Why is helium preferred over hydrogen for filling passenger airships?
Helium is less dense than hydrogen.
Helium is non-flammable and unreactive, making it much safer.
Helium is cheaper and easier to produce than hydrogen.
Helium is a liquid at room temperature, which helps stabilize the airship.
48 exam-style questions on OCR GCSE Chemistry Properties of materials. Each one has a worked solution and a mark scheme showing where the marks go.