogen atom of one molecule and a patk negative charge of an oxygen atom
Why is water an excellent solvent?
Because the water molecules are dipoles they attract charged particles and other polar molecules. These dissolve in water so chemical reactions take place in solution
What is hydrolysis?
Where water splits a molecule
Give an example of hydrolysis
Maltose + water -> glucose + glucose
What happens in a condensation reaction?
A chemical reaction occurs so that water is a product
Give an example of a condensation reaction
Glucose + fructose -> sucrose + water
How do water molecules arrange themselves in a solution?
Around other ions (e.g Na+ or Cl- ) in a solution
Ion in the middle and water molecules around its circumference
Name an example where water is used in biochemical reactions as a reactant
Carbon dioxide + water —> glucose + oxygen
What does water having a high specific heat capacity mean?
A large amount of heat energy is needed to raise its temperature
Name the structural reason why water has a High specific heat capacity
Because the hydrogen bonds between water molecules restrict their movement, resisting an increase In kinetic energy
What does waters high specific heat capacity prevent?
What does this mean?
It prevents large fluctuations in water temperature
- keeps aquatic habitats stable as organisms don’t need to adapt to extremes of temperature
- allows enzymes within cells to work efficiently
What does water having a high latent heat of vaporisation mean?
A lot of heat energy is needed to change water from a liquid to a vapour
Why is water having a High latent heat of vaporisation so important?
In thermoregulation where heat is used to vaporise water from sweat on skin or on a leafs surface. As water evaporates the body cools
Benefit of high latent heat of vaporisation on habitats
-aquatic habitats rarely evaporate away because so much energy is needed to vaporise the water
What is cohesion?
It’s where water molecules attract each other forming hydrogen bonds which are weak individually but ‘stick together’ in a lattice to become strong.
This ‘sticking together’ is cohesion
Why is cohesion of water vital to organisms?
It allows columns of water to be drawn up xylem vessels in plants for example
Why is water having a high surface tension important?
Cohesion at the surface (of a pond etc) produces surface tension so that a body of an organism e.g pond skater is supported
What does the High density of water provide?
Support and buoyancy
Why is ice less dense than water?
Because in ice the hydrogen bond hold the molecules further apart than they are in a liquid (less concentration of water molecules) :: it floats
