Section 2: Changes in Matter Matter can undergo physical and chemical changes. K What I Know W What I Want to Find Out L What I Learned

Essential Questions What is a physical change and what are several common examples? What defines a chemical change? How can you recognize a chemical change? How does the law of conservation of mass apply to chemical reactions? Copyright © McGraw-Hill Education Changes in Matter

Good Morning! Bell Work 16 more wake-ups until Fair Day!!!! physical change phase change chemical change law of conservation of mass Changes in Matter Copyright © McGraw-Hill Education

Physical Changes A change that alters a substance without changing its composition is known as a physical change. A phase change is a transition of matter from one state to another. Boiling, freezing, melting, and condensing all describe phase changes in chemistry. Copyright © McGraw-Hill Education Changes in Matter

Chemical Changes A change that involves one or more substances turning into new substances is called a chemical change. Decomposing, rusting, exploding, burning, or oxidizing are all terms that describe chemical changes. Copyright © McGraw-Hill Education Changes in Matter

Law of Conservation of Mass The law of conservation of mass states that mass is neither created nor destroyed in a chemical reaction, it is conserved. The mass of the reactants equals the mass of the products. massreactants = massproducts Copyright © McGraw-Hill Education Changes in Matter

CONSERVATION OF MASS Problem Response KNOWN UNKNOWN mmercury(II) oxide = 10.00 g moxygen = ? g mmercury = 9.26 g Use with Example Problem 1. Problem In an experiment, 10.00 g of red mercury(II) oxide powder is placed in an open flask and heated until it is converted to liquid mercury and oxygen gas. The liquid mercury has a mass of 9.26 g. What is the mass of oxygen formed in the reaction? SOLVE FOR THE UNKNOWN State the law of conservation of mass. Massreactants = Massproducts mmercury(II) oxide = mmercury + moxygen Solve for m oxygen. moxygen = mmercury(II) oxide − mmercury Substitute mmercury(II) oxide = 10.00 g and mmercury = 9.26 g. moxygen = 10.00 g − 9.26 g moxygen = 0.74 g Response ANALYZE THE PROBLEM You are given the mass of a reactant and the mass of one of the products in a chemical reaction. According to the law of mass conservation, the total mass of the products must equal the total mass of the reactants. Changes in Matter Copyright © McGraw-Hill Education

CONSERVATION OF MASS EVALUATE THE ANSWER The sum of the masses of the two products equals the mass of the reactant, verifying that mass has been conserved. The answer is correctly expressed to the hundredths place, making the number of significant digits correct. Copyright © McGraw-Hill Education Changes in Matter

Review Essential Questions Vocabulary What is a physical change and what are several common examples? What defines a chemical change? How can you recognize a chemical change? How does the law of conservation of mass apply to chemical reactions? Vocabulary physical change phase change chemical change law of conservation of mass Copyright © McGraw-Hill Education Changes in Matter