A1.1 -- Water

condensation reaction

(JOINS)

water formed as a product when two molecules join together.

hydrolysis reaction

(SPLITS)

water reacts with a chemical to break it into smaller molecules.

the three constituents / parts of an atom

1. proton

2. neutron

3. electron

atoms are neutral when…

they have an equal number of protons and electrons.

atoms become charged when….

there is either a deficit or surplus of electrons.

atom

the smallest particle of a chemical element that can exist

element

matter that cannot be decomposed into something simpler

*all atoms of an element have the same number of protons

molecule

atoms that are joined together by a molecular bond

compound

a molecule made up of two or more different atoms

chemical bond

an attraction between atoms/ions/molecules that enables the formation of chemical compounds

ionic bond

involves the transfer of electrons

cation = positive charge

anion = negative charge

covalent bond

involves the sharing of electrons

types of chemical bonds

1. non-polar covalent bond

2. polar covalent bond

3. ionic bond

4. hydrogen bond

non-polar covalent bond

electrons are shared equally

polar covalent bond

electrons are shared unequally

ionic bond (within a molecule)

attraction between a positively charged ion (cation) and a negatively charged ion (anion)

hydrogen bond (between different molecules)

attraction between 𝛿+ and 𝛿− regions of two different polar molecules

*intermolecular force, not an actual bond

structure of a water molecule

dissolving

when a molecule is separated by another because it is attracted to something

water molecules are polar — where are the electrons polled towards?

the oxygen atom

why do hydrogen bonds form between water molecules?

because the 𝛿+ hydrogen atoms of one water molecule are attracted to the 𝛿− oxygen atom of another water molecule.

what is the maximum number of H-bonds a water molecule can form with other water molecules?

four

cohesion

the ability of water molecules to form hydrogen bonds with each other, causing them to stick together.

cohesion-tension model

*most widely accepted model for movement of water in vascular plants

1. transpiration (evaporation) occurs because somata are open. as transpiration occurs, it creates negative pressure called tension/suction.

2. tension created by transpiration ‘pulls’ water in the plant xylem, drawing it upwards.

3. cohesion pulls up water molecules in a chain as the top-most water is pulled up and out of the somata.

surface tension

a property of the surface of a liquid that allows it to resist an external force, due to the cohesive nature of its molecules.

occurs because the outermost layer of molecules are left with fewer molecules to cling to, instead compensating by establishing stronger bonds with neighbours that they do have contact with, creating an inward force.

adhesion

the attraction of water to other polar or charged molecules.

cellulose

a polymer made of glucose units, present in plant cell walls.

*water forms H-bonds with cellulose because of -OH groups in glucose that water sticks too. this allows structures with lots of cellulose to absorb water.

capillary action

the movement of water through a narrow space, often in opposition to external forces (gravity).

• helps bring water from the roots

• helps soil retain water

capillarity

the rate at which water is pulled upward from the water table into pore spaces (spaces between soil particles) by capillary action.

*the height to which the water rises depends on the type of soil

**different soils have different capillarity rates

solvent

the liquid in which a solute dissolves

solute

the substance that dissolves in a solvent

solution

a mixture of one or more solutes dissolved in a solvent

solvation

the interaction of a solvent with a dissolved solute

*water forms H-bonds with a solute, forming a hydration shell around it.

hydrophilic molecules

molecules that attract water (generally soluble)

*polar, with a charge

hydrophobic molecules

molecules that cannot attract water (insoluble)

*non-polar, without a charge

**hydrophobic molecules attract each other, and will clump together when exposed to water

cytosol

the liquid part of the cytoplasm (a structure common to all cells)

catabolic reactions

break down larger molecules into smaller molecules

anabolic reactions

build larger molecules using smaller molecules

why is water necessary for cellular metabolism?

it dissolves reactants and enzymes, so that they can come together for reactions.

how can water be a medium of transport?

dissolved solutes can be transported in solution around the body of an organism.

buoyancy

an upward force applied to an object that is immersed in a fluid

how is buoyancy calculated?

if the buoyant force of the fluid is greater than the objects weight, the object will float.

*buoyancy of a fluid is dependent on its density

density of object > density of fluid = object will float

density of object < density of fluid = object will sink

viscosity

a measure of a fluid’s tendency to flow

what causes / determines viscosity?

the amount of friction the molecules of a liquid experience as they flow over each other.

thermal conductivity

a measure of a material’s ability to move heat across a temperature gradient

what determines thermal conductivity

how easily energy transfers through the material

low conductivity = heat moves slowly through the material (good for insulation)

high conductivity = heat moves rapidly through the material (good for absorbing/transferring heat)

specific heat capacity

the quantity of heat needed to raise the temperature of a chemical, per unit mass.

*water has the highest heat capacity of any liquid.

how has the ringed seal adapted to its environment?

• buoyancy in water allows the seal to stay afloat without expending much energy

• the seal has adaptations for streamlining as it swims due to the viscosity of water

• insulated with blubber to retain body temp due to water having a higher thermal conductivity than air

• high specific heat of water provides a stable habitat for the seal to live

scientific name of the ringed seal

pusa hispida

how has the black throated loon adapted to its environment?

• buoyancy in water allows the bird to stay afloat without expending much energy

  *must expend energy when flying through air though

• air is not viscous, which allows the loon to move through it easily when flying

• the loon does not lose much body heat when in the air, due to the air having a low thermal conductivity

  *the low specific heat of air means that its temperature also changes as rapidly though

scientific name for black throated loon

gavia arctica

extraplanetary object

an object from outside earth’s orbit

the most likely source of water on earth

carbonaceous chrondite asteroids

what are the two reasons that earths surface is able to retain water

1. being in the goldilocks zone means that the surface is neither too hot nor too cold for the existence of liquid water

2. gravity

goldilocks zone

the orbital distance from a star that will result in liquid water

(ie the surface temperature is neither too hot nor too cold)

what evidence suggests that water on earth originated from asteroids?

the deuterium to hydrogen ratio in carbonaceous chrondite asteroids is similar to that of the water in earth’s oceans, suggesting a common origin

what are the three circumstances that astrobiologists look for when searching for extraterrestrial life?

1. luck (less important) - all the right chemicals existing in the same place at the same time

2. time - earth’s complex life took billions of years to evolve

3. location - celestial bodies in the goldilocks zone

what are the chemicals that astrobiologists look for when searching for extraterrestrial life?

1. water — the presence of water is considered the precedent to the search for extraterrestrial life

2. carbon

3. nitrogen

4. phosphorus

5. sulphur