TOPIC C4 CHEMICAL CHANGES Flashcards
what does the pH scale go from
0-14
pH acidity
-lower the pH of a solution, the more acidic it is
-higher the pH of a solution, the more alkaline it is
what is the neutral substance of a pH
7
e.g pure water
how to measure the pH of a solution
-indicator is a dye that changes colour depending on whether its above or below a certain pH
-named wide range indicators and are useful for estimating the pH of a solution
-pH probe attatched to the pH meter
whats an acid
-a substance that forms aqueous solution with a pH of less than 7
acids form H+ ions in water
whats a base
a substance with a pH greater than 7
whats an alkali
a base that dissolves in water to form a solution, with a pH over 7
-they form OH- in water
whats the reaction between acids and bases called
show the reaction
H+ + OH- —– H20
-NEUTRALISATION
do strong acids ionise in solutions
strong acids ionise completely in water and all acid particles dissociate to release H+ ions
do weak acids ionise
they do not fully ionise in solution
-only small proportiond of acid particles dissociate to release H+ ions
do weak acids or strong acids form reversible reactions
-reversible reactions, which sets up an equilibrium between the undissociated and undissociated acid
what does the pH mean
of an acid or alkali is the measure of the concentration of H+ ions in the solution
state the elements in the reactivity series
potassium
sodium
lithium
calcium ALL 4 VERY REACTIVE
magnesium
carbon
zinc
iron ALL 4 FAIRLY REACTIVE
hydrogen
copper 2 NOT REACTIVE
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how do metals react with acids
to produce salt and hydrogen gas
-speed of reaction is indicated by the rate of bubbles
-more reactive the metal, the faster the reaction will go
show the equation for metals reacting with water
metal + water ____ metal hydroxide +hydrogen
state what elements DO react with water and which dont
DO
-potassium
-sodium
-lithium
-calcium
DONT
-zinc
-iron
-copper
seperating metals from metal oxides
-most metals react with oxygen to form oxides and this process is an example of oxidation
-oxides are often the ores that the metals are extracted from
-a metal that seperates a metal from its oxide is a reduction reaction
Formation of metal ore
e.g magnesium
oxidation=gain of oxygen
magnesium is oxidised to make magnesium oxide
2Mg + O2 —- 2MgO
displacement meaning
where a more reactive element takes the place of a less reactive element in a compound
use of displacement
to extract a pure metal from a compound
oxidation
when a substance reacts to lose electrons
reduction
when a substance reacts to gain electrons
metal extraction
hydrogen and carbon are used to extract metals by displacement
electrolysis meaning
the method used to extract metals more reactive than carbon
