Water for life

Question 1

Why is water important?

Answer 1

most animals are 75-95% water
many live in water
most chemical reaction of life happen in water

Question 2

What are qualities of the water molecule?

Answer 2

Has two hydrogens and one oxygen

polar covalent bond(negative and positive charged ends)

Question 3

What end of the H2O molecule is negative?

Answer 3

Oxygen

Question 4

What are benefits of hydrogen bonds?

Answer 4

cause attraction between other water molecules, therefore, cohesion, adhesion, capillary action and surface tension

helps with thermal properties

Question 5

What are properties of hydrogen bonds?

Answer 5

weak bond if there are only a few
very strong if there are many
most stable in lattice form/solid (ICE)

Question 6

How do water molecules arrange themselves?

Answer 6

In tetrahedral formation

Question 7

What is cohesion?

Answer 7

the ability to stick to itself

Question 8

What is adhesion?

Answer 8

the ability to stick to other surfaces that are non-water polar or charged

Question 9

How can cohesion and adhesion work together?

Answer 9

capillary action and surface tension

Question 10

What is capillary action?

Answer 10

is when water sticks to itself in the xylem of a plant and using adhesion sticks to the side of the plant and climbs upward from roots to leaves

Question 11

What is surface tension?

Answer 11

when surface of water is strong enough to support insects/ lets droplets form (e.g. on leaves)

Question 12

What can you tell me about ice density?

Answer 12

Unusual as it is less dense than water

water freezes from top to bottom, therefore, organisms in lake will NOT FREEZE

hydrogen bonds are stable (not constantly breaking)

Question 13

How do you know that ice is less dense than liquid water?

Answer 13

BECAUSE IT FLOATS!!

Question 14

What are some properties of water?

Answer 14

High specific heat capacity
high vaporisation
good coolant

solvent
transport medium
metabolic react
diffusion

transparent

Question 15

What does ‘high specific heat capacity’ mean?

Answer 15

takes a lot of energy for temperature of water to change

due to numerous H bonds

Question 16

Why is it important that water is a good coolant?

Answer 16

high temps. = denatured proteins = death

because of high specific heat capacity water takes longer to heat and cool so when water evaporates it removes a lot of heat energy

Question 17

What is the benefit of water being transparent?

Answer 17

It can reach organisms on the sea floor

Question 18

What does ‘high vaporisation’ mean?

Answer 18

takes a lot of energy to evaporate

Question 19

How is water a good solvent?

Answer 19

Can dissolve many organic & inorganic substances

Can cause dissociation of ionic compounds bc. of H20 polar attraction

Question 20

Tell me about metabolic reaction?

Answer 20

happen most readily in solutions of water - water in cells dissolves reactants & substrates

Question 21

How does metabolic reaction affect diffusion?

Answer 21

since cells are mainly water, therefore, diffusion is easier if substance concerned is in solution

e.g. oxygen from alveoli to blood

Question 22

How is water a good transport medium?

Answer 22

because of metabolic reaction and diffusion, once the needed substance is diffused in cell that cell can then travel the body or plant to reach it’s destination and diffuse there

E.g. sucrose in plants, nutrients, waste products, circulatory system

Question 23

What is the definition of hydrophobic?

Answer 23

afraid of water
a substance that does not combine with water
always non-polar substance
e.g. oil

Question 24

What is the definition of hydrophilic?

Answer 24

water loving

a substance that is chemically attracted to water
always polar molecules/ positive & negative ions

e.g. glucose, cellulose

Question 25

How does water compare to CH4 (methane) ?

Answer 25

molecular mass - 16 v. 18
polarity - non v. polar
density (g cm-3) - 0.46 v. 1
specific heat capacity (J g-1) 2.2 v. 4.2
heat of vaporisation - 760 v. 2257
melting point - 182 v. 0
boiling point - -160 v. 100