(Originais Teachy 2023) - Question Medium of Sciences

In the Folha de São Paulo newspaper, on June 14, 2013, a report was published about the chemical weapons attack in Syria "[...] Sarin gas is odorless and invisible. In addition to inhalation, simple contact with the skin of this organophosphorus gas affects the nervous system and causes death by cardiopulmonary arrest. The lethal dose for an adult is half a milligram. [...] Based on the information provided and chemical concepts, approximately how many molecules are there in an approximate lethal dose of sarin gas? Given: Consider the molar mass of sarin gas to be 140 g/mol. Avogadro's constant: 6.10^{23} entities.

Imagine that you and your family went camping near a lake for the weekend. Looking at the lake, you remembered that the water there could have passed through many places and been in different forms. Think about the sun heating the lake water, it turning into vapor and rising to the sky, the clouds loaded with vapor, and then the rain falling back into the lake. Describe what happens to the water during this journey, from the lake evaporated by the sun to the rain falling back into the lake, and explain the role of the sun in the water cycle.

Ionic bonds are formed when atoms or groups of atoms transfer or share electrons, resulting in the stabilization of the system's energy by minimizing these forces between the particles involved in the chemical reaction. Which of these factors directly influence the process of ionic bonding?

In Brazil, the most frequent cancer is skin cancer, accounting for about 25% of all tumors diagnosed in all geographical regions. Natural ultraviolet radiation from the sun is its major etiological agent.