Topic 4 chemical changes definitions Flashcards
Revise (20 cards)
What is and Acid
Acids produce hydrogen ions (H+) in aqueous solutions. They have a pH range of 0-6
What is an Alkali
Alkalis produce hydroxide ions (OH-) in aqueous solutions. They have a pH range of 8-14
What is Crystallisation
A separation technique used to produce solid crystals form a solution by evaporating the solvent
Displacement
A chemical reaction in which a more reactive element displaces a less reactive element from its compound
What is Electrolysis?
The splitting of an ionic compound using electricity. the electric current is passed through a substance (electrolyte) which causes a chemical reaction and the decomposition of the materials
What is an electrolyte
A solution containing free ions from the molten or dissolved ionic substance. The ions are free to move to carry charge
What is extraction
Technique used to seperate desired substances when mixed with others
What’s a Cathode?
Negative electrode
- hydrogen produced if the metal is more reactive that hydrogen
-where positive ions gain electrons -reactions are reductions
What is Neutralisation
The reaction where an acid and a base react to form salt and water
What is oxidisation?
Gain of oxygen and/or loss of electrons
What is an anode?
Positive electrode
-where oxygen is produced unless solution contains halide ions then halogen is produced
-negatively charged ions lose electrons
-reaction are oxidations
What is a redox reaction?
A reaction where both oxidation and reduction occur simultaneously
What is reduction?
A reaction involving loss of oxygen and/or gain of electrons
What is reduction with carbons?
Metals less reactive than carbon can be extracted from their oxides by reduction with carbon
What is a strong acid?
-Completely ionised in aqueous solution
-e.g hydrochloric, nitric and sulfiric acid
What is a weak acid?
-only partially ionised in aqueous solution
-e.g. ethanoic, citric and carbonic acids
How do you test for hydrogen?
Squeaky pop test
How do you test for oxygen?
Use a glowing splint and insert it into the test tube of the gas and see if it gets re-lit
How do you test for carbon dioxide
Bubble the gas through the limewater and it should turn milky /cloudy
How do you test for chlorine?
Use damp litmus paper and if it’s put in chlorine gas it should bleach and turn white
