A1.1 Water

Why are many substances easily dissolved in water

it is a solvent

what is the charge of the oxygen in a water molecule

slightly negative

what is the charge of a hydrogen in a water molecule

slightly positive

describe water's surface tension compared to other liquids

high

describe water's specific heat capacity compared to other substances

high

why is it important that water has a high specific heat capacity

it can stabilize the temperature of aquatic ecosystems and can help cool organisms through evaporation

give an example of how the solvent properties of water benefit living organisms

helps the transport of the vital compounds of life like nitrates and phosphates

why is water often called the universal solvent

It can dissolve many other molecules due to its polarity

what are hydrophilic substances

charged substances that mix and dissolbe in water

give an example of water being used as a transport medium in animals

nutrients, hormones, oxygen, CO2 and antibodies are all transported through the body in water

give an example of water being used as a transport medium in plants

ionic minerals are dissolved in water and travel up the plants in xylem, organic molecules are dissolved in water and are transported through the phloem

name three substances that are dissolved in blood plasma

glucose, amino acids, sodium chloride

what substance is attached to haemoglobin

oxygen

why doesn't oxygen readily dissolve in water

it is non-polar

what is the medium for metabolism

water

what is a simple definition of metabolism

the network of chemical reactions in living organisms

what are enzymes

biological catalysts made of proteins that speed up the rate of chemical reactions and are involved in controlling metabolism

what type of solutions do metabolic reactions occur in

aqueous solutions

describe hydrophobic substances

not charged, and do not readily mix with water

give an example of a hydrophobic molecule in the body

lipids

why is it important that lipids are hydrophobic

they can be used as an energy store without changing the water potential of cell, it also means they are able to pass through the phospholipid bilayer of cell membranes

What is buoyancy?

the upward force exerted by a fluid on an object immersed in the fluid

how does buoyancy help aquatic animals

it helps them conserve energy and stay afloat

what is viscocity

the thickness of a fluid or its resistance to flow

is water more or less viscous than air

more

why is waters thermal conductivity important to aquatic animals

they are more likely to lose heat to the environment so they must be adapted to reduce heat loss

what is specific heat capacity

the amount of energy required to raise the temperature of 1g of a substance by 1K or 1C

does water have a high or low specific heat capacity

high

why is unlikely that water was on earth when the planet was formed

temperatures would have been above 100C

how is it believed water arrived on earth

it was brought to earth by asteroid impacts, these asteroids are known as carbonaceous chondrites

how was water retained on earth

the distance of the earth from the sun means the sunlight never raises temperature high enough for water to boil, earth has a relatively strong gravitational pull which holds the water to earths surface

give some evidence for the asteroid theory for the presence of water on earth

earths oceans and asteroids have similar ratios of protium to deuterium so it can be assumed that they come from the same source

what does the goldilocks zone refer to

the habitable zone around a star where liquid water can exist on the planets surface

what does the location of a stars goldilocks zone depend on

the size of the star and the amount of energy it emits

what percentage (by mass) of most multicellular organisms is made up by water

65-95%

what is the charge of the oxygen atom in water

slightly negative

what is the charge of the hydrogen atoms in water

slightly positive

why is water known as polar

the water molecule has an unequal distribution of electrical charge within it

describe hydrogen bonding in water

the positively charged hydrogen atoms of one molecule are attracted to the negatively charged oxygen atoms of nearby water molecules

what is confirmation bias

the tendency to interpret new evidence as confirmation of one's existing beliefs or theories.

what is one characteristic of pseudoscience

it only looks for evidence that supports its claims

what is cohesion

the force by which individual molecule of the same type attract and associate

why do water molecules stick together

hydrogen bonding

what is the main property of water that allows it to be drawn up xylem vessels

cohesion

in which vessels in plants does water travel up due to cohesion

xylem

why does water have a high surface tension

the outermost molecules of water form hydrogen bonds with the water molecules below them

why is there no net force on a molecule in a body of liquid

the cohesive forces exerted by the neighbouring molecules all cancel out

why is there a net inward force on molecules on the surface of a liquid

there is no attractive force from above

give an example of an insect that exploits the surface tension of water

pond skaters

what is adhesion

the force by which individual molecules cling to surrounding materials and surfaces

materials and substances with an affinity for water are described as ...

hydrophilic

when is adhesion a significant factor in xylem transport

when air-filled xylem vessels refill with aqueous sap under positive pressures which is a rare occurrence

what are the thin, vertical channels in soil called

capillary tubes

how is water drawn up capillary tubes in soil

adhesion between water molecules and the wall of the capillary tube

what is capillary action

"Capillary action occurs when a liquid rises in a thin tube because the adhesive forces between the tube and the liquid are stronger than the cohesive forces between liquid's molecules.

what are the cell walls of plants made of

cellulose

give an example of a fibrous material

cellulose

is cellulose polar or non-polar

polar

is cellulose hydrophilic or hydrophobic

hydrophilic

what process draws water up fibrous materials

capillary action

why do most enzymes require a certain level of water in their structures

to maintain their enzyme shape and stability

what type of bond often acts as a bridge between enzyme binding sites and their substrates

hydrogen bonds

why is water liquid at room temperature

hydrogen bonds

why is CO2 soluble in water

a proportion of it undergoes a chemical reaction to form carbonic acid (H2CO3) which ionises to form hydrogen ions and hydrogencarbonate ions

why do oxygen and nitrogen have low solubility in water

they are non-polar and do not form hydrogen bonds with water

what is a consequence of the poor solubility of oxygen in water

the evolution of respiratory pigments which greatly increase the oxygen-carrying capacity of substances like blood compared to pure water

give an example of a respiratory pigment

haemoglobin

what type of asteroids are likely to have brought water and carbon compounds to earth

carbonaceous chondrites

what evidence suggests water arrived on earth through asteroids

the water found in asteroids has a similar ratio of deuterium to protium to that of the water found on earth