CHEMISTRY AQA PAPER1 gcse

relative charge of a neutron

0

Relative mass of a neutron

1

whats an isotope

Different forms of the same element; same number of protons but different number of electrons

Where is (most of the) the mass of an atom

Nucleus

What is a compound

A substance formed from two or more different elements in fixed proportions, held together by chemical bonds

What is a mixture

two or more elements or compounds that are combined but not chemically bonded together

Explain how paper chromatography could separate a mixture containing three separate dyes

put a dot of each dye mixture on the pencil line and place filter paper in solvent.

The solvent should be below the pencil line

Each different dye will move up the paper at a different rate, separating them

When do u use filtration

On a mixture of an insoluble solid and aliquid

When to use crystallisation

To separate a soluble solid from a solution

How does filtration work

Passing the mixture through a filter

Insoluble particles caught by the filter

Why crystallisation insead of evaporation

If the salt will decompose when heated.

Or want big crystals of salt

How to do crystallisation (makins salts practical)

Heat the acid using bunsen burner until almost boiling

Add small amounts of copper oxide powder and stir

Continuously add copper until it is in excess

Transfer remaining solution into crystallising dish and leave in cool place for atleast 24h

Remove the crystals and gently pat dry to remove excess liquid

How to separate sand and salt mixture

Filtration then crystallisation

when to use fractional distilation

Mixtures of liquids including those of similar boiling points

When to use simple distillation

To separate a liquid from a solution

Diff boiling points

How to fractional distillation

Flask below a fractionating column Connected to a condenser and has a thermometer at the top

Pour mixture into flask and heat to bliling point of liquid you want to separate out

Desired liquid should evaporate and travel up fractionating column and into the condenser

In condenser it turns back into a liquid where it can be collected.

Plum pudding model

Atoms as balls of positive charge with electrons stuck to them

Bohr arrangement

Electrons orbit the nucleus in shells that are a fixed fistance from the nucleus

How were alpha particles used to disprove plum pudding model

Fired at a thin sheet of gold. Most particles went straght through the sheet but some were deflected

This meant the positive charge couldnt be spread out evenly between the atoms, as the plum pudding model described

electronic structure

max 2 first shell

max 8 in other shells

Elements in the same group (column)

Have the same number of electrons in their outer shell

What is a metal

Elements which can form positive ions

Why can elements toward the bottom of the periodic table lose electrons easily

More shells of electrons than elements at the top, so outer electrons are further from the nucleus - weaker attraction

Where r metals on the periodic table

Toward left and bottom

Where transition metals on Ptable

Centre

Metals properties

Strong, malleable, good conductors of elec, high melting and boiling points

Transition metals compared to group 1 metals

More dense than group 1

Higher melting points

iron in the harber process

A catalyst to speed up the reaction

(Transition metals make good catalysts)

Alkali metals (group 1 metals)

reactivity increases as you go down the column. Becuase the outer electron is further away from nucleus so less attracted and more easily lost.

Potassium with water

Vigorously

Hydrogen produced so bubbling and fizzing

Flame

Alkali metals properties

Soft, low density

Group 7 (halogen ions) charge

Need to gain one electron to complete outer shell, form 1- ions

What happens as you go down group 7 in Ptable

Boiling points and melting points of the halogens increase

Trend of reactivity decreases becuase its harder to gain an electron as there is thess attraction as the outer shell becomes further from the nucleus

Halogen molecules

All halogens exist as molecules such as f2

Group 0 elements

Noble gases

Nobles gasses monatomic gases

Are single gases not bonded to each other

Noble gases inert

because they have full outer shells so dont need to lose or gain any electrons to become stable

Metal + oxygen

Metal oxide

Who discovered neutrons

Chadwick

Mass number

Protons + neutrons

Atomic number

Num of protons and num of electrons

Metal + water

Metal hydroxide

Solid

Fixed state cant flow but can vibrate

Cant be compresed

Liquid

Can move

Not in a fixed position

Can flow

Cant be compressed

Gas

Mot fixed

Can flow

Can be compressed

Liquid + liquid → solid OBSERVATIONS

Cloudy

Liquid + solid → gas OBSERVATIONS

Bubbles

Loss of mass

Fizzing

Liquid + liquid → gas OBSERVATIONS

Bubbles

Loss of mass

Fizzing

ionic bonding

The transfer of electrons from a metal to a non metal

Group 1 ionic bonding

Forms 1+ ion

Group 2 ionic bonding

Forms 2+ ion

Group 6 ionic bonding

Forms 2- ion

Group 7 ionic bonding

Forms 1- ion

Ionic bond

The electrostatic Attraction between oppositely charged ions

Ionic bonding diagram

Covalent bonding

The sharing of electrons between two non metals

Covalent bonding diagram

melting point of ionic compounds

High melting point

Because it takes alot of energy to overcome the strong electrostatic attraction between the oppositiely charged ions

Electrical conductivity of ionic compounds

Good electrical conductivity when liquid or aqueous NOT when solid

Because when liquid or aqueous there are charged particles that can move and carry charge throughout the structure

Dissolve? Ionic compounds

sometimes/often dissolve

Depends if the attraction between the ions and water is greater than the attraction between the ions

Ionic compounds strength?

