State in your own words the law of conservation of mass. State the law in its modern form.

The law of conservation of mass states that, in a closed system (i.e., when there is no exchange of matter with the surroundings), the total amount of mass remains constant. This means that the mass of the reactants in a chemical reaction equals the mass of the products.

The modern form of the law of conservation of mass takes into account the concept of energy. The total mass-energy of a closed system remains constant. This is also known as the conservation of mass-energy. In the famous equation \(E=mc^2\), Albert Einstein showed the relationship between mass and energy, where \(E\) is energy, \(m\) is mass, and \(c\) is the speed of light.

To understand the law of conservation of mass, consider the following example: Suppose we have a reaction between hydrogen gas (\(H_2\)) and oxygen gas (\(O_2\)) to form water (\(H_2O\)). The balanced chemical equation for this reaction is: \(2H_2 + O_2 \rightarrow 2H_2O\) Let's assume we have 4 grams of \(H_2\) (mass of \(H_2\)) and 32 grams of \(O_2\) (mass of \(O_2\)) as reactants. According to the law of conservation of mass, the total mass of the reactants should equal the total mass of the products. 1. Calculate the total mass of the reactants: Mass of reactants = mass of \(H_2\) + mass of \(O_2\) Mass of reactants = 4 grams + 32 grams = 36 grams 2. Carry out the reaction (in a closed system): \(2H_2 + O_2 \rightarrow 2H_2O\) 3. Determine the total mass of the products: Since the conservation of mass states that the mass of reactants equals the mass of products, the mass of 2 \(H_2O\) molecules (mass of products) should be equal to 36 grams. This example illustrates that, in a closed system, the mass of the reactants remains the same before and after a chemical reaction, fulfilling the law of conservation of mass.