Predict the results of mixing halogen waters with halide solutions. Record your observations, then work out the reactivity order using the evidence. Both AQA and Edexcel Chemistry include these reactions.
Chlorine is more reactive than bromine, which is more reactive than iodine. A more reactive halogen displaces a less reactive halogen from an aqueous halide solution. Chlorine displaces bromide and iodide; bromine displaces iodide; iodine displaces neither.
Keep the physical appearances separate. Pure bromine is a red-brown liquid, but bromine dissolved in water usually looks orange. Chlorine water is pale green (sometimes nearly colourless when dilute) and iodine solutions can look yellow-brown to brown depending on concentration. The simulator uses idealised, distinctive colours and a comparison tube for each reagent.
Example: chlorine water mixed with potassium bromide develops an orange colour because bromine has been formed. The word equation is chlorine + potassium bromide → potassium chloride + bromine.
Select two reagents, predict whether displacement will take place, then test your prediction. All solutions contain only the stated chemicals. An untreated halogen-water control shows the starting colour.
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Put the halogens in reactivity order
The activity checks whether your observations are sufficient to establish the full order; a lucky guess is not enough.
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Safety and limits of the simulation
Do not attempt this experiment at home. Halogen waters can be hazardous. In a school laboratory, follow the teacher's risk assessment, eye protection and handling rules. The observations here are simplified to make displaced halogens recognisable; actual shades depend on concentrations and the solvent. A comparison tube matters when the starting reagent is already coloured.
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