Chemical Changes and Energy
Acids and bases are everywhere in chemistry, and understanding them is crucial for your exams. Acids have a low pH because they produce H⁺ ions, while bases neutralise acids with their OH⁻ ions. The key equation to remember is: acid + base → salt + water.
When it comes to strong vs weak acids, don't confuse strength with concentration. Strong acids like hydrochloric acid (HCl) completely break apart in water, whilst weak acids like ethanoic acid only partially split up. This affects how they react, not how much acid you've got.
Electrolysis might seem tricky, but remember PANIC - Positive Anode Negative Is Cathode. Metals form positive ions and head to the negative cathode, while non-metals form negative ions and go to the positive anode. You'll need this for describing what happens during electrolysis.
Quick Tip: For electrolysis questions, always mention the ion, its charge, electrons gained/lost, and the element formed!
Energy changes split into two camps: exothermic reactions (release energy, temperature goes up) like combustion, and endothermic reactions (absorb energy, temperature drops) like dissolving. Fuel cells are brilliant because they only produce water as waste, though storing hydrogen is still a challenge.
