water

Question 1

describe the structure of water

Answer 1

• 2 hydrogen and 1 oxygen molecule
• hydrogen is slightly positive charge
• oxygen has a slightly negative charge
• this makes water dipolar (2 polar regions)
• this creates weak hydrogen bonds between the molecules

Question 2

what are hydrogen bonds and what can they link together

Answer 2

• weak bonds that join a slightly positive hydrogen bond to a slightly positive molecule
• causes water molecules to stick together

Question 3

define polar

Answer 3

molecule with charged regions

Question 4

list the roles water plays in life

Answer 4

• solvent - molecules can be dissolved for transportation
• cohesion and adhesion - transpiration stream
• high specific heat capacity - takes a lot of energy to break hydrogen bonds - stable environment
• ice less dense than water - floats, insulation the water below
• transparent :photosynthesis possible for aquatic organisms
• surface tension - habitat for invertebrates

Question 5

explain why water is an effective transport medium, coolant, reactant and habitat
- due to polarity

Answer 5

transport medium:
polarity means solvent. molecules can be dissolved
coolant:
polarity means hydrogen bonds. hard to break so resists temp. change
reactant:
polarity = charges = reactivity
habitat:
ice is less dense due to hydrogen bonds. insulates water below.

Question 6

define hydrophilic and hydrophobic

Answer 6

philic:
associates with water molecules easily

phobic:
repels water molecules

Question 7

define cohesion and adhesion:

Answer 7

cohesion: attraction between molecules due to hydrogen bonding
adhesion: attraction between molecules of different substances

Question 8

explain how water can ‘dome’

Answer 8

• top layer of molecules forms a skin:
• non polar air molecules do not bond with polar water molecules
• only bonds are sideways and downwards
• water molecule pulled downwards
• surface tension is created