A compound ion produced from carbonic acid by releasing protons.
American soldiers fought in almost all major theatres of World War II.
A colourless, odourless, non-reactive gas, it constitutes 78.1% of Earth´s atmosphere.
Colour a map with the fewest number of colours possible, so that no two adjacent regions have the same colour.
This animation demonstrates birds' bones and eggs through the example of the common blackbird.
The California Gold Rush started in 1848, near San Francisco.
Subterranean rodents widespread in Central- and Eastern Europe.
Cyclones are large air masses with winds spiralling inwards around a low-pressure centre, and carry clouds and precipitation.
Egyptian Pharaohs were respected as gods, they were lords of life and death.
Remnants of Ottoman architecture in Hungary include the Gazi Kasim Pasha Mosque in Pécs and the Minaret of Eger.
Colouring the vertices, edges and faces of a given cube according to the criteria specified in the exercise.
Colourless, odourless, heavier-than-air gas. Necessary for the photosynthesis of plants.
The Canadian helicopter is one of the most widely used helicopters in the world.
This animation demonstrates how lifts work.
This animation demonstrates how sonar works.
Pollen serves to fertilise the egg of plants. Pollen grains come in a variety of shapes and sizes, characteristic of the species.
The surface of a sphere consists of the set of points which are all at the same distance from a given point in space.
Calculating the volume of a sphere is possible using an appropriate cylinder and cone.
Maharajas were Hindu rulers of large regions of India.
Tall buildings are mementoes of human history and technological development.