SWBAT: APPLY THE LAW OF CONSERVATION OF MASS TO WORD PROBLEMS SWBAT: CLASSIFY A CHANGE AS PHYSICAL OR CHEMICAL

LAW OF CONSERVATION OF MASS

WHAT DO YOU SEE? Look closely! What is its purpose? When the pans are both at the same height, what does that mean if you have masses on both pans? Keep this in mind as we continue

THE LAW The law of conservation of matter states that matter (mass) can neither be created nor destroyed. It can, however, can be rearranged. In a chemical reaction, the mass of the reactants must equal the mass of the products. HUH?

CHEMICAL EQUATIONS Because the same atoms are present in a reaction at the beginning (reactants) and at the end (products), the amount of matter in a system does not change. Law of Conservation of Matter The Law of Conservation of Matter Kotz web

CHEMICAL EQUATIONS conservation of matter Because of the principle of the conservation of matter, equation must be balanced An equation must be balanced. It must have the same number of atoms of the same kind on both sides. Lavoisier, 1788

APPLY IT! EXPERIMENT #1 Magnesium + Oxygen > Magnesium Oxide 48.6 g g -----> 80.6 g a. What is the mass of each reactant? Mg: 48.6 gO: 32.0 g b. What is the mass of the product? MgO: 80.6 g c. What is the total mass of reactants? Mg+O: 80.6 g d. Does this experimental data support the Law of Conservation of Mass? Explain. YES! The mass of the reactants and mass of the products is the same!

DESCRIBING A CHEMICAL REACTION Indications of a Chemical Reaction Evolution of heat, light, and/or sound Production of a gas Formation of a precipitate Color change

SIGNS OF CHEMICAL REACTIONS There are five main signs that indicate a chemical reaction has taken place: change in colorchange in odor production of new gases or vapor input or release of energy difficult to reverse release input

SIGNS OF PHYSICAL REACTIONS In a physical change, the substances are not altered chemically, but merely changed to another phase (i.e. gas, liquid, solid) or separated or combined. * Physical reactions are usually easily reversible!

APPLY IT! 1. Burning propane 2. Cooking 3. Breaking glass 4. Burning wood 5. Melting Ice 6. Painting wood 7. Unzipping a zipper 8. Digesting an apple 9. Lighting up a cigarette 10. Putting a plug into a socket