Chemistry GCSE: C4 Chemical Changes Flashcards
What pHs do alkalis have?
Which pH is the most alkali?
Alkalis have pHs above (greater than) 7
pH 14 is the most alkali
What pHs do acids have?
Which pH is the most acidic?
Acids have pHs below 7
pH 0 is the most acidic
What pH is neutral?
pH7
Give two ways that you can measure the pH of a substance.
Say which is better and why?
Universal indicator or a pH probe
A probe gives a more precise (and accurate) reading.
What colour does universal indicator go in
Strong acids
Weak acids
Strong acids: Red
Weak acids: Orange/yellow
What colour does universal indicator go in
Strong alkalis
Weak alkalis
Strong alkalis: Purple
Weak alkalis: Blue
What colour does universal indicator go in
Neutral solutions
Neutral solutions: Green
What type of ions do alkalis contain
Hydroxide ions (OH-)
What type of ions do acids contain
Hydrogen ions (H+)
What is the difference between alkalis and bases?
Alkalis are bases that dissolve in water
What do we call reactions between acids and alkalis/bases?
Neutralisation reactions
Why does adding acids and alkalis/bases together lead to neutralisation?
Because the hydrogen ions react with the hydroxide ions to make water.
H+ + OH- => H2O
Metal oxides (e.g magnesium oxide) are bases. What two other types of compunds are bases?
Metal hydroxides (e.g sodium hydroxide) and metal carbonates (e.g calcium carbonate).
What two things are made when metals react with acids?
Complete this reaction: Sulfuric acid + magnesium =>
A salt and hydrogen
Sulfuric acid + magnesium => magnesium sulfate + hydrogen
What two things are made when metal oxides or metal hydroxides react with acids?
Complete this reaction: Hydrochloric acid + iron oxide =>
A salt and water
Hydrochloric acid + iron oxide => iron chloride (a salt) + water
What three things are made when metal carbonates react with acids?
Complete this reaction: Nitric acid + calcium carbonate =>
A salt, water and carbon dioxide
Nitric acid + calcium carbonate => calcium nitrate + water + carbon dioxide
What types of salts are made using hydrochloric acid?
Chlorides (e.g calcium chloride)
What types of salts are made using nitric acid?
Nitrates (e.g copper nitrate)
What types of salts are made using sulfuric acid?
Sulfates (e.g iron sulfate)
Put these metals in order or their reactivity: Potassium, magnesium, lithium, calcium, sodium.
Explain how you worked this out
Click here for the periodic table
Potassium, lithium sodium, calcium, magnesium.
Group 1 elements first (from bottom to top).
Group 2 elements next (from bottom to top)
Learn the order of reactivity of the following elements. Cover the list and see if you can remember it.
- Carbon (most reactive)
- Zinc
- Iron
- Hydrogen
- Copper (least reactive)
- Carbon (most reactive)
- Zinc
- Iron
- Hydrogen
- Copper (least reactive)
What two things are made when metals react with water?
Complete the following equation: Magnesium + water =>
Metal hydroxides and hydrogen
Magnesium + water => Magnesium hydroxide and hydrogen
Name two metals that are found as pure metals.
Why are these metals found as pure metals?
Gold and silver
Because they are very unreactive.
Most metals are not found as pure metals, they are found as metal ores. What type of compounds are metal ores.
Metal ores are metal oxides.
What two methods can be used to extract metals such as iron from their metal ores/oxides?
Displacement using carbon
Electrolysis
Why can carbon be used to extract zinc, iron and copper from their ores/oxides?
Beacuse carbon more reactive than zinc, iron, copper and so will displace them.
Why can’t carbon be used to extract aluminium from its ore/oxide?
Because carbon is less reactive than aluminium.
Why are zinc, iron and copper extracted using carbon (displacement) instead of using electrlysis?
Electrlysis is much more expensive because….
Melting metal ores uses lots of energy
Creating an electric current uses lots of energy
In electrolysis, what is the charge of the anode and what is the charge of the cathode?
PANIC
Positive Anode
Cathode Is Negtive
Whay does electrlysis mean?
What is it used for?
Using electricity (electro) to break things up (lysis).
Breaking up ionic compunds into their elements.
In what state do ionic compounds have to be for electrolysis.
Liquid/molten or aqueous/dissolved/in a solution
What does aqueous mean
It means that the substance is dissolved in water/in a solution.
In electrolysis, which electrode do the non-metal ions go to?
Explain why
Non-metal ions go to the anode (positive electrode)
Non-metals ions have a negative charge so are attracted to the positive anode.
In electrolysis, which electrode do the metal ions go to?
Explain why
Metal ions go to the cathode (negative electrode)
Metals ions have a positive charge so are attracted to the negative cathode.
In electrolysis, what happen to negative ions when they arrive at the anode (positive electrode)?
They lose electrons and are discharged as atoms or molecules.
In electrolysis, what happen to positive ions when they arrive at the cathode (negative electrode)?
They gain electrons and are discharged as atoms or molecules.
What is oxidation?
When a substance gains oxygen (e.g if carbon gains oxygen to become carbon dioxide the carbon has been oxidised).
Higher tier: When a subtance loses electrons (OIL RIG: Oxidation is loss, reduction is gain).