Strong but brittle

Electroststic repulsion shatters the lattice due to strong bonds (if one layer is moved)

Giant ionic lattice

Positively and negatively charged ions attract each other in all directions to form this

(One ion is ionically bonded to many others)

2 types of Covalent structures

Simple molecular

Giant lattice

Covalent simple molecular boiling point

Relatively low melting points

Doesnt take much energy to overcome the weak intermolecular forces

Covalent simple molecular electrical conductivity

Does not conduct electricity

There are no charged particles to move or carry charge throughout the structure

Covalent simple molecular dissolve?

Does not dissolve in water but does in organic solvents

Polymers

A substance made up of many monomers joined together

Diamond structure

Giant covalent lattice

Each carbon atom forms 4 covalent bonds with other carbon atoms

Diamond electrical conductivity

Poor/none because there are no charged particles to move or carry charge throughout the structure

Diamond melting point

High melting/boiling point

it takes alot of energy to overcome the strong covalent bonds

Diamond soft/hard

very hard

The atoms are held in place by strong covalent bonds

Why graphite in lead of pencils

The layers are scraped off onto the paper due to the weak attraction between the carbon atoms with no covalent bonds between the layers

Graphite structure

giant covalent lattice

Each carbon atom forms 3 covalent bonds w/ other carbon atoms, forming layers of hexagonal rings (with no covalent bonds between layers)

One electron from each carbon atom is delocalised

Graphite electrical conductivity

Can conduct electricity

Because the delocalised electrons can move and carry charge throughout the structure

Graphene structure

A single layer of graphite →

One layer of hexagonal rings of C atoms covered in delocalised electrons

Graphene uses

Electronics - becuase it conducts electricity

Composites - because it has a high strength to weight ratio

Fullerenes structure

Hollow cage of C atoms based on graphene

Hexagonal rings of C atoms although may also contain 5C or 7C rings

Very long and thin → high length to diameter ratio

Diameter = 1 × 10^-9m

Buckminster fullerenes (bucky balls) structure

Carbon nanotubes

C60 (60 carbon atoms all together)

Simple molecular

Bucky balls uses

Lubricant or reinforcement

Metalic bonding structures

Giant metallic lattice

Ionic bonding structures

Giant ionic lattice

Metallic bonding structures

Giant metallic lattice

Giant metallic latice structure

Metal ions close packed

Delocalised electrons in the structure

metals melting point

High melting point

It takes alot of energy to overcome the strong electrostatic attraction between the positively charged ions and the delocalised electrons

Metals malleable?

Yes

The layers of ions can slide over each other as they are in a sea of delocalised electrons and are not in a fixed position - soft

Metals electrical conductivity?

Good electrical conductivity

Because the delocalised electrons can move and carry charge throughout the structure

Metals therman conductivity?

Good thermal conductivity

The delocalised electrons can move and transfer heat energy through the structure

Alloys

Mixtures of a metal with atleast ine other element (usually another metal)

Alloy strong?

Stronger and harder than a pure metal becuase the layers cant slide over eachother

Alloys electrical conductors

Less efficient electrica conductors than pure metals

Have irregularities in the lattice → scattered delocalised electrons, so less easy for electricity to carry through the structure

Nanoparticle measurement

1nm = 1 × 10^-9m

nanoparticle SA

high SA to volume ratio → smaller quantities needed to be effective.

Nanoparticle uses

Cosmetics, medicine, electronics, catalysts

Nanoparticle issues

Small enough to go through pores and into blood stream which can cause problems (cosmetics)

Percentage yield

(Actual yield / theoretical yield) x 100

Why can % yield sometimes be under 100

Some products lost on transfer

Could be a redox reaction

Unexpected side reactions

moles

Mass / mr

Atom economy

(Mr of desired products / total mr of reactants) x100

moles to volume

x 24 (24dm³)

volume to moles

divide by 24 (24 dm³)