Water

Question 1

What is the bond that links two water molecules together?

Answer 1

Hydrogen bond

Question 2

Define the term polar

Answer 2

Electrons are not shared equally over a covalent bond and the atoms have small partial charges as a result of this

Question 3

What is a dipole?

Answer 3

The partial charges on atoms in a covalent bond

Question 4

What is electronegativity?

Answer 4

A measure of an atom’s ability to attract shared electrons to itself

Question 5

Why does the polar nature of water mean it is a solvent?

Answer 5

Positive and negative ends of water molecules are attracted to ions, allowing them to dissolve

Question 6

Why does the polar nature of water mean it is a transport medium?

Answer 6

It can form hydrogen bonds with other polar molecules or charged ionic compound

Question 7

Why does the polar nature of water mean it is a coolant?

Answer 7

Water forms many hydrogen bonds which take a lot energy to break

Question 8

Why does the polar nature of water mean it is a reactant?

Answer 8

Allows it to form many covalent bonds with substances

Question 9

How does water having a high specific heat capacity make it support life?

Answer 9

Stable environment for aquatic organisms
Thermoregulation
Stable temperature for enzyme controlled reactions
Cells less prone to damage

Question 10

Why does water having a high latent heat of vapourisation make it support life?

Answer 10

Makes it a coolant - so it stays liquid over a range of temps so it is a stable environment for aquatic organisms

Question 11

Why does water being cohesive make it support life?

Answer 11

Allows for the transpiration stream?
Surface tension - provides habitiat on surface of water for organisms such as pond skaters

Question 12

Why does water being a universal solvent make it support life?

Answer 12

Transport medium
Hydrolysis reactant
Reaction medium
Main component of cells as solutes tend to be polar/charged

Question 13

Why does water being adhesive make it support life?

Answer 13

Allows for transpiration due to attraction to xylem wall

Question 14

Why does water being a low density solid make it support life?

Answer 14

Ice floats on water creating a habitat on top for terrestrial organisms and insulates water below from cold air providing a habitat for aqueous organisms
Water is most dense at 4C so when it sinks it creates circulating nutrient currents

Question 15

Define hydrophilic

Answer 15

Polar molecule that is attracted to water molecules and tends to be dissolved by water

Question 16

Define hydrophobic

Answer 16

Non-polar molecule that is not attracted to water molecules and does not dissolve in water

Question 17

Define cohesion

Answer 17

Attraction to molecules of the same kind

Question 18

What is adhesion?

Answer 18

Attraction to other substances

Question 19

What are the ‘other’ properties of water that are not due to its polar nature?

Answer 19

Helps in sexual reproduction - sperm swim within water for external fertilisation and semen made of water otherwise
Support - makes plant cells turgid so supports them, hydrostatic skeleton in some living organisms
Lubricant - helps bones to move over each other without damage

Question 20

Why is water a polar molecule?

Answer 20

It has an unequal sharing of electrons because the electrons are more attracted to oxygen as it has more protons

Question 21

Which part of a water molecule is delta negative and which part is delta positive?

Answer 21

Delta negative - oxygen
Delta positive - hydrogens

Question 22

How do hydrogen bonds form between water molecules?

Answer 22

Adjacent water molecules align themselves to be attracted to the molecule next to them as they turn their oxygen sides away from each other

Question 23

What is the bond that holds oxygen and hydrogen atoms together within a water molecule?

Answer 23

Polar covalent bond