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The aqueous solution of hydrogen chloride gas, known as hydrochloric acid, is a commonly used chemical in laboratories.
Vasil Levski was one of the greatest figures in Bulgarian history, a national hero and revolutionary, who played a key role in achieving Bulgaria's independence.
Chlorine is a highly reactive, toxic gas, which can be used for cleaning and disinfecting.
In this lesson you can learn about this large scavenger bird species that plays an important role in maintaining the natural habitat clean.
Learn about the life of the famous monk who played a key role in the Bulgarian National Revival.
Learn about the medieval khan who founded the First Bulgarian Empire.
Oxygen is the most abundant element in the Earth's crust; it is essential to life.
The ozone layer protects the Earth's surface from harmful ultraviolet radiation; however, the presence of ozone near the surface is dangerous.
Learn about the history of banks and their main services.
Learn about the main events and results of the French Revolution.
An unstable chemical compound consisting of hydrogen and oxygen.
How can others see me? Why cannot they spot me? These are very important questions when being on the road.
Learn about the Byzantine missionary brothers who created the first Slavic alphabet.
Learn about the Egyptian queen Cleopatra, one of the best-known women in Ancient history.
Learn about one of the most significant Bulgarian writers of the 20th century.
Learn how physicist found out that atoms are divisible.
Follow the journey of wheat from the field to the dining table.
Nitrogen comprises 78% of the air and is indispensable for living organisms.
In this lesson, you will learn about the characteristics of hydrogen sulphide.
Toxic compounds that cause acid rain and are utilised as industrial raw materials.
The most widely produced oxyacid that has a corrosive or passivating effect, depending on its concentration.
