1 (g-a). The Law of Conservation of Mass (matter)
A chemical reaction occurs when new kinds of matter are formed. The composition of the matter changes and the new kinds of matter have different properties from the old matter. Evidence of a chemical change may be the production or use of energy such as heat or light. The mass remains the same before the reaction and after. A chemical reaction takes place when vinegar and baking soda are mixed. One of the new substances formed is carbon dioxide gas. If the carbon dioxide gas is contained, the mass of the substances will stay the same according to the Law of Conservation of Mass. If the gas is allowed to escape, the mass will be less.