What is a cough? Important knowledge about Cough.

Example with the Chemical Substance Water (H₂O):

1. Definition of H₂O:

H₂O, commonly known as water, is the most important chemical substance on Earth. This chemical comprises two hydrogen atoms (H) and one oxygen atom (O). The molecular weight of water is about 18 g/mol, calculated from the total mass of all atoms in a water molecule. Water can also exist as ions, such as in hydroxide (OH-) and hydronium (H₃O+).

2. Properties of Water:

2.1 Physical properties: Water is liquid at standard temperature and pressure, colorless, odorless, and has a pH of 7 at 25 degrees Celsius.
2.2 Chemical properties: Water has the ability to react with many other chemicals, such as alkali metals to form hydrogen and alkali salts, or react with acids to form salts and water.

3. Common Chemical Equations:

Example of water reacting with alkali metals: 2Na + 2H₂O -> 2NaOH + H₂
Example of water reacting with acids: H₂SO₄ + 2H₂O -> 2H₃O + + SO₄^2-
Example of water reacting with salts: NaCl + H₂O + H₂O -> Na + + Cl-

4. Synthesis of Water:

4.1 Synthesis of water in the laboratory: Water can be synthesized in the laboratory through the reaction between two hydrogen atoms and one oxygen atom: 2H₂ + O₂ -> 2H₂O
4.2 Synthesis of water in industrial production: Water is a by-product in many industrial processes, such as in the combustion of hydrocarbon compounds.