water

Question 1

in water, which atom’s nucleus has electrons closer to it and why?

Answer 1

oxygen because it has more protons in the nucleus which means that there is a greater force of attraction between protons (in nucleus) and electrons(in shells)

Question 2

in water, what charge does the oxygen atom have?

Answer 2

slightly negative (s-)

Question 3

in water, what charge do the hydrogen atoms have?

Answer 3

slightly positive (s+)

Question 4

what is a hydrogen bond?

Answer 4

the electrostatic attraction between a slightly positive charge on the atom of one molecule and the slightly negative charge of a different atom

Question 5

which properties of water do we only need to know the basics for?

Answer 5

transparent
low viscosity(runny)
adhesion
non-compressible

Question 6

which properties of water are required to know at alevel?

Answer 6

cohesive
good solvent
metabolite
high specific heat capacity
high latent heat of vaporisation

Question 7

why does water have a high specific heat capacity?

Answer 7

• many hydrogen bonds between water molecules
  -lots of energy is needed to overcome these many bonds
  -this happens first before energy can be transferred to the actual water molecule to increase the kinetic energy and heat the water

Question 8

what is the phrase which says that water helps maintain a stable temperature which is an advantage for living things?

Answer 8

water buffers temperature changes

Question 9

why is water buffering temperature changes important for living things?

Answer 9

it keeps temp inside a living thing stable so provides the optimum temperature for reactions and enables thermoregulation

Question 10

what is specific heat capacity?

Answer 10

the amount of energy required to raise the temperature of one gram of a substance by one degree

Question 11

what is latent heat of vaporisation?

Answer 11

the amount of heat energy required to change the state of a substance from a liquid to a gas

Question 12

why is the latent heat of vaporisation of water high?

Answer 12

because a lot of energy is required to break the many hydrogen bonds between molecules

Question 13

what is sweat made from?

Answer 13

water and ions

Question 14

how is sweat able to evaporate?

Answer 14

water molecules absorb heat energy from the body. heat energy breaks the hydrogen bonds and the molecules have more kinetic energy so evaporate

Question 15

what is the benefit to living things that sweat?

Answer 15

evaporation of sweat has a large cooling effect- preventing rises in body temperature so enzymes don’t denature and chemical reactions occur at the optimum rate

Question 16

why does the evaporation of sweat have a large cooling effect?

Answer 16

a lot of energy is removed from the body in order to break the hydrogen bonds in the water molecules of sweat so it can evaporate

Question 17

what is a solvent?

Answer 17

a substance that can dissolve another substance (a solute)

Question 18

what are polar substances?

Answer 18

substances with a charge (positive or negative)

Question 19

what kind of polar is water and why?

Answer 19

dipolar because it has both a slightly positive and negative charge

Question 20

why can’t water dissolve lipids?

Answer 20

fats are non polar

Question 21

what are the two benefits or water being a good solvent for living things?

Answer 21

1. substances dissolved in water can be transported around the body/structure
2. it provides a medium for chemical reactions to take place (collisions=reactions)

Question 22

what is a metabolite?

Answer 22

a reactant or product of a metabolic reaction

Question 23

what is a condensation reaction?

Answer 23

a chemical reaction that joins two molecules to form a single molecule, releasing a smaller molecule (e.g. water)

Question 24

what is a hydrolysis reaction?

Answer 24

a reaction where a molecule of water breaks one or more chemical bonds

Question 25

what is cohesion of water?

Answer 25

one water molecule 'sticks' to the next via hydrogen bonding

Question 26

explain why water is cohesive?

Answer 26

hydrogen bonds form between water molecules due to the slightly positively charged hydrogen atoms of one molecule being attracted to the slightly negative charged oxygen atom of a second molecule

Question 27

explain why water is a good metabolite?

Answer 27

water can be a reactant in a chemical reaction because the bonds in the water molecule can break and the atoms can bond with other atoms- water can also be a product that is made in chemical reactions

Question 28

explain why water is a good solvent?

Answer 28

can dissolve polar substances because it too has polarity. For example, the s+ charge on the hydrogen atom allows water molecule to be attracted to s- charges. An ion would therefore become surrounded by water and be dissolved

Question 29

why is water buffering temperature changes important for aquatic organisms?

Answer 29

the temperature of water they live in does not change rapidly- temp more stable than air

Question 30

how can water having a high latent heat of vaporisation be important for plants?

Answer 30

transpiration of water (evaporation of water from leaves) cools plants

Question 31

why is water being cohesive important for xylem vessels?

Answer 31

water molecules can form a continuous column of water so mass flow can occur. If one water molecule moves then the other water molecules will flow with since they're joined via h bonds - therefore there can be bulk transport of substances down pressure gradients so mass flow of water from roots to leaves in xylem

Question 32

how does surface tension of water enable small animals to walk on the surface of water?

Answer 32

surface tension of water occurs because the top layers of water molecules do not have any water molecules above them to which they can be attracted - there is a net attraction downwards and surface tension produced supports body of an insect

Question 33

give an example of where water is used as a metabolite in a hydrolysis reaction?

Answer 33

ATP is hydrolysed to release the energy for the cell's activities

Question 34

give two examples of where water is used as a metabolite in a condensation reaction?

Answer 34

when amino acids are joined together to produce proteins join ADP and Pi to make ATP during respiration

Question 35

give examples of how substances dissolved in water can be transported?

Answer 35

blood plasma is mainly water and dissolved within this water are glucose, ions, carbon dioxide , urea etc; when blood flows these dissolved substances are transported plants transport dissolved substances in water of xylem.