Carbonate ion (CO₃²⁻)

A compound ion produced from carbonic acid by releasing protons.

American soldier (World War II)

American soldiers fought in almost all major theatres of World War II.

Nitrogen (N₂) (intermediate)

A colourless, odourless, non-reactive gas, it constitutes 78.1% of Earth´s atmosphere.

Four colour theorem

Colour a map with the fewest number of colours possible, so that no two adjacent regions have the same colour.

Common blackbird

This animation demonstrates birds' bones and eggs through the example of the common blackbird.

Gold mining (19th century)

The California Gold Rush started in 1848, near San Francisco.

European ground squirrel

Subterranean rodents widespread in Central- and Eastern Europe.

Tropical cyclones

Cyclones are large air masses with winds spiralling inwards around a low-pressure centre, and carry clouds and precipitation.

Egyptian Pharaoh and his wife (2nd millennium BC)

Egyptian Pharaohs were respected as gods, they were lords of life and death.

Ottoman architecture in Hungary (17th century)

Remnants of Ottoman architecture in Hungary include the Gazi Kasim Pasha Mosque in Pécs and the Minaret of Eger.

Colouring a cube

Colouring the vertices, edges and faces of a given cube according to the criteria specified in the exercise.

Carbon dioxide (CO₂) (intermediate)

Colourless, odourless, heavier-than-air gas. Necessary for the photosynthesis of plants.

Helicopter (BELL 206 Jet Ranger)

The Canadian helicopter is one of the most widely used helicopters in the world.

Pollen

Pollen serves to fertilise the egg of plants. Pollen grains come in a variety of shapes and sizes, characteristic of the species.

Surface area of spheres (demonstration)

The surface of a sphere consists of the set of points which are all at the same distance from a given point in space.

Volume of spheres (Cavalieri´s principle)

Calculating the volume of a sphere is possible using an appropriate cylinder and cone.

Tall buildings

Tall buildings are mementoes of human history and technological development.

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