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1. Chapter Menu Lesson 1:Chemical Properties and Changes Lesson 2:Chemical Equations Lesson 3:Energy and Chemical Change Click on a hyperlink to view the corresponding lesson.

2. 8.1 Chemical Properties and Changes chemical property chemical change dissolving

3. 8.1 Chemical Properties and Changes Ability to Change • In a chemical change, the properties that give a substance its identity change. • Properties of matter help identify objects. • Properties are either physical or chemical. What properties do elements have?

4. 8.1 Chemical Properties and Changes Chemical Properties • Examples of chemical properties include burning or rusting. • Some substances do not react.

5. 8.1 Chemical Properties and Changes Physical Properties • Physical properties can be observed without changing the substance.

6. 8.1 Chemical Properties and Changes Chemical and Physical Changes • Chemical changes change one substance into another substance. • Usually chemical changes cannot be easily reversed. Property Changes

7. 8.1 Chemical Properties and Changes Forming New Substances • All chemical changes produce substances that are different from the starting substances. • A compound is decomposed into its elements. • Two elements join to form a compound.

8. 8.1 Chemical Properties and Changes Physical Changes • A physical change is a change in which the properties of a substance change but the identity of the substance remains the same. • Dissolving is a process in which substances mix evenly with one another.

9. 8.1 Chemical Properties and Changes Lesson 1 Review • A • B • C • D Which is a chemical change? A boiling B burning C dissolving D melting

10. 8.1 Chemical Properties and Changes Lesson 1 Review • A • B • C • D Which is NOT a chemical change? Asodium metal and chlorine gas react to form salt Bsalt dissolving in water C paper burning D iron rusting

11. 8.1 Chemical Properties and Changes Lesson 1 Review • A • B • C • D Which is NOT a physical change? A melting B boiling C dissolving D burning

12. 8.2 Chemical Equations law of conservation of mass reactants products coefficient

13. 8.2 Chemical Equations Is matter conserved in chemical reactions? • Chemical equations show that in chemical reactions, atoms rearrange, but no atoms are gained or lost.

14. 8.2 Chemical Equations Antoine Lavoisier • Lavoisier invented a balance to make more precise measurements. • He also determined that the mass before and after a chemical reaction was the same.

15. 8.2 Chemical Equations Conservation of Mass • The law of conservation of mass states that the total mass before a chemical reaction is equal to the total mass after the reaction.

16. 8.2 Chemical Equations Writing a Chemical Equation • Reactants are the starting materials in a chemical reaction and are placed on the left side. • Products are the ending materials in a chemical reaction and are placed on the right side.

17. 8.2 Chemical Equations Elements, Compounds, and Molecules • Instead of writing long word equations, scientists use symbols and formulas. • Symbols represent atoms. • Formulas represent molecules. • Molecules may be elements or compounds.

18. 8.2 Chemical Equations Chemical Equations • Use the symbols and formulas instead of words.

19. 8.2 Chemical Equations Balancing a Chemical Equation • Atoms are neither gained nor lost in a reaction, so both sides of the equation must have the same number of atoms.

20. 8.2 Chemical Equations Counting Atoms • A subscript tells how many atoms of an element are in one molecule. • A coefficient tells how many atoms, molecules, or formula units are in a reaction.

21. 8.2 Chemical Equations Writing Balanced Equations Step 1 Determine the correct symbols and formulas for reactants and products. Step 2 Write reactant symbols and formulas to the left of an arrow and product symbols and formulas to the right. Step 3 Count the number of each kind of atom on both sides. Step 4 Use coefficients to make the number of each kind of atom the same on both sides of the arrow. Step 5 Check to see that each kind of atom balances.

