2.2 Water

Question 1

What is water made up of?

Answer 1

Two hydrogen atoms covalently bonded to an oxygen atom

Question 2

What does covalent bonding involve with electrons?

Answer 2

The sharing of electrons

Question 3

What is different in water molecules that does not match a typical covalent bonding property?

Answer 3

Electrons are not equally shared between the atoms

Question 4

Which element in water attracts electrons more strongly and why?

Answer 4

Oxygen due to having a higher electronegativity

Question 5

What causes polarity in water molecules?

Answer 5

The shared electrons orbit closer to the oxygen atom than the hydrogen atoms

Question 6

Why is water described as being polar?

Answer 6

As it has a slight charge difference across the different poles of the molecule

Question 7

What is the charge of oxygen atoms?

Answer 7

Slightly negative

Question 8

What is the charge of hydrogen atoms?

Answer 8

Slightly positive

Question 9

What allows water to form weak associations with other polar molecules?

Answer 9

The charge difference across the molecule

Question 10

What will the slightly negative poles attract?

Answer 10

The slightly positive poles of other molecules

Question 11

What does a hydrogen atom form when it is attached to fluorine, oxygen or nitrogen of another molecule?

Answer 11

A hydrogen bond

Question 12

Why are hydrogen bonds relatively stronger than other polar associations?

Answer 12

Due to the high electronegativity of Fluorine, Oxygen and nitrogen

Question 13

What does the dipolarity of a water molecule enable?

Answer 13

To form polar associations with other charged molecules

Question 14

What bond can water form with other water molecules?

Answer 14

Hydrogen bonds

Question 15

What are the three distinct properties of water?

Answer 15

Thermal properties
Cohesive/adhesive properties
Solvent properties

Question 16

What gives water distinct properties not seen in other substances?

Answer 16

The intermolecular bonding between water molecules

Question 17

Explain the thermal property of water?

Answer 17

Water can absorb much heat before changing state

Question 18

What does water changing state require?

Answer 18

The breaking of hydrogen bonds and that needs the absorption of energy

Question 19

Explain cohesive/adhesive properties of water?

Answer 19

Water will stick to other water molecules and charged molecules

Question 20

What is cohesion?

Answer 20

When like molecules sticks together

Question 21

What is adhesion?

Answer 21

When dissimilar molecules stick together

Question 22

Explain solvent properties of water?

Answer 22

Water dissolves polar and ionic substances

Question 23

What does water form to draw materials apart?

Answer 23

Competing polar associations

Question 24

Why can water absorb significant amounts of heat before changing state?

Answer 24

Due to the hydrogen bonding between water molecules

Question 25

Why is water an excellent medium for living organisms?

Answer 25

It is relatively slow to change temperature and thus supports the maintenance of constant conditions

Question 26

Why does methane provide a good basis of comparison of water?

Answer 26

Due to the similarities in their structures

Question 27

What does methane and water have in common?

Answer 27

Comparable size and weight Comparable valence structures

Question 28

Where do the differences in thermal properties between water and methane come from?

Answer 28

Differences in polarity between the molecules

Question 29

Is methane polar or non polar?

Answer 29

Non polar

Question 30

What type of bonds can methane form between its molecules?

Answer 30

Weak dispersion forces

Question 31

What absorbs more heat before changing heat: methane or water?

Answer 31

Water

Question 32

Does methane or water have a higher melting and boiling point?

Answer 32

Water

Question 33

Does methane or water have a higher specific heat capacity?

Answer 33

Water

Question 34

Does methane or water have a higher heat of vaporisation?

Answer 34

Water

Question 35

Does methane of water have a higher heat of fusion?

Answer 35

Water

Question 36

What is a mechanism used by humans to cool down?

Answer 36

The evaporation of water as sweat

Question 37

What does evaporation require?

Answer 37

An input of energy

Question 38

Where does the energy needed for evaporation for sweat come from?

Answer 38

The surface of the the skin when it is hot

Question 39

What happens to the skin when sweat evaporates?

Answer 39

It cools

Question 40

Because water is polar it will be attracted to other molecules that are...

Answer 40

Polar or have an iconic charge

Question 41

Why does water absorb a lot of thermal energy before it evaporates?

Answer 41

Because it has a high specific heat capacity

Question 42

What will water form with polar and charged molecules?

Answer 42

Intermolecular associations

Question 44

What explains waters surface tension?

Answer 44

Its cohesive properties

Question 45

What does hydrogen bonding between water molecules allow?

Answer 45

The liquid to resist low levels of external force

Question 46

What allows water to flow in opposition to gravity?

Answer 46

Attraction to charged or polar surfaces

Question 46

What explains waters capillary action?

Answer 46

Its adhesive properties

Question 46

What makes water suitable for smaller organisms to move along its surface?

Answer 46

Its high surface tension which makes it sufficiently dense

Question 47

Why is capillary action necessary?

Answer 47

To allow water to be transported up plant stems via a transpiration stream

Question 48

Why is water often referred to as the universal solvent?

Answer 48

Due to its capability to dissolve a large number of substances

Question 49

What can water dissolve?

Answer 49

Any substance that contains charged particles or electronegative atoms

Question 50

Why can water dissolve substances?

Answer 50

Because the polar attraction of the large amounts of water molecules can weaken intramolecular forces which causes the dissociation of the atoms

Question 51

What forms dispersive hydration shells?

Answer 51

The slightly charged regions of the water molecule surround atoms of opposing charge

Question 52

What are hydrophilic substances?

Answer 52

Substances that freely associate and readily dissolve in water

Question 53

What are examples of hydrophilic substances?

Answer 53

All polar molecules and ions

Question 54

What are hydrophobic substances?

Answer 54

Substances that do not freely associate or dissolve in water

Question 55

What are examples of hydrophobic substances?

Answer 55

Large, non polar molecules

Question 56

What does the transport of essential molecules within the bloodstream depend on?

Answer 56

Their solubility in water

Question 57

What is the difference in water soluble and water insoluble substances when they travel in the blood plasma?

Answer 57

Water soluble substances can move freely but water insoluble substances cannot

Question 58

What are four water soluble substances?

Answer 58

Sodium chloride Oxygen Glucose Amino acids

Question 59

Why can sodium chloride transport freely in blood?

Answer 59

It is an ionic compound

Question 60

Is oxygen soluble?

Answer 60

Yes but in low amounts

Question 61

How does most oxygen travel in the blood?

Answer 61

By haemoglobin within red blood cells

Question 62

Why can glucose travel freely in blood?

Answer 62

As it has many hydroxyl groups which can associate with water

Question 63

What state must amino acids be in for them to be transported in the blood?

Answer 63

An ionized state

Question 64

Why won't lipid dissolve in water?

Answer 64

Because they are non polar and hydrophobic

Question 65

How do lipids move through the bloodstream?

Answer 65

By forming complexes with proteins called lipoproteins

Question 66

What direction does the hydrophilic portions of proteins, cholesterol and phospholipids face and why?

Answer 66

Outwards to shield the the internal hydrophobic components