1.7 water

nitrate ions function

to make DNA and amino acids

calcium ions

to form calcium pectate for middle lamellae

magnesium ions

chlorophyll

phosphate ions

ATP and ADP

water molecules are polar

this is because oxygen is more electronegative (likes e- more) this makes them pull more electrons closer to it making the oxygen side slightly negative and hydrogen side slightly positive

polar molecule

molecules are always neutral

but in a polar molecule there is an uneven distribution of electrons making an area more negative and some areas more positive

examples of charged ions, polar molecules and non polar molecule

charged ions: K+, Na+

polar molecules: H2O, glucose

non polar molecules: O2, CO2

formation of hydrogen bonds

when the slightly positive hydrogen atom is attracted to the slightly positive oxygen atom of another water molecule

H bonds in water

there is a large amount of hydrogen bonds in water which is stronger than intermolecular forces, and the hydrogen bonds gives special properties to water

5 properties of water

• high specific heat capacity

• polar solvent

• surface tension

• incompressibility

• maximum density at 4°C

high specific heat capacity

(heat energy needed to raise the temperature of 1g of the substance by 1°C)

• more energy needed to change temp (stable temperature) = 4.18J → bc large amount of hydrogen bonds and takes lots of energy to break

animals: thermally stable environment for aquatic animals

humans: body consists of 70% water → maintains body temperature

water is a good solvent

(only for charged and polar molecules)

• when a molecule is dissolved the ions are seperated so they dont disappear they are just so small we can no longer see them

• the water molecules seperates the ions (negative H2O side to the positive ion and positive H2O side to the negative ion)

role of water as a medium of transport

human:

• blood: mainly plasma (good solvent for charged/polar molecules)

(if molecule is not polar eg. oxygen, they will be carried by haemoglobin)

cohesion

forming Hydrogen bonds between water molecules (hydrogen bonds form cohesive forces and allows water to never break so there will be a continuous column of H2O)

• allows water to travel up xylem and blood to more continuously in body

water surface as a habitat

• because there is a lot of hydrogen bonds, it gives a cohesive force, giving water a high surface tension

• supports small insects that dont have enough energy to break the hydrogen bonds in water

adhesion

hydrogen bond between water molecule and other polar molecules (gives capillary action)

water’s maximum density is at 4°C

• because ice forms at 0°C and it floats so water at four degrees sink to the bottom making the density high

• as liquid is not frozen under the ice (organisms stay alive)

why are electrons more attracted to oxygen

because oxygen has a bigger nucleus which means it has a greater affinity