C4 - Chemical Changes Flashcards
how are acids made
when gases dissolve in water
what do acids produce when we add water
hydrogen
what do alkalis produce when we add water
hydroxide
what is a neutralisation reaction
a reaction between the hydrogen ions in an acid and the hydroxide ions in an alkali
what is pH
the measure of the concentration of the hydrogen atoms
on the pH scale what numbers are strong acids
0-1
on the pH scale what number are weak acids
2-5
on the pH scale what number are neutral
6-7
on the pH scale what numbers are weak alkali
8-12
on the pH scale what numbers are strong alkalis
13-14
what is acid strength
A measure of the degree of ionization of acid molecules in aqueous solution.
what do strong acids do
fully ionize
what do weak acids do
only partially ionize
what is acid concentration
A measure of the amount of acid molecules (mol) dissolved per unit volume (dm3) of water.
what can you do to increase the concentration of an acid
- removing water
- adding acid molecues
in a diagram what does a strong concentrated acid incude
- lots of acids
- lot of hydrogen
- little water
in a diagram what does a weak concentrated acid include
- little water
- little hydrogen
- lots of acid
in a diagram what does a strong dilute acid include
- lots of water
- very little acid
- few hydrogen
in a diagram what does a weak dilute acid include
- lots of water
- little acid
- few hydrogen
what experiments/practicals can compare strong and weak acids
- measuring the pH
- colour with universal indicator
- reaction with magnesium
- reaction with sodium carbonate
- conductivity
what is the order for the reactivity series in order from most reactive to least
most reactive:
- potassium
- sodium
- lithium
- calcium
- magnesium
- aluminium
- carbon
- zinc
- iron
- hydrogen
- copper
- silver
- gold
how can aluminium be extracted
electrolysis
how can zinc be extracted
smelting
what is oxidation
gain of oxygen / loss of electrons
what is reduction
loss of oxyge / gain of electrons
what is an ore
a material (rock) contaning enough metal to make it economical to extract
what is a displacement reaction
when a more reactive metal displaces a less reactive metal from its compounds
what is a salt
a compound formed when hydrogen in an acid, is completely or partially replaced by a metal
what is the salt name for hydrochloric
metal chloride
what is the salt name for sulfuric
metal sulfate
what is the salt name for nitric
metal nitrate
describe a method to make pure, dry crystals of copper sulfate
- add copper oxide to sulfuric acid in excess to use up all of the acid
- warm gently to speed up rate of reaction
- filter to remove excess copper oxide
- heat to reduce volume of solution by half
- leave to evaporate at room temp
describe how metals are extracted from low-grade ores using phytomining
- plants grow on soil containing ore
- plants take in metal compound through roots
- plants harvested and burnt
- metal is extracted from ash using electrolysis or displacement
describe how metals are extracted from low-grade ores using bioleaching
- bacteria feed on metal ions in ore to create a solution (leachate)
- metal is extracted from leachate using electrolysis or displacement
what is an inderpendant variable
a variable that stands alone and isn’t changed by the other variables you are trying to measure
what is a dependant variable
what you measure in the experiment and what is affected during the experiment
what is a control variable
an experimental condition or element that is kept the same throughout the experiment
