IGCSE Chemistry Revision FULL (copy)

solids

1. particles vibrate at a fixed position
2. little kinetic energy
3. strong forces between particles

liquids

1. particles are more spaced apart
2. intermediate forces between particles
3. higher vibration
4. do not have fixed positions

gases

1. particles are much further apart
2. large amounts of kinetic energy
3. not held in fixed positions
4. very weak forces between particles

melting

solid to liquid

boiling

liquid to gas

evapouration

surface liquid to gas

freezing

liquid to solid

condensation

gas to liquid

gas compression

the pressure within the container will increase

brownian motion

random particle movement in suspension

diffusion

the net movement of particles from an area of high concentration to an area of low concentration down a concentration gradient as a result of random movement
- no energy is required for this process

ammonia and hydrochloric acid diffusion

1. place substances in opposite ends of the glass tube
2. a white ring of ammonium chloride will form where the ammonia and hydrochloric acid meet
3. the location of the white ring determines the rate of diffusion; middle of the tube means the substances diffused equally
4. usually forms closer to the hydrochloric acid because ammonia has a smaller atomic mass and diffuses quicker

apparatus

gauze, evaporating basin, tripod, beaker, conical flask, filter funnel, filer paper, measuring cylinders, scales, thermometer, stopwatch, pipettes (titration), burette

solute

solid which dissolves in a solvent

solvent

liquid in which the solute dissolves

solution

mixture of solute and solvent

saturated solution

cannot dissolve any more solute into the solvent (at its maximum capacity

filtration

insoluble solute from a solvent (e.g. sand and water)

evaporation

soluble solvent from a solvent (e.g. salt water)

simple distilation

separate liquids at different boiling points

fractional disillation

separates many liquids at different boiling points

chromotography

separation of inks and dyes; ink that travels furthest is the most soluble

Rf formula

distance travelled by component / distance travelled by solvent

importance of purity

- drug safety
- prevention of contamination
- needed for food

blast furnace equations

iron oxide + coke --> iron + carbon dioxide
Fe2O3 + 3CO --> 2Fe + 3CO2

limestone is added; removes acidic impurities
SiO2 + CaO --> CaSio3 (slag)

electrolysis

uses electricity to purify metals; only for metals more reactive than carbon. the metal is reduced: loses O2, gains e-

atoms

smallest particle of an element that can exist

element

only has one type of atom and cannot be separated by any chemical means

compounds

more than two elements that are chemically combined (cannot be separated back into their constituent elements)

mixture

two elements not chemically combined

pure substance

contains only one type of material; they have a fixed boiling point

molecule

two or more atoms bonded together

nucleus

contains protons and neutrons

mass of protons

1

mass of neutrons

1

mass of electrons

1/2000

charge of neutrons

0

charge of protons

+1

charge of electrons

-1

atomic number

number of protons found in the nucleus of an atom

mass number

total number of protons and neutrons

nucleon number

total number of protons and neutrons (i.e. the mass number)

isotopes

atoms of the same element with different number of protons but the same number of neutrons

group numbers

corresponds to the number of electrons in outer shell

period number

corresponds to the number of shells

properties of the elements in the same group

they have the same properties due to the number of electrons in their outer shell

the noble gases

they are unreactive because they have a full number of electrons in their outer shells; will not bond

metals

1. high melting + boiling point
2. shiny and sonorous
3. good conductors of heat and electricity
4. malleable and ductile

metal bonding

when they bond they tend to lose electrons to become positive ions. forms basic oxides and take part in ionic bonding

non-metals

1. low boiling + melting points
2. dull and brittle

non-metal bonding

the tend to gain electrons to become negative ions. forms acidic oxides and take part in covalent + ionic bonding

ion

charged particle formed from gaining or losing electron

ionic bonding

metal and non-metal elements bonding

covalent bonding

non-metal and non-metal elements bonding

giant covalent structures

diamonds and graphite

allotrope

different forms of the same element

ionic bonds

the electrostatic attraction between two oppositely charged ions (metals +ve and non-metals -ve)

electricity and giant ionic structures

they do not conduct electrons when solid because ions are not free to move; however they do conduct electricity when molten because ions are free to move

metallic bonding

electrostatic attraction between positive ions and the sea of delocalised electrons

how much (any) gas is occupied per 1 mol

24dm^3

diamond

1. high melting point
- tetrahedral structure
- C atom is bonded to 4 others
- many strong covalent bonds
- requires a lot of energy to break
2. does not conduct electricity because electrons are not free to move

graphite

1. high melting point:
- C atom is bonded to 3 others; however this makes graphite's melting point slightly lower than diamonds
- many strong covalent bonds
- requires a lot of energy to break
2. conducts electricity because the charge is carried on the delocalised electron (C atom bonded to 3 others)

graphite as a lubricant

the structure of graphite has many layers of C atoms which breaks easily due to the weak intermolecular forces between them; the layers slide off each other when broken. this also requires little energy to break.

