Beyond the answers - interesting background to this quiz

A shipwreck that scandalised France

Théodore Géricault's "The Raft of the Medusa" depicts the aftermath of the 1816 wreck of the French frigate Méduse off the coast of West Africa. The captain was an incompetent royal appointee, and the hastily built raft carried around 150 people; by the time rescue came, only a handful were alive. Géricault interviewed survivors and studied corpses in morgues to get the details right, and the finished canvas was read by many as an indictment of a careless government.

A river that belongs to one country

The Yangtze is one of the world's great rivers, and unusually for a waterway of its size it flows through a single country: China. It runs roughly 6,300 kilometres from the Tibetan Plateau to the East China Sea, draining a basin that is home to hundreds of millions of people. The Three Gorges Dam, on its middle reaches, is the largest power station in the world by installed capacity.

Sodium and its stubborn symbol

Sodium's chemical symbol is Na, which looks nothing like the English name. The symbol comes from natrium, the Latin term for the element, which is also why its salts are called sodium salts in English but carry names like natrium in many European languages. Sodium is highly reactive and never occurs alone in nature; it shows up in table salt and in the minerals of the Earth's crust.

The poison hiding in your vegetable rack

Solanine is a glycoalkaloid produced by plants in the nightshade family, and potatoes are the best-known source. It is concentrated in green skin, sprouts and eyes, which is why greened or heavily sprouted potatoes are best discarded rather than peeled. In normal culinary amounts solanine is not a concern, but the bitter taste of a green potato is the plant's own warning signal.

A mountain chain that stitches a continent together

The Andes stretch along the western edge of South America and pass through seven countries: Venezuela, Colombia, Ecuador, Peru, Bolivia, Chile and Argentina. They form the longest continental mountain range on Earth and include Aconcagua, the highest peak outside Asia. The range also shapes the climate of the continent, creating the dry coastal deserts of Peru and Chile on one side and the Amazon basin on the other.