Water

Question 1

what is a hydrogen bond

Answer 1

a weak interaction that occurs when molecules contain a slightly negatively charged atom bonded to a slightly positively charged hydrogen atom

Question 2

which bonds are hydrogen bonds weaker than

Answer 2

covalent bonds

Question 3

how many hydrogen bonds form in polymers

Answer 3

thousands and thousands

Question 4

how is having many hydrogen bonds beneficial

Answer 4

it helps stablisise the structure of some biological molecules

Question 5

what atoms do water consist of

Answer 5

two hydrogen atoms covalently bonded to one oxygen atom

Question 6

why is the oxygen atom slightly negative

Answer 6

oxygen atoms have a greater number of positive protons in its nucleus which exerts a stronger attraction for shared electrons

Question 7

if oxygen is slightly negative, what does that make hydrogen

Answer 7

slightly positive

Question 8

what type of molecule is water

Answer 8

polar molecule

Question 9

what is specific heat capacity

Answer 9

the amount of energy required to raise one kg of a material by 1 degrees celsius

Question 10

what is specific latent heat

Answer 10

the amount of energy required to change the state of one kg of a material without changing its temperature

Question 11

what are the functions of water

Answer 11

• it is a good solvent
• reactant
• can make a good habitat
• controls temperature
• transport medium

Question 12

describe the polarity of water

Answer 12

shared electrons of covalent bond are more strongly attracted to the oxygen atom which makes the molecule have a slight negative charge on the oxygen atom and a slight positive charge on the hydrogen atom

Question 13

what can interact with water as a result of its polarity

Answer 13

other polarised molecules can interact with water and dissolve. this also includes ionic solutes

Question 14

how do substances dissolve in water

Answer 14

because water is polar, positive and negative parts of the water molecule are attracted to the negative and positive parts of the solute. water molecules cluster around these charged parts of the solute molecules and will help separate them and keep them apart. they dissolve to form a solution.

Question 15

are hydroxyls (-OH) polar or non polar

Answer 15

polar

Question 16

where do non polar solutes dissolve in

Answer 16

non polar solvents

Question 17

how is water being a good solvent beneficial for organisms

Answer 17

• molecules and ions can move around and react together in water. many such reactions happen in cytoplasm as it is 70% water.
• molecules and ions can be transported around living things whilst being dissolved in water

Question 18

why does ice float on water

Answer 18

in a liquid state, water molecules are closely held together by weak hydrogen bonds. on reaching a solid state, hydrogen bonds become stable arraning water molecules far apart from each other. this causes ice to have lesser density than water so it floats

Question 19

how is ice less denser than water

Answer 19

water becomes less dense when frozen but becomes more dense as it gets colder until about 4 degrees. as it goes from 4 degrees to freezing point, water molecules align themselves in a structure which is less dense than water

Question 20

how does the density of water provide an ideal habitat for living things

Answer 20

• aquatic organism have a stable environment in which to live throughout the winter.
• ponds and other bodies of water are insulated against extreme cold.
• the layer of ice reduces the rate of heat loss from the rest of the pond which insulates the water beneath

Question 21

what happens when water molecules constantly move around

Answer 21

they continually move and break hydrogen bonds

Question 22

what do the hydrogen bonds make difficult for the water molecules

Answer 22

for them to escape and become a gas

Question 23

does water have a high or low viscosity

Answer 23

low viscosity (flows very easily)

Question 24

what can water provide because of its viscosity

Answer 24

• it provides habitats
  -form major componenet of tissues in living organisms,
  -provide reaction medium for chemical reactions,
• provide a transport medium

Question 25

how is water adhesive

Answer 25

it has a tendency for the water molecules to stick to other substances

Question 26

how is water cohesive

Answer 26

it has a tendency for water molecules to stick to each other

Question 27

why is water cohesive

Answer 27

the hydrogen bonds between the molecules pulls them together

Question 28

where else does cohesion happen

Answer 28

at the surface of the water. water molecules at the surface are all hydrogen bonded to molecules beneath. they are more attracted to water molecules beneath than to air molecules above. this causes the surface of water to contract (molecules are pulled inwards)

Question 29

what is surface tension

Answer 29

the surface of water has the ability to resist force applied to it.

Question 30

what are the advantages of cohesion, adhesion and surface tension

Answer 30

• columns of water in plant vascular tissue are pulled up the xylem tissue from the roots
• insects such as pond skaters can walk on water

Question 31

does water have a high or low specific heat capacity

Answer 31

high specific heat capacity

Question 32

how many joules of energy are required to raise 1kg of water by 1 degrees Celsius

Answer 32

4200kJ

Question 33

why does water have a high specific heat capacity

Answer 33

water temperature is a measure of the kinetic energy of water molecules. water molecules are held together quite tightly by hydrogen bonds so you have to put a lot of heat energy to increase the kinetic energy and therefore the temperature

Question 34

what is the advantage of water having a high shc

Answer 34

water doesnt fluctuate in temperature which makes it stable for living things. it is good for enzyme controlled reactions and creates a stable environment for aquatic organism

Question 35

why is water considered to be a coolant

Answer 35

because of its high latent heat of vaporisation, water cools living things and keeps the temperature stable

Question 36

why does water have a high specific latent heat of vaporisation

Answer 36

molecules of water are held together by hydrogen bonds so a large amount of energy is needed for water molecules to evaporate

Question 37

why is water being a reactant important

Answer 37

it is important for the digestion and synthesis of large biological molecules