Observing Chemical Change Chapter 6 Section 1 Pg. 214-221 Reactant atoms and molecules interact to form products with different chemical properties. 5a Chemical reactions usually liberate heat or absorb heat. 5c

Intro to chemical reactions

Physical Change Chemical Change What is the difference between chemical and physical changes? Stop and Think??? Physical Change Chemical Change

Stop and Think??? Using a marshmallow give an example of a physical and a chemical change. Physical Change Chemical Change

Reaction of MgO See desktop

Magnesium reacting with Oxygen During a chemical change bonds break and new bonds form. What type of bond is this? 1 O O Magnesium reacting with Oxygen Mg + 2 Mg O 2+ 2- Reactants Products 5a 5c

Forms a Precipitate (a solid) List 4 ways to help determine that a Chemical reaction has occurred? Color Change Forms a Precipitate (a solid) Gas Formation Temp. Change 5a 5c

Chemical reaction

Energy went into breaking the bonds Endothermic Changes in Energy Breaking bonds requires energy. An endothermic reaction absorbs energy. Energy went into breaking the bonds Endothermic Energy Absorbed 5c Time

Energy was released during the formation of the bonds, Exothermic Changes in Energy Making bonds releases energy. An exothermic reaction releases energy in the form of heat. Energy was released during the formation of the bonds, Exothermic Energy Absorbed 5c Time

Overall energy was released, Exothermic Changes in Energy The formation of water from oxygen and hydrogen gas is exothermic. Overall energy was released, Exothermic Energy Absorbed 5c Time

Energy is absorbed, Endothermic Determine whether the following are examples of endothermic or exothermic change? 1. Frying an egg will turn the egg whites from a clear liquid into a white solid. Notes Energy is absorbed, Endothermic 5c

Energy is released, Exothermic Determine whether the following are examples of endothermic or exothermic change? 2. A log burning in a fireplace. Notes Energy is released, Exothermic 5c

Energy is absorbed, Endothermic Determine whether the following are examples of endothermic or exothermic change? 3. The ice pack cools instantly when squeezed causing the chemical within to react. Notes Energy is absorbed, Endothermic 5c

Video liberating/absorbing heat See desktop

Describing Chemical Reactions Chapter 6 Section 2 Pg. 224-231 Reactant atoms and molecules interact to form products with different chemical properties. 5a The idea of atoms explains the conservation of matter: in chemical reactions the number of atoms and their total mass remains the same. 5b 5c Chemical reactions usually liberate heat or absorb heat.

Iron reacts with oxygen to produce iron oxide. Chemical Equations All chemical equations use formulas or symbols to represent the substances involved in a reaction. Iron reacts with oxygen to produce iron oxide. Fe Iron 55.85 26 O Oxygen 16.00 8 2Fe + 3O  Fe O 2 3 ? ? ? ? 5a

Conservation of Matter- matter cannot be created or destroyed. In a chemical reaction, the number of atoms stays the same no matter how they are arranged. So their mass remains the same. 2Fe + 3O  Fe O 2 3 115 g 50 g 165 g Reactants Products 5a 5b

Naming and balancing

A. At least one solid product will form from ….this reaction. Two solids and two liquids are mixed together, and a chemical reaction occurs. Which of these statements must be true? Solve A. At least one solid product will form from ….this reaction. B. The two solids will form a new solid, and …. the two liquids will form a new liquid. C. None of the products will have any of the …. atoms of the reactants. D. The final result will have the same number …. and type of atoms as the reactants. 5b

Balancing Chemical Equations To describe a reaction accurately a chemical equation must show the same number of each type of atom on both sides of the equation. Write the equation 1 Mg + O  MgO 2 Count the Atoms 2 Mg + O  MgO 2 1 2 1 1 5b

Balancing Chemical Equations Use Coefficients to Balance the Atoms 3 Mg + O  MgO 2 1 2 2 2 2 Mg + O  MgO 2 1 2 Look back and Check 4 5b

Balance the equations below Solve Write the equation 1 Count the atoms 2 Use coefficients to balance the atoms 3 Look back and check 4 2 H + O  H O 2 2 4 2 2 2 4 1 2 F + NaCl  NaF + Cl 2 2 2 2 1 2 1 2 1 2 1 2 2 2 KClO  KCl + O 3 2 2 3 2 2 1 1 2 6 3 2 1 1 2 4 6 2 5b

Classifying Chemical Reactions Review -There are three general types of reactions: synthesis, decomposition, and replacement.

2 SO2 + O2 2 SO3 Classifying Chemical Reactions Synthesis Reaction NOTES When two or more elements or compounds combine to form a more complex substance, the reaction is classified as a synthesis. 2 SO2 + O2 2 SO3 5b

2 H2O + O2 2 H2O2 Classifying Chemical Reactions Decomposition Reaction NOTES Decomposition occurs when compounds break down into simpler products 2 H2O + O2 2 H2O2 5b

+ + FeS + 2 HCl FeCl2 + H2S Classifying Chemical Reactions Replacement Reaction + + NOTES When elements either replace or trade places the reaction is classified as Replacement FeS + 2 HCl FeCl2 + H2S 5b

MgO + 2HBr  MgBr2 + H2O 2N2 + 5O2  2N2O5 2Al2O3  4Al + 3O2 Determine whether the following are: synthesis, decomposition, or replacement. MgO + 2HBr  MgBr2 + H2O (Replacement) 2N2 + 5O2  2N2O5 (Synthesis) 2Al2O3  4Al + 3O2 (Decomposition) 5b