Chapter 5 - Chemical Changes Flashcards
metal + oxygen –>
metal oxide
Metal + water —>
metal hydroxide + hydrogen
Metal + acid —>
salt + hydrogen
How does potassium, sodium and lithium react with oxygen?
they react with oxygen very vigourously at room temperature
How does calcium, magnesium, zinc, iron, copper and silver react with oxygen?
react very slowly when heated
How does gold react with oxygen?
does not react
How does sodium, lithium and calcium react with water?
they react with water
How does potassium react with water?
it burns with a lilac flame
How does copper, silver and gold react with water?
do not react
How does potassium, sodium and lithium react with acid?
they have an extremely violent reaction
How does calcium, magnesium, zinc and iron react with acid?
reacts to form salts and hydrogen gas
How does copper, silver and gold react with acid?
do not react
what is the order of the reactivity series
what are displacement reactions?
a more reactive metal can displace a less reactive metal from a compound
define oxidation
when a substance loses electrons
define reduction
when a substance gains electrons
what is a redox reaction
a reaction in which both oxidation and reduction has occurred.
how are high and medium reactivity metals found?
they are found as ‘ores’
how are low reactivity metals found?
found naturally
‘pure’ or ‘native’
How are elements that are more reactive than carbon extracted?
through electrolysis
How are elements that are less reactive than carbon extracted?
through reduction by carbon
give an example of reduction by carbon?
copper oxide + carbon –> copper + carbon dioxide
carbon has gained oxygen, while copper has lost oxygen
this is a redox reaction
metal + acid –>
salt + hydrogen
metal oxide + acid –>
salt + water
metal hydroxide + acid –>
salt + water
alkali + acid –>
salt + water
what is an alkali?
a base that can dissolve in H2O
metal carbonate + acid –>
salt + water + carbon dioxide
chloride ion
Cl-
sulphate ion
SO42-
Nitrate ion
NO3-
Describe how you can make copper sulfate crystals
- Add excess copper oxide into a beaker with sulfuric acid (this is to ensure all of the acid is reacted)
- Once reacted, filter the solution to get rid of the excess copper oxide
- Heat solution to allow the water to evaporate
- Copper sulfate crystals will start to form
- Turn off the heat and let the rest of the water evaporate
define acid
an acid dissolves in water to produce H+ ions (hydrogen)
give an example of acid dissolving in water.
HCl —> H+ + Cl-
the acid dissociated to form a hydrogen ion and leaves behind a negative ion from the acid
define alkali
an alkali dissolves in water to produce hydroxide ions (OH-)
give an example of alkali dissolving in water.
NaOH –> Na+ + OH-
the alkali dissociated to form a negative hydroxide ion and a positive metal ion from the
what is the pH scale?
a measure of how acidic or alkaline a substance is
which colours are:
most acidic
most alkaline
neutral
red: strong acid
yellow: weak acid
green: neutral
blue: weak alkali
purple: strong alkali
give a way to measure pH
universal indicator
what happens in neutralisation reactions?
in neutralisation reactions between an acid and an alkali, hydrogen ions react with hydroxide ions to produce water.
H+ + OH- —> H2O
give an example of a neutralisation reaction
HCl + NaOH —> NaCl + H2O
define strong acids
they fully dissociate into ions when they dissolve in water
there are no molecules of the original acid left, and the change is not reversible
define weak acids
they do not fully dissociate into ions when they dissolve in water
only some of the original acid molecules dissociate into ions and the change is reversible
give 2 examples of strong and weak acids
strong:
hydrochloric acid
nitric acid
weak:
ethanoic acid
citric acid
how is the pH of acids related to the concentration of H+ ions
the more H+ ions in the solution, the lower the pH
