Understanding Mass Changes in Chemical Reactions

This video discusses mass changes in chemical reactions. The Law of Conservation of Mass is introduced, which states that atoms are not lost or gained during a chemical reaction. Two examples are given: the reaction of sodium with water and the reaction of magnesium with oxygen. In the first example, hydrogen gas is formed, which escapes and causes the mass to decrease. In the second example, oxygen gas is taken on by magnesium, causing the mass to increase. The video concludes by summarizing the reasons for mass changes in reactions.