Ammonium

NH4+

Silver

Ag+

Copper

Cu2+

Lead

Pb2+

Zinc

Zn2+

positive anode in aqueous solution

attracted to least reactive negative halogen (e.g. Cl-)

negative cathode

attracted to least reactive positive ion (e.g. H+)

electrolysis in lead (II) bromide

compounds present: Pb2+, Br-

1. anode (+)
attracts: Br-
observations: lead drips in molten state

2. at the cathode (-)
attracts: Pb2+
observations: bromine gas is produced

electrolysis in aqueous sodium chloride

ions present: Na+, Cl-, H+. OH-

1. anode (+)
attracts: Cl- *least reactive negative halogen ion*

2. cathode (-)
attracts: H+ *least reactive positive ion*

electrolysis in aqueous sulphuric acid

ions present: SO4^2-, OH-, H+

1. anode (+)
attracts: OH- *least reactive negative halogen ion*
observations: colourless gas is given off; tested by relighting a glowing splint over oxygen

2. cathode (-)
attracts: H+ *least reactive positive ion*
observations: colourless gas is given off; tested by inserting lighted splint into test-tube containing hydrogen, a squeaky 'pop' sound is produced

conclusion for the electrolysis in aqueous sulphuric acid

anode: hydroxide ions move to the positive anode. every four hydroxide ions discharged produces an oxygen molecule

cathode: hydrogen ions move to the negative cathode and receive electrons to form hydrogen atoms. two hydrogen atoms combine to make a hydrogen molecule

electroplating

1. the metal coating of the object is the anode (+)
2. the object that is being coated is the cathode (-)

electrolyte

the solution of a soluble compound of the metal

uses of electroplating

- jewellery; usually copper coated with silver; silver is very expensive and rare
- steel bumpers on cars; chromium; very hard and shiny, however it's very expensive
- tin cans; steel coated with tin; tin is corrosive resistant

oxidation

the loss of electrons

reduction

the gain of electrons

redox

when the loss AND gain of electrons occur

reducing agent

causes other substances to be reduced *however, reducing agents themselves are oxidised*

oxidising agent

causes other substances to be oxidised *however, oxidising agents themselves are reduced*

rate of reaction: ^ in temp.

1. higher rate of reaction
2. increase in kinetic energy in particles
> leads to an increased frequency in particle collision
> this means an increase in successful particle collision

rate of reaction: ^conc.

1. more particles are present
2. more frequent particle collision
3. more successful particle collison

rate of reaction: ^s.a.

1. more area means more particles to collide
2. more successful particle collision

dangers of increased rates of reaction

1. flour mills
- flour has an extremely tiny particles; they have an incredibly large surface area
- these particles are flammable
- flame can cause explosion
2. coal mines
- CH4 (methane) is present in the coal mines
- CH4 (methane) is EXTREMELY flammable
- a single spark will cause an enormous explosion

soluble

1. nitrates
2. potassium, sodium, ammonium compounds
3. all sulfates except:
- lead (II) sulfate
- barium sulfate
- calcium sulfate
4. all chloride except:
- lead (II) chloride
- silver chloride

insoluble

1. all carbonates except:
- potassium carbonate
- ammonium carbonate
- sodium carbonate
2. all hydroxides except:
- potassium carbonate
- sodium carbonate
- ammonium carbonate

soluble salts

- use appropriate: metals, metal oxides, metal hydroxides, metal carbonates
- acid

forming soluble salts

crystallisation; do not contain K, Na or NH3

crystallisation

1. reacts (metal... and acid)
2. filter; gets rid of any undissolved solids
3. evap.; gets rid of excess water
4. cool; collect crystals formed
5. dry; leave crystals in warm place/on filter paper

making insoluble salts

1. react (two soluble salts)
2. filter; gets rids of insoluble solids
3. wash; gets rids of insoluble solids
4. dry; leave ppt. in warm place/on filter paper

aqueous cations

ammonium, copper, calcium, iron (ii), iron (iii), zinc

aqueous anion

carbonate, chlorine, bromine, nitrate, sulfate

test for ammonium

sodium hydroxide:
- ammonia produced on warming
ammonia:
- none

test for copper

sodium hydroxide:
- blue ppt.
- insoluble in excess
ammonia
- blue ppt.
- soluble in excess: dark blue sol.

calcium

sodium hydroxide:
- white ppt.
- insoluble in excess
ammonia:
- no/very slight white ppt.

iron (ii)

sodium hydroxide:
- green ppt.
- insoluble in excess
ammonia:
- green ppt.
- insoluble in excess

iron (iii)

sodium hydroxide:
- red-brown ppt.
- insoluble in excess
ammonia:
- red-brown ppt.
- insoluble in excess

zinc

sodium hydroxide:
- white ppt.
- soluble in excess - colourless solution
ammonia:
- white ppt.
- soluble in excess - colourless solution