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.

8.1 Chemical Properties and Changes chemical property chemical change dissolving

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?

Ability to Change (cont.) 8.1 Chemical Properties and Changes Ability to Change (cont.) A chemical property is the ability or inability of a substance to combine with or change into one or more new substances.

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

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

Chemical and Physical Changes 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

Forming New Substances 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.

8.1 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.

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

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

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

End of Lesson 1

8.2 Chemical Equations law of conservation of mass reactants products diatomic molecule coefficient

Is matter conserved in chemical reactions? 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.

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.

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.

Writing a Chemical Equation 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.

8.2 Chemical Equations Word Equations “Tin + oxygen → tin oxide” reads as “tin plus oxygen produces tin oxide.” Word equations can be long and do not show that mass is conserved.

Elements, Compounds, and Molecules 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.

Elements, Compounds, and Molecules (cont.) 8.2 Chemical Equations Elements, Compounds, and Molecules (cont.) Some elements are diatomic, that is, they contain two atoms. Molecules may also contain two different elements, such as hydrogen and oxygen in a water molecule.

Elements, Compounds, and Molecules (cont.) 8.2 Chemical Equations Elements, Compounds, and Molecules (cont.)

Chemical Equations Use the symbols and formulas instead of words.

Balancing a Chemical Equation 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.

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.

8.2 Chemical Equations Counting Atoms (cont.)

Writing Balanced Equations 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.

Equations for Common Chemical Reactions 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

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

Using Parentheses with Formulas 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

Which is a diatomic molecule? A O2 B H2O C CH4 D N 8.2 Chemical Equations A B C D Which is a diatomic molecule? A O2 B H2O C CH4 D N Lesson 2 Review

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

In the following equation, which is a reactant? 8.2 Chemical Equations 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 Lesson 2 Review

End of Lesson 2

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

Energy and Chemical Reactions 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.

Light From Chemical Reactions 8.3 Energy and Chemical Change Light From Chemical Reactions Some reactions give off light with almost no thermal energy. Cold light occurs at room temperature.

Conservation of Energy 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.

Chemical Bonds Molecules have chemical energy stored in their bonds. 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.

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.

Net Release of Energy (cont.) 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.

Net Release of Energy (cont.) 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.

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

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

B definite proportions C conservation of matter 8.3 Energy and Chemical Change 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 Lesson 3 Review

End of Lesson 3

Chapter Resources Menu Chapter Assessment California Standards Practice Image Bank Science Online Interactive Table Virtual Lab BrainPOP Click on a hyperlink to view the corresponding feature.

Which is a chemical change? 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 Chapter Assessment 1

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

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

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

How many (OH) molecules are in the products? Ca + 2H2O → Ca(OH)2 + H2 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 Chapter Assessment 5

A Law of Conservation of Water B Law of Conservation of Energy SCI 5.b 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 CA Standards Practice 1

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

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 CA Standards Practice 3

Which of the following is a physical change? A hydrogen burning 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 CA Standards Practice 4

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

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