2.2 WATER

Question 1

Hydrogen bonding

Answer 1

Water Ms are polar+ H bonds form between them

• Water M attraction= ‘H bond’
• Intermolecular force/not bond

• Force: H atom in 1 polar M is attracted to a slightly –ve atom of another polar covalent M

Question 2

cohesive

Answer 2

• Binding together 2 M of same type
• Water M cohere: stick to each other
• →Due to H bond
• Useful for water transport in plants
• Water suck through xylem at low P
• →Only if water M don’t separate

Question 3

adhesive

Answer 3

• H bonds form between water and other polar M= water sticks to them
• Useful in leaves: water adheres to cellulose M in cell walls
• If water evaporates from cell walls and is lost from the leaf via the network of air spaces, adhesive forces cause water to be drawn out of the nearest xylem
• Keeps walls moist: so that they can absorb CO2 needed for photosynthesis

Question 4

PROPERTIES OF WATER

Answer 4

Hydrogen bonding + dipolarity explain water’s cohesive, adhesive, thermal and solvent properties

Question 5

solvent

Answer 5

• Polar nature of water M forms shells around charged/polar M prevents clumping/keep in solution
• Water forms H bonds with polar M
• Partial –ve O2 pole→+ve ions
• Partial +ve H pole→-ve ions: both dissolve
• Cytoplasm is a complex mixture of dissolved subs

Question 6

WATER THERMAL

high specific heat capacity

Answer 6

High specific heat capacity
•	H bonds restrict motion of water M + increases in the T of water require H bonds to be broken
•	Q of E needed to raise water T: >
•	To cool down: water loses > E
•	Water T is stable: good habitat

Question 7

HYDROPHILIC/ HYDROPHOBIC

Answer 7

Subs can be hydrophilic/phobic

• Philic: attracted to water
• All subs that dissolve in H2O
• Polar M + particles: +/-ve
• Subs that water adhere to
• Phobic: insoluble in water yet dissolve in other solvent
• M with no -/+ ve charge
• Non polar M
• All lipids: fats + oils

Question 8

COOLING THE BODY WITH SWEAT

Answer 8

• Heat needed for evaporation of water in sweat is taken from tissue of skin: reducing their T
• Effective method as body has high latent heat of v.
• Hypothalamus (brain) controls sweat secretion
• Receptors monitor blood T/ sensory inputs
• Transpiration is evaporation loss of water from plant leaves: cooling effect for hot environments

Question 9

TRANSPORT IN BLOOD PLASMA overview

Answer 9

Methods of transport of subs in blood relative to their H20 solubility

Question 10

TRANSPORT IN BLOOD PLASMA

AMINO ACID

Answer 10

Amino Acid: both -/+ve charges→
soluble in water but solubility depends on the R group: some hydrophilic/phobic.
All A.A are soluble enough to be carried in blood plasma

Question 11

TRANSPORT IN BLOOD PLASMA

GLUCOSE

Answer 11

Glucose: freely soluble polar M carried dissolved in blood p.

Question 12

TRANSPORT IN BLOOD PLASMA

OXYGEN

Answer 12

O2: non-polar M w/ < size dissolves only sparingly in water
water becomes saturated with O2 at low conc.

Q (O2) that blood p carries is < to provide aerobic R→

sol: haemoglobin in RBC has binding sites for O2
+ > blood capacity of O2 transport

Question 13

TRANSPORT IN BLOOD PLASMA

FAT

Answer 13

Fat M: entirely non-polar, >02, insoluble in water. They are carried in blood inside lipoprotein complexes.

Question 14

TRANSPORT IN BLOOD PLASMA

CHOLESTEROL

Answer 14

Cholesterol: Hphobic M, apart form small philic region at 1 end. Not enough to dissolve so carried in lipoprotein complexes.

Question 15

comparing methane and water

Answer 15

Property Methane Water
Formula CH4 H20
Molecular Mass 16 18
Density g/cm3 0.46 1
Specific heat capacity J/g/*C 2.2 4.2
Latent vaporization heat J/g 760 2,257
Melting point *C -182 0
Boiling Point -160 100

Question 16

comparing methane and water overview

Answer 16

Both < M with atoms linked by single covalent bonds
Water M are polar: form H bonds
CH4: non-polar: no H bonds

Question 17

water covalent bonds

Answer 17

• Water M: covalent bond- O & 2H+
• Unequal sharing of e- →polar covalent bond
• Nucleus of O > attractive to E
• Partial +ve change H+/-ve O
• Bent not linear
• +ve ions & -ve ions= ionic bonds

Question 18

WATER THERMAL

Answer 18

high specific heat capacity

high latent heat of vaporization

high boiling point

Question 19

WATER THERMAL

high latent heat of vaporization

Answer 19

• When a M evap is separates from other M in a liquid → vapour M
• Heat needed= L.H.O.V
• Evaporation has cooling effect
• > E/heat: break bonds: good coolant

Question 20

WATER THERMAL

high boiling point

Answer 20

• Liquid over a broad range of T 0-100

* > E /heat: break bonds→ habitats

Question 21

TRANSPORT IN BLOOD PLASMA

NaCl

Answer 21

NaCl: freely soluble ionic compound, dissolving to form Na+ ions + Cl- ions→ carried in blood plasma