Sponge: Set up Cornell Notes on pg. 13 2 Sponge: Set up Cornell Notes on pg. 13 2.4 Chemical Reactions Essential Question: Hydrogen peroxide (H2O2) breaks down into water (H2O) and oxygen (O2). Explain why this is a chemical reaction. What are the reactants and products? 2.4 Chemical Reactions Hydrogen peroxide (H2O2) breaks down into water (H2O) and oxygen (O2). Explain why this is a chemical reaction. What are the reactants and products? Key Concept: Life depends on chemical reactions

When you hear the term chemical reaction, what comes to mind? On the top of pg. 12 When you hear the term chemical reaction, what comes to mind? Can you give examples of some chemical reactions?

ANSWER Maybe you think of liquids bubbling in beakers. You probably do not think of the air in your breath, but most of the carbon dioxide and water vapor that you breathe out are made by chemical reactions in your cells

KEY CONCEPT Life depends on chemical reactions.

Bonds break and form during chemical reactions. Chemical reactions change substances into different ones by breaking and forming chemical bonds Ex: iron + oxygen= rust

Bill Nye- Chemical Reactions- 3 mins

Reactants and Products Ex: Cellular Respiration Reactants and Products Reactants are the substances changed during a chemical reaction. Oxygen and Glucose Products are the substances made by a chemical reaction. Carbon Dioxide and Water Energy

6CO2 + C6H12O6 -------- 6CO2 + 6H2O Cellular Respiration 6CO2 + C6H12O6 -------- 6CO2 + 6H2O Reactants Products

Pennies Experiment Please write a hypothesis for each of the following: Hypothesis Pennies in Salt: Pennies in Water: Pennies in Vinegar: Pennies in Vinegar and Salt: Pennies in Water and Salt:

Was your hypothesis correct? Pennies in Salt: Nothing Pennies in Water: Nothing Pennies in Vinegar: Nothing Pennies in Vinegar and Salt: Pennies get cleaned!!!! Pennies in Water and Salt: Nothing Reactants: copper, vinegar, and salt Product: Hydrochloric Acid

Pg. 12- Divide into 4 sections Gummi Bear Reactants: Products: Elephant’s Toothpaste Reactants: Products: Sodium and Water Reactants: Products: Sodium and Chlorine Reactants: Products: Mentos and Diet Coke Reactants: Products: Reactants vs. Products:

On pg. 12: Name the reactants (2) and products (3) in the Gummi Bear chemical reaction. Reactants: Sucrose- Gummi Bear Molten Potassium Chlorate Products: Carbon Dioxide Water Potassium Chloride

Name the reactants and products in the “Elephant’s Toothpaste” Video Hydrogen Peroxide Liquid Soap Potassium Iodide Products O2 (oxidized) Foam Heat Name the reactants and products in the “Mentos and Diet Coke” Video Reactants Mentos Diet Coke Products CO2 Bubbles

Name the reactants and products in the “Sodium and Water” and “Sodium and Chlorine” Sodium (toxic) Chlorine (toxic) Products Sodium Chloride(Safe!!!!) aka Table Salt Reactants Sodium (toxic) Water Products Hydrogen gas and Heat!!!!

On the very bottom of pg. 12: What is the difference between reactants and products (in your own words)? Give an example of each.

Products are the substances or new things made by a chemical reaction. Answer Reactants are the substances we start with, it is what will be changed during a chemical reaction Products are the substances or new things made by a chemical reaction. Ex: Oxidized Soap Foam + heat Ex: H2O2 + liquid soap + sodium iodide

Sponge: Set up Cornell Notes on pg. 15 2 Sponge: Set up Cornell Notes on pg. 15 2.4 Chemical Reactions Essential Question: Describe how bonds break and form during chemical reactions 2.4 Chemical Reactions Describe how bonds break and reform during chemical reactions

6CO2 + C6H12O6 -------- 6CO2 + 6H2O Cellular Respiration 6CO2 + C6H12O6 -------- 6CO2 + 6H2O Reactants Products For carbon dioxide and water to be made: Bonds must be broken in the reactants Bonds must form in the products What causes these bonds to form and break???

Bond energy is the amount of energy that breaks a bond between two atoms Energy is added to break bonds. Energy is released when bonds form. Ex: Breaking up H2O molecules using electricity Ex: Forming H2O molecules

ENERGY is required to break bonds!!!! Magnet Demonstration How is bond formation represented by the snapping sound of the magnets? It represents the energy released when bonds form! How is bond breakage represented by the separation of the magnets? In order to pull the magnets apart, ENERGY is needed. ENERGY is required to break bonds!!!!

CO2 + H2O H2CO3 Chemical equilibrium A reaction is at equilibrium when reactants and products form at the same rate. CO2 + H2O H2CO3 Carbon dioxide + Water--------------Carbonic acid When the CO2 level is high in the blood, carbonic acid is formed When the CO2 level is low in the lungs, carbonic acid is broken down

All chemical reactions involve changes in energy Energy is both absorbed and released during chemical reactions Energy is added to reactants to break bonds When new bonds form in the products, energy is released

*Like the energy you would need to push a rock up a hill Activation energy is the amount of energy that needs to be absorbed to start a chemical reaction. Draw this mini picture *Like the energy you would need to push a rock up a hill

Exothermic reactions release more energy than they absorb Releases energy into its surroundings often as heat, light, or electricity Products have lower bond energy than the reactants. Reactants------- products + energy

Endothermic reactions absorb more energy than they release Absorbs energy from its surroundings in the form of heat Lowers surrounding temperature Products have a higher bond energy than the reactants

Endothermic and Exothermic: Phase Change 4 min

Endothermic Reactions Pg. 14 On the top 1/3 of pg. 14: Please make a double-bubble map comparing and contrasting exothermic reactions with endothermic reactions. Exothermic Reactions Endothermic Reactions On the middle 2/3 of pg. 14: Please take notes on the video giving examples of endothermic and exothermic reactions

Endothermic and Exothermic Reactions Clip 1min

Exothermic or Endothermic? Exo=Energy out (often as heat/light) Endo= absorbs energy

With your group: Please use the internet/book to look up two-three of each Exothermic reactions Reactants and products? Endothermic reactions

Endothermic and Exothermic Reactions Video 10 min

Involve chemical reactions Releases more energy than is absorbed Absorb more energy than is released Involve chemical reactions Excess energy released as heat or light Endothermic reactions Energy is absorbed and released Exothermic reactions Products have more bond energy than the reactants Products have lower bond energy than the reactants Involve changes in energy