▪️🔹1.1 Water -chemical elements and biological compounds

Question 1

What % of each individual human is water

Answer 1

70%

Question 2

What kind of molecule is a water

Answer 2

A dipole

Question 3

What does the term dipole mean?

Answer 3

It has a positively charged and negatively charged end with no overall change, there is 2 separations of charge in this ‘polar molecule’

Question 4

How strong is an individual hydrogen bond?

Answer 4

Weak

Question 5

When do hydrogen bonds become strong

Answer 5

In water when there is a large number of them as the molecules difficult to separate

Question 6

What is a hydrogen bond?

Answer 6

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

Question 7

Why is water an excellent solvent?

Answer 7

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

Question 8

What is hydrolysis?

Answer 8

Where water splits a molecule

Question 9

Give an example of hydrolysis

Answer 9

Maltose + water -> glucose + glucose

Question 10

What happens in a condensation reaction?

Answer 10

A chemical reaction occurs so that water is a product

Question 11

Give an example of a condensation reaction

Answer 11

Glucose + fructose -> sucrose + water

Question 12

How do water molecules arrange themselves in a solution?

Answer 12

Around other ions (e.g Na+ or Cl- ) in a solution

Ion in the middle and water molecules around its circumference

Question 13

Name an example where water is used in biochemical reactions as a reactant

Answer 13

Carbon dioxide + water —> glucose + oxygen

Question 14

What does water having a high specific heat capacity mean?

Answer 14

A large amount of heat energy is needed to raise its temperature

Question 15

Name the structural reason why water has a High specific heat capacity

Answer 15

Because the hydrogen bonds between water molecules restrict their movement, resisting an increase In kinetic energy

Question 16

What does waters high specific heat capacity prevent?

What does this mean?

Answer 16

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

Question 17

What does water having a high latent heat of vaporisation mean?

Answer 17

A lot of heat energy is needed to change water from a liquid to a vapour

Question 18

Why is water having a High latent heat of vaporisation so important?

Answer 18

In thermoregulation where heat is used to vaporise water from sweat on skin or on a leafs surface. As water evaporates the body cools

Question 19

Benefit of high latent heat of vaporisation on habitats

Answer 19

-aquatic habitats rarely evaporate away because so much energy is needed to vaporise the water

Question 20

What is cohesion?

Answer 20

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

Question 21

Why is cohesion of water vital to organisms?

Answer 21

It allows columns of water to be drawn up xylem vessels in plants for example

Question 22

Why is water having a high surface tension important?

Answer 22

Cohesion at the surface (of a pond etc) produces surface tension so that a body of an organism e.g pond skater is supported

Question 23

What does the High density of water provide?

Answer 23

Support and buoyancy

Question 24

Why is ice less dense than water?

Answer 24

Because in ice the hydrogen bond hold the molecules further apart than they are in a liquid (less concentration of water molecules) :: it floats

Question 25

Name the benefits of ice being less dense than water

Answer 25

It’s a good insulator that prevent large bodies of water losing heat and freezing completely so organisms beneath survive

Question 26

Name a benefit of water being transparent

Answer 26

It allows light to pas through which means aquatic plants can photosynthesise effectively

Question 27

Explain why water is able to dissolve in sodium chloride

Answer 27

Cl- ions attract partial positive charge of hydrogen atoms in water
Na+ ions attract negative dipole (o2- ions) in water

Question 28

What is meant by metabolic water?

Answer 28

Water produced from the oxidation of food during respiration.