LESSON 8

CHANGING MATTER AND MASS

Matter undergoes chemical reactions and changing phases. A chemical reaction is any change that involves the formation of anew substance. A chemical reaction has reactants and products. A phase change is going from solids, to liquids to gases. For example, in a mixture of ice and water, ice is the solid phase and water is the liquid phase. Water in the gaseous phase is called water vapor or steam.

Antoine Lavoisier is usually credited with introducing the law of conservation of mass in his Treatise on the Elements of Chemistyr, published in 1779. Lavoisier introduced the concept that within a closed system (in which no matter can enter or leave), the total mass of all the substances remains the same regardless of any changes in phase or chemical reactions that occur.

This law was eventually modified by Albert Einstein when he formulated the famous equation, E = mc2, which indicated that mass and energy are interchangeable (mass is a form of energy, so whenever any substance releases energy, it loses a little mass). The law of conservation of mass can be summarized simply as “Matter cannot be created or destroyed.”

The basic premise of the law of conservation of mass – you can’t get something for nothing – may seem so obvious.

Remember that mass and volume or different. Mass measure the amount of matter in the object and volume measures the amount of space occupied by a sample of matter.

Remember that when a substance melts mass is not lost, but rather a phase change occurred.

Remember that when a substance freezes the mass has not increased, the matter has expanded into a new phase – a solid.

Remember that when a substance is boiled mass is not lost, the matter has changed into a new phase.