Water

Question 1

how are atoms bonded in water

Answer 1

Covalent bonds

Question 2

Why is water a polar molecule

Answer 2

The oxygen atom attracts the electrons more strongly than the hydrogen atoms, resulting in a weak negatively charged region on the oxygen atom (δ-) and a weak positively charged region on the hydrogen atoms(δ+), this also results in the asymmetrical shape

Question 3

How are hydrogen bonds formed

Answer 3

the polar water molecules interact as the + and - regions of the molecule attract each other and from hydrogen bonds

Question 4

Hydrogen bonds characteristics

Answer 4

• weak + constantly breaking and reforming
• when there’s a lot of them they form a strong structure

Question 5

Characteristics of water (8)

Answer 5

solvent
• cohesive
• adhesive
• has surface tension
• high SHC
• high latent heat of vaporisation
• density
• colourless/ transparent

Question 6

Why’s water a good solvent

Answer 6

• water molecules are polar
• enables water molecules to attract solute molecules

Question 7

Why’s water being a good solvent significant for life

Answer 7

allows chemical reactions to occur within cells - as the dissolved solutes are more chemically reactive when they are free to move about
• polar molecules (amino acids, nucleic acids) can dissolve in the cytosol
• Metabolites// solutes can be transported efficiently in and out of cells

Question 8

Cohesion

Answer 8

Hydrogen bonds pull molecules towards each other // moves as one mass as molecules are attracted to each other

Question 9

Importance of surface tension

Answer 9

surface tension is strong enough for some insects e.g., Pond skaters to inhabit

Question 10

Adhesion

Answer 10

water molecules can be attracted to surfaces such as narrow tubes

Question 11

Specific heat capacity

Answer 11

the amount of energy needed to raise the temperature by 1 degree Celsius of a 1kg substance, without changing state

Question 12

Why does water have high SHC

Answer 12

due to the many hydrogen bonds present in water.
• a relatively large amount of energy is required to raise its temperature

Question 13

SHC OF WATER

Answer 13

4200 J/kg°C

Question 14

Importance of water having high SHC

Answer 14

Important in habitats as provides a stable environment eg. for fish
• maintaining temperatures that are optimal for enzyme activity

Question 15

Latent heat of vaporisation

Answer 15

the amount of energy needed to change the state (liquid to gas, vice versa) of 1kg a substance without changing its temp

Question 16

Why does water have a high latent heat of vaporisation

Answer 16

takes a lot of thermal energy to break hydrogen bonds and a lot of energy to build them
o absorbs a large amount of heat before it turns into gas

Question 17

Importance
of water having high latent heat of vaporisation

Answer 17

• reduces evaporation from ocean
  • provides a cooling effect for living organisms, for example the transpiration from leaves or evaporation of water in sweat on the skin

Question 18

What’s more dense? Ice or water

Answer 18

Water

Question 19

Why’s ice less dense than water

Answer 19

due to the hydrogen bonds
• when water is cooled below 4 degrees Celsius, the hydrogen bonds fix the polar molecules slightly further apart than the average distance in liquid state,
• forming an open lattice which is less dense than liquid water

Question 20

Condensation reaction

Answer 20

Joining of two molecules with the elimination of a molecule of water

Question 21

Hydrolysis reaction

Answer 21

Breaking a chemical bond between two molecules + involves the use of a water molecule

Question 22

Benefit of ice being less dense than water IRL

Answer 22

• provides habitat for some species
• floating ice insulates water below
• allows aquatic animals to move

Question 23

Answer 23