22. 8.2 Chemical Equations Equations for Common Chemical Reactions Reaction of methane: CH4 + O2 → CO2 + H2O balance hydrogen CH4 + O2 → CO2 + 2H2O balance oxygen CH4 + 2O2 → CO2 + 2H2O

23. 8.2 Chemical Equations Equations for Common Chemical Reactions (cont.) Baking soda and vinegar: NaHCO3 + HC2H3O2 → CO2 + H2O + NaC2H3O2

24. 8.2 Chemical Equations Using Parentheses with Formulas • When counting atoms inside parentheses, the subscript multiplies all atoms inside. Ca + H2O → Ca(OH)2 + H2 Ca + 2H2O → Ca(OH)2 + H2

25. 8.2 Chemical Equations Lesson 2 Review • A • B • C • D Which is a diatomic molecule? AO2 BH2O CCH4 D N

26. 8.2 Chemical Equations Lesson 2 Review • A • B • C • D What is potassium bromide (KBr)? A an element B a mixture C a compound D a diatomic molecule

27. 8.2 Chemical Equations Lesson 2 Review • A • B • C • D In the following equation, which is a reactant? Ca +2H2O → Ca(OH)2 + H2 A H2 B (OH)2 C Ca D none of the above

28. 8.3 Energy and Chemical Change law of conservation of energy exothermic process endothermic process

29. 8.3 Energy and Chemical Change Energy and Chemical Reactions • In chemical reactions, energy is either absorbed or released. • In chemical reactions, atoms rearrange. • Rearrangement involves some form of energy, usually thermal energy.

30. 8.3 Energy and Chemical Change Conservation of Energy • Energy is stored in reacting molecules. • The law of conservation of energy states that energy cannot be created or destroyed, simply changed from one form to another.

31. 8.3 Energy and Chemical Change Chemical Bonds • Molecules have chemical energy stored in their bonds. • Energy is stored in the food that you eat and transferred to your cells.

32. 8.3 Energy and Chemical Change Net Release of Energy • When atoms rearrange, bonds are broken and new bonds form. • Breaking bonds requires energy. • Forming bonds releases energy.

33. 8.3 Energy and Chemical Change Net Release of Energy (cont.) • An exothermic process releases energy. • The products in an exothermic reaction have less energy than the reactants.

34. 8.3 Energy and Chemical Change Net Release of Energy (cont.) • An endothermic process absorbs energy. • The products in an endothermic reaction have a higher energy than the reactants.

35. 8.3 Energy and Chemical Change Lesson 3 Review • A • B Products have a higher energy level than the reactants in an endothermic reaction. A False B True

36. 8.3 Energy and Chemical Change Lesson 3 Review • A • B • C • D ____ bonds ____ energy. A Breaking; releases B Breaking; requires C Forming; requires D Ionic; release

37. 8.3 Energy and Chemical Change Lesson 3 Review • A • B • C • D The law of ____ states that energy is neither created nor destroyed in a chemical reaction. A conservation of mass B definite proportions C conservation of matter D conservation of energy

38. Chapter Assessment 1 • A • B • C • D Which is a chemical change? A copper turning green from exposure to air B drying clothes C ice melting D none of the above

39. Chapter Assessment 2 • A • B • C • D Which is a chemical property? Aboils at 100°C Bhas a volume of 500 ml C does not rust D has a luster

40. Chapter Assessment 3 • A • B • C • D Which does NOT describe an exothermic reaction? AThere is a net release of energy. BThe reactants have a higher energy than the products . CThe reactants are lower in energy than the products. D The products are less stable than the reactants.

41. Chapter Assessment 4 • A • B • C • D What is the coefficient of H2O? Ca + 2H2O → Ca(OH)2 + H2 A 1 B 0 C 4 D 2

42. Chapter Assessment 5 • A • B • C • D How many (OH) molecules are in the products? Ca + 2H2O → Ca(OH)2 + H2 A 1 B 2 C 3 D 4

43. SCI 5.b CA Standards Practice 1 • A • B • C • D In a chemical reaction, which law states the products have the same mass as the reactants? A Law of Conservation of Water B Law of Conservation of Energy C Law of Conservation of Mass D Law of Conservation of Particles

44. CA Standards Practice 2 SCI 5.c • A • B • C • D Energy is ____ in exothermic reactions. A absorbed B created C released D stored

45. CA Standards Practice 3 SCI 3.b • A • B • C • D If an equation is balanced, the number of atoms in the products is ____ the number of atoms in the reactants. A greater than B less than C equal to D none of the above

46. CA Standards Practice 4 SCI X.X • A • B • C • D Which of the following is a physical change? A hydrogen burning B iron rusting C copper turning green when exposed to air D none of the above

47. CA Standards Practice 5 SCI 3.f • A • B • C • D Symbols represent ____ and ____ represent molecules. A elements; formulas B formulas; equations C molecules; formulas D elements; equations