Practice question Freshly cleaned, equal-sized pieces of metals P, Q and R are each tested at 20 °C with 10 cm³ of cold water and with 10 cm³ of 0.50 mol dm⁻³ hydrochloric acid. P fizzes with water; Q does not react with water but fizzes with the acid; R does not react with either. Deduce their order from most to least reactive.