During a chemistry demonstration, a teacher adds small, equal-sized pieces of lithium, sodium, and potassium to separate troughs of water.
Only the reaction involving potassium consistently produces a flame (which burns with a distinctive lilac colour).
Which statement best explains why a flame is produced only with potassium?
Potassium is less dense than sodium and lithium, so it floats higher in the air.
Potassium is more reactive, releasing heat energy fast enough to ignite the hydrogen gas produced.
Potassium has a higher melting point, so it does not melt and is able to catch fire as a solid.
Potassium is the only one of the three metals that reacts with water to produce a gas.
Practise Edexcel GCSE Chemistry Group 1 with exam-style questions for Foundation and Higher tier. 51 questions, matched to the Edexcel GCSE Chemistry (1CH0) specification and written in Paper 1 and Paper 2 style. Every question includes a full worked solution and mark scheme, so you can see where marks are awarded rather than just whether you got the answer right.
