Beyond the answers - interesting background to this quiz

One letter, two very different elements

Phosphorus carries the symbol P, while Ph is not a chemical symbol at all. That single letter matters, because phosphorus sits directly below nitrogen in the periodic table and shares its habit of forming reactive compounds. It was first isolated from urine by the Hamburg alchemist Hennig Brand in the seventeenth century, who was reportedly searching for gold. Today it is essential in fertilisers and in the DNA and bones of every living thing.

The metal that makes blood red

Iron gives hemoglobin its colour and its purpose. Each hemoglobin molecule holds iron atoms at the centre of ring-shaped structures called heme groups, and these atoms bind oxygen in the lungs and release it in the tissues. Without enough iron, the body cannot build enough healthy red blood cells, which is why iron deficiency remains one of the most common nutritional problems worldwide.

A capital with a volcanic neighbour

Managua sits on the southern shore of Lake Xolotlan in Nicaragua and has been the country's capital since the mid-nineteenth century, apart from a brief period when the seat of government moved to Masaya. The city's position is dramatic: the Managua volcano chain lies just to the south, and earthquakes have reshaped the city more than once. Its name is thought to come from the Nahuatl term for "place beside the water".

The river that crosses a continent

The Amazon begins in the Peruvian Andes and travels roughly 6,400 kilometres before emptying into the Atlantic in Brazil. Along the way it forms part of the borders of Colombia and Peru, but Brazil holds by far the largest share of its course and of its vast drainage basin. The river's flow is so enormous that the fresh water it discharges noticeably dilutes the ocean for many kilometres offshore.

The bird that gave us a word

Ostriches are the largest living birds, standing up to about 2.7 metres tall, and they cannot fly. Their long legs, however, make them formidable runners, capable of sprinting faster than most horses over short distances. The idea that ostriches bury their heads in sand is a myth; when they lower their heads to the ground they are usually tending eggs or swallowing small stones to help grind food.