chemistry stuff i don't remember

lithium reaction with water

effervescence

moves around on surface

eventually disappears

sodium reaction with water

lot of effervescence

melts into a ball

moves around on surface

eventually disappears

potassium reaction with water

lots and lots of effervescence

burns with a lilac flame

moves around on surface

eventually disappears

iodine appearance at room temperature

shiny grey-black solid

iodine water appearance at room temperature

yellow-/red-brown liquid

percentages by volume of 4 most abundant gases

78% nitrogen

21% oxygen

1% argon

0.05% carbon dioxide

describe the combustion of magnesium in air

exothermic - releases heat

burns with a bright white light

produces white powder - magnesium oxide

describe the combustion of hydrogen in air

burns to form water vapour

describe the combustion of sulfur in air

burns with a blue flame

produces a colorless, pungent gas - sulfur dioxide - which is toxic

and dissolves into the air to form sulfuric acid (acid rain)

describe thermal decomposition of copper(II) carbonate

endothermic reaction - when heated

breaks down to form carbon dioxide and copper oxide

goes from green to black

reactivity series acronym

Please Stop Literally Calling Me A Careless Zebra, Instead Try Learning How Copper Saves Gold

reactivity series

Potassium Sodium Lithium Calcium Magnesium Aluminum Carbon Zinc Iron Tin Lead Hydrogen Copper Silver Gold

conditions needed for iron to rust

oxygen & moisture

barrier method to prevent rusting

cover iron with physical layer e.g. paint to prevent contact with air

galvanizing to prevent rusting

coating iron in more reactive metal (usually zinc) which reacts instead

sacrificial protection to prevent rusting

placing a more reactive metal (usually zinc) near to the iron and it reacts preferentially with oxygen

what is redox

where both reduction (gain of electrons) and oxidation (loss of electrons) happen

what is an oxidizing agent

something that causes another substance to be oxidized (lose electrons/gain oxygen) and is itself reduced

what is a reduction agent

something that causes another substance to be reduced (gain electrons/lose oxygen) and is itself oxidized

litmus colour change

red in acid, blue in alkali

phenolphthalein colour change

colourless in acid, pink in alkali

methyl orange colour change

red in acid, yellow in alkali

acid proton transfer

acid is a proton (H+) donor

base proton transfer

base is a proton (H+) acceptor

how to test for ammonium ions

add sodium hydroxide solution

test evolved gas with damp red litmus paper (turns blue)

how to test for copper, iron(ii) and iron(iii) ions

add sodium hydroxide solution

copper → blue precipitate

iron(ii) → green precipitate

iron(iii) → red brown precipitate

how to test for chloride, bromide, and iodide ions

add nitric acid and silver nitrate

chloride → white precipitate

bromide → cream precipitate

iodide → yellow precipitate

how to test for sulfate ions

add hydrochloric acid and barium chloride

white precipitate forms

how to test for carbonate ions

add hydrochloric acid

test evolved gas with limewater

should go cloudy

how to find joules released by a reaction

Q = m x c x /\T

heat energy change = mass of water x 4.2 x change in temperature

how to find molar enthalpy change from Q heat energy change

/\H = Q / mol

= heat energy change IN KJ / moles of thing burned

sign for exothermic reaction

NEGATIVE

sign for endothermic reaction

POSITIVE

why does increasing pressure increase rate

increased pressure particles are closer together

so collide more

so more frequent successful collisions

catalyst definition

a substance that increases the rate of reaction by providing an alternate pathway for a reaction with a lower activation energy, which is chemically unchanged at the end of the reaction

why can nitrous oxides form in car engines?

the temperature is high enough that the nitrogen (which is usually very stable) and oxygen in the air react together

describe catalytic cracking [4]

long-chain alkanes

converted into alkenes and short-chain alkanes

by heating to 600 degrees Celsius

with silica or alumina as a catalyst

how can burning hydrocarbons lead to acid rain [5]

hydrocarbon fuels often contain sulfur impurities

when burned these become sulfur dioxide

which mixes with water & oxygen in clouds

to become sulfuric acid

which falls as acid rain

describe the reaction of alkanes with halogens [4]

only happens in the presence of UV light

substitution reaction

halogen atom(s) replaces hydrogen atom(s)

e.g. bromine + ethane to form bromoethane and hydrogen bromide

describe the reaction of alkenes with halogens [4]

addition reaction

double bond in alkene splits

e.g. bromine + ethene to form dibromoethane

if w/ bromine, goes from orange-brown to colourless

how to distinguish between alkane and alkene

add bromine water

alkane = no change (stays orange-brown)

alkene = turns colourless

how is an addition polymer formed

by joining up many small monomer

2 problems with addition polymers

inert & unable to biodegrade

produce toxic gases when burned