State the colours and physical states of chlorine, bromine, and iodine at room temperature and pressure, and identify the trend in these properties going down Group VII.

Cambridge International IGCSE Chemistry (0620) — 8.3 Group VII properties · State · 4 marks · View as Markdown

Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).

Model answer (4 marks)

Chlorine – yellow‑green gas
Bromine – red‑brown liquid
Iodine – dark grey/purple‑black solid
Trend – as you go down Group VII the halogens become darker in colour and change from gas to liquid to solid; their melting and boiling points increase.

Examiner tips

Use the exact colour descriptors (yellow‑green, red‑brown, dark grey/purple‑black).
Show the sequence gas → liquid → solid and mention increasing melting/boiling points.
Keep the answer concise – one line per halogen.

Common mistakes

Using wrong colour names (e.g. green instead of yellow‑green).
Listing only the physical state without colour, or vice‑versa.

Mark scheme (4 marks)

Chlorine is a yellow-green gas at room temperature and pressure
Bromine is a red-brown / orange-brown liquid at room temperature and pressure
Iodine is a grey / dark grey / purple-black solid at room temperature and pressure
Going down Group VII the halogens become darker in colour / deeper in colour AND change from gas to liquid to solid (melting and boiling points increase)

Key terms in this question

Group VII · physical state · room temperature and pressure