4: Chemical changes

"What is oxidation (in terms of oxygen)?"

"Gain of oxygen."

"What is reduction (in terms of oxygen)?"

"Loss of oxygen."

"What do metals form when they react with oxygen?"

"Metal oxides."

"What happens to metals in oxidation reactions?"

"They gain oxygen."

"What is the reactivity of a metal related to?"

"Its tendency to form positive ions."

"What is the reactivity series?"

"A list of metals ordered by their reactivity."

"Name metals in the reactivity series from most to least reactive (common GCSE list)."

"Potassium

"What non-metals are included in the reactivity series?"

"Hydrogen and carbon."

"What happens in a displacement reaction?"

"A more reactive metal displaces a less reactive metal from its compound."

"How do metals react with water or acids?"

"More reactive metals react more vigorously and form positive ions more easily."

"How are unreactive metals like gold found?"

"As the pure metal in the Earth."

"How are metals less reactive than carbon extracted?"

"By reduction with carbon."

"What is reduction (extraction context)?"

"Loss of oxygen."

"What is oxidation (HT

electrons)?"

"What is reduction (HT

electrons)?"

"What do acids react with metals to produce?"

"Salt and hydrogen."

"Are reactions of acids with metals redox reactions (HT)?"

"Yes

"What is neutralisation?"

"Reaction of an acid with a base/alkali to produce salt and water."

"What do metal carbonates + acids produce?"

"Salt

"What determines the salt formed in neutralisation?"

"The acid used and the positive ion in the base."

"What salt is formed from hydrochloric acid?"

"Chlorides."

"What salt is formed from nitric acid?"

"Nitrates."

"What salt is formed from sulfuric acid?"

"Sulfates."

"How are soluble salts made?"

"React acid with an insoluble solid

"How do you get pure dry crystals of a salt?"

"Evaporate solution then allow to crystallise."

"What ions do acids produce in water?"

"Hydrogen ions (H+)."

"What ions do alkalis produce in water?"

"Hydroxide ions (OH-)."

"What is the pH scale range?"

"0 to 14."

"What pH is neutral?"

"7."

"What pH values do acids have?"

"Less than 7."

"What pH values do alkalis have?"

"Greater than 7."

"What happens in neutralisation at the ionic level?"

"H+ + OH- → H2O."

"What is titration used for?"

"To find exact volumes/concentrations of acids and alkalis."

"What is a strong acid?"

"Completely ionised in solution."

"What is a weak acid?"

"Partially ionised in solution."

"What happens to pH when acid strength increases?"

"pH decreases."

"What happens to H+ concentration when pH decreases by 1?"

"Increases by factor of 10."

"What does 'concentrated' mean?"

"High amount of substance in solution."

"What does 'dilute' mean?"

"Low amount of substance in solution."

"What is electrolysis?"

"Breaking down compounds using electricity."

"What is an electrolyte?"

"A liquid/solution that conducts electricity due to mobile ions."

"What happens to ions during electrolysis?"

"They move to electrodes and are discharged."

"What happens at the cathode?"

"Reduction (gain of electrons)."

"What happens at the anode?"

"Oxidation (loss of electrons)."

"What happens in electrolysis of molten compounds?"

"Metal forms at cathode

"Why is electrolysis used to extract some metals?"

"They are too reactive for carbon reduction."

"Example of electrolysis extraction?"

"Aluminium from aluminium oxide."

"Why is cryolite used in aluminium extraction?"

"Lowers melting point

"Why must the anode be replaced in aluminium extraction?"

"It reacts with oxygen and wears away."

"What forms at the cathode in aqueous electrolysis?"

"Hydrogen if metal is more reactive than hydrogen."

"What forms at the anode in aqueous electrolysis?"

"Oxygen unless halide ions present."

"What happens if halide ions are present?"

"Halogen forms at the anode."

"What are half equations?"

"Equations showing electron transfer at electrodes."

"Example half equation at cathode?"

"2H+ + 2e- → H2."

"Example half equation at anode?"

"4OH- → O2 + 2H2O + 4e-."