C1- C7 paper 1 GCSE

paper 1 AQA combined science, chemistry

elements are made of

one **type** of atom, so they can be made of multiple atoms

compounds

contains two or more elements or type of atom

no energy can be

created or destroyed

a mixture

two or more substances that are not chemically bonded

mixtures can be separated using physical methods of

filtration, crystallisation and simple distillation

fractional distillation

it uses a fractionating column and heats it to the lower boiling point and collects that evaporated substance

paper chromatography

a mixture of liquids are separated depending on the solubility of the substance

key ideas about the atom came from

Bohr, Dalton, Thompson, Rutherford

what did Dalton suggest

he said that atoms where a tiny hard sphere that can’t be split

what did Thompson suggest

he discovered electrons and proposed they were embedding in a ball of positive

gold foil experiment

they fired densely positive particles (or alpha particles) at very thin gold foil

* most went through showing it is mostly empty space
* few were repelled showing it has a tiny centre that is positively charged, not all positive like the previous model suggested

what did Bohr suggest

he took the nuclear model (where the protons are at the centre and electrons orbit it) he said the electrons are orbiting in shells

what did Chadwick discover

the nucleus contains uncharged neutrons in 1932

isotopes

have the same atomic number but a different mass number, they have gained/ lost

ions

a charged atom, it has gained/ lost an electron

what is the lowest/ highest energy shells

the first shell has the lowest energy and can only hold 2 electrons while all the next shells increase in energy and can hold 8 electrons

what determines the group of an atom

the number of atoms on the outermost shell

what determines the period of an atom

the number of shells it has

original periodic table was organised by

atomic weight

why is it called a **periodic** table

there are regular repeating patterns to the elements

Mendeleev’s periodic table

he put them in order of atomic weight but left spaces for undiscovered elements

the outer shell

determines the chemical properties of the atom

metals vs non-metals

metals normally lose electrons non metals gain them

why are non-metals unreactive

the have a full outer shell so they are stable

group 1

alkali metals

group 1 mp/ bp

the melting and boiling point decrease going down the group

group 1 reacts with water

to produce hydrogen and an alkali solution containing metal hydroxide

ions/ bonding of group 1

they form a 1+ ion and forms an ionic compound. Their compounds tend to be white/ colourless crystals that when combined with water produce a colourless solution

the reactivity of group 1

increases as you go down the group

group 7

halogens

group 7 with metal

form a single negative charge in their ionic bond with metal

group 7 with non-metal

forms a covalent bond by sharing electrons with a non-metal

more/ less reactive halogens

a more reactive halogen can displace a less reactive one in a solution

reactivity in group 7

halogens decrease as you go down the group

explaining reactivity going up/down a group

* if an atom wants to gain an electron it will become less reactive as you go down the group, as the electrostatic attraction to the nucleus gets weaker the further it is
* if the atom wants to lose an electron it will do the opposite

factors affecting electrostatic attraction

* distance from the nucleus to the outermost electron
* number of occupied groups due to shielding effect
* the nuclear charge (size of the positive charge)

properties of transition metals

* very high m/bp
* high density
* strong and hard
* less reactive
* don’t vigorously react with oxygen or water

transition metals can

form ions of different charges that are often coloured

transition metals and their compounds are often used as

catalysts in the industrial sector

in melting and boiling

energy is transferred from the surroundings into the substance

limitations of the simple particle model

* particles are not solid spheres with no force between them
* particles can be:
* atoms, molecules and ions
* vary in size
* contain many atoms
* are not solid/ spherical

elements into compounds

by gaining/ losing electrons or sharing pairs of electrons

covalent bonding

non-metals sharing pairs of electrons

ionic bonding

non-metals and metals gain or lose electrons so one becomes a positive ion and the other becomes a negative ion

ionic compounds

are held together with strong forces of attraction can also be called ionic bonding

giant ionic structures

it takes a lot of energy to break several ionic bonds acting in all directions. Which means they have a high melting point and are a solid at room temperature.

