Water

Question 1

Describe the structure of a water molecule

Answer 1

An oxygen atom covalently bonded to two hydrogen atoms, with a non linear shape.

Question 2

What is the bond that links two water molecules together

Answer 2

A hydrogen bond

Question 3

What is a hydrogen bond

Answer 3

A hydrogen bond is a weak interaction between the slightly negative oxygen of one water molecule and the slightly positive hydrogen of another.

Question 4

Define the term polar

Answer 4

Opposite slight charges on two sides of a molecule, one slightly positive and one slightly negative

Question 5

Explain why a water molecule is polar

Answer 5

Water is a polar molecule as the oxygen is more electronegative so attracts the shared pair of electrons more strongly than the hydrogen making the oxygen slightly negative and the hydrogen slightly positive

Question 6

Define electronegativity and dipole

Answer 6

electronegativity = tendency for an atom to attract a bonding pair of electrons 
dipole = a molecule in which the concentration of positive charge is separated from a concentration of negative charge

Question 7

list 5 roles water plays in life

Answer 7

transport medium 
solvent 
coolant 
reactant 
habitat

Question 8

Explain how the polar nature of water allows it to be a transport medium, solvent, coolant, reactant and habitat

Answer 8

TRANSPORT MEDIUM - liquid over large range of temps, can dissolve many materials.
SOLVENT- dissolves polar and charged molecules as polar water molecule cluster around them, keeping them apart
COOLANT - high specific heat capacity - H bonds require a lot of energy to overcome
HABITAT - maintains constant temp as H bonds require a lot of energy to overcome

Question 9

define hydrophilic and hydrophobic

Answer 9

hydrophilic - physical property of a molecule that is attracted to water
hydrophobic - physical property of a molecule that is repelled by water

Question 10

define cohesion and adhesion

Answer 10

cohesion - water molecules attracted to other water molecules
adhesion - water molecules attracted to other substances

Question 11

describe any other properties of water that makes it useful for life

Answer 11

transparent to light so plants under water can get light for photosynthesis and aquatic animals can see

Question 12

examples of how water is used across the whole diversity of life

Answer 12

support - hydrostatic skeleton of earthworms and turgidity in plants
lubrication - synovial joints such as elbow have a sac of synovial fluid which stops bones rubbing against each other
buoyancy - wales couldn’t be as big
swimming - when something pushes against water there is an equal repelling force pulling forward
reactions - photosynthesis, hydrolysis reactions
high surface tension - organisms can suspend themselves on the surface - pond skaters
ice floats - so floats so organisms underneath can live
regulating reaction and conditions - sweating and high specific heat capacity

Question 13

using the polar nature of water explain how it can dome above the level of the glass container, make the shape of a meniscus and capillary action

Answer 13

dome - cohesion between water molecules causes surface tension due to H bonds
meniscus - adhesion to sides of container draws water molecules up
capillary action - cohesion to water and adhesion to other molecules explains how water moves up narrow spaces - important in xylem