properties of giant ionic structures

* high melting and boiling point
* can conduct electricity when molten or in solution (ions are mobile and can carry charge)
* strong electrostatic forces in all directions

properties of simple molecules

* low melting and boiling point
* weak intermolecular forces makes the m and bp low
* no overall charge so they can’t conduct electricity

properties of giant covalent

* high melting and boiling point
* need a lot of energy to break the bonds

diamond

* giant covalent structure, each atom forms with 4 other carbon atoms
* the 4 covalent bonds make it very hard, resulting in a very high melting and boiling point
* don’t conduct electricity

graphite

* each carbon atom bonds with 3 other atoms, so there is delocalised electron which allows it to conduct electricity
* it is formed in layers but there is no covalent bonds between them meaning they can easily slip, making graphite soft

graphene

a single layer of graphite that is a single atom thick and conducts electricity very well

atom arrangement in metals

closely packed together and in regular layers

metallic bonding

positively charged metal ions held together by electrons on the outermost shell

bending metals

metals can be bent and shaped because they are formed in regular layers

alloys

alloys are a mix of pure iron with some other one, it makes it stronger than a pure metal cos it interrupts the regular layers

conducting in metals

metals have a delocalised electron which makes it very easy to conduct electricity and heat

relative atomic mass

the relative mass of each atom compared to carbon-12

relative atomic mass (A^r)

mean relative mass of an atom compared to a standard carbon atom (just the top number)

relative formula mass (M^r)

adding the A^r of each atom to find the mass of the whole formula (CO2)

mole

the M^r or the A^r presented in grams

Avogadro constant

a mole of any substance will have the same number or moles, atoms or ions (6.02x10^23)

how to calculate number of moles

mass(g)/Ar or mass(g)/Mr

percentage yield

(mass of product produces/ maximum product produced) x 100

yield

how much product is made

factors affecting yield

* product left in apparatus
* reversible reactions not being completed
* unexpected reactions
* loss due to separating product from reactant

concentration

how much solute is dissolved in the solution, measured in grams per decimetre cubed

equation for concentration

mass of solute / volume of solution (if it is cm cubed do x1000)

reactivity series

metals placed in order of how reactive they are with water and dilute acid

test for hydrogen gas

squeaky pop- use a lit splint and put down the test tube and it’ll make a pop sound

displacement reaction

a more reactive metal can displace a less reactive one in an aqueous solution

why are hydrogen and carbon in the reactivity series

even though they are not metals, they are uses to show the displacement reaction

oxidation

losing electrons

reduction

gaining electrons

ore

contains enough metal to e economic to extract, might need to be concentrated before it can be extracted and purified

native state

unreactive metals like gold are not found in ore

purpose of reactivity series

helps you decide which extraction is the best for the metal

metals less reactive than carbon

carbon can reduce the metal oxide to produce the metal

metals more reactive than carbon

need to be extracted using electrolysis

salt

formed when the hydrogen in an acid is replaced by a metal

to create a salt it needs

to be above hydrogen in the reactivity series so it can displace it

what is produced when reacting metal and acid

hydrogen gas and the salt, the salt can be obtained by evaporating out the liquid

what type of of reaction is salt from metal

a reduction

neutralisation

a reaction between an acid and a base

what is produced when an acid and base react

water and a salt

how to get salt from an acid-base reaction

crystallise it out of the solution by evaporating off most of the water and drying with filter paper

why do you need an indicator when making salt

when soluble salt is made it can look like there is no change so you need a indicator or a pH meter to show change in pH

carbonate and acid produces

salt, water and carbon dioxide

acid + water produce

H+ (aq) ions

bases

substances that will neutralise an acid

alkali + water produce

OH- (aq) ions cos they are soluble hydroxide

if the pH decreases by 1 unit

the concentration of hydrogen increases by a factor of 10

electrolysis

breaks down molten or in solution ionic compounds into elements using electricity

cathode

the negative electrode that attracts positive ions

anode

the positive electrode that attracts negative ions

at the anode

the negative ion loses its extra electron and becomes an element (oxidation)

at the cathode

the positive ion gains its extra electron and becomes an element (reduction)

cathode (H+ or metal)

metal if it is less reactive than hydrogen otherwise hydrogen

anode (OH- or non-metal)

Oxygen is produced unless the non-metal is a halogen (group 7)

bauxite

aluminium oxide ore