Unit 1: Matter – Day 29 Focus: Signs of Chemical Reactions 10-10-17 Copy this E.Q. on the next blank left-hand page in your notebook. Essential Question: What are chemical reactions, and how can I know when a chemical reaction has occurred?

Plan for Today: Notes/Discussion – Signs of Chemical Reactions 2. Lab activities – “Observing and Describing Chemical Reactions” 3. Wrap-up

Homework 1. “Evidence of chemical change” ½ sheet. 2. Chemistry exam Friday– 3. Study guide due Friday .

Notes-Evidence of Chemical Reactions Essential Question: What are chemical reactions, and how can I know when a chemical reaction has occurred?

Time to begin the next part of our unit on Matter... Chemical Reactions!

Why are chemical reactions important Why are chemical reactions important? What do they really have to do with my life? Where would you be without… Water? Digestion? Sugar? CO2? Plastics? Cake, cookies, bread? Salt?

Chemical Reactions Chemical reaction – the process by which one or more substances change to produce one or more different substances. A.D.*Chemical and physical properties of the new substances differ from the properties of the original substances. Ex: 1. change of color in Fall leaves 2.Bubbles of a gas during baking of muffins to give them a spongy texture.

Chemical Reactions Chemical reaction – the process by which one or more substances __________ to produce one or more ______________ substances. A.D.*____________ and ______________ properties of the ______ substances ________ from the properties of the ______________ substances. Ex: 1. change of ________ in Fall leaves 2.Bubbles of a _________ during _____________ of muffins to give them a __________ texture.

Signs of Chemical Reactions Gas formation *Bubbles may form (fizzing may occur) –(Alka-Seltzer in water) Solid formation (precipitate) *2 liquid substances, when combined produce a solid (or semi-solid). This is how plastics are made. 3. Energy change *energy may be given off as light or heat; temperature may increase or decrease in a reaction. Distinct color change *bleach taking out the color in fabric and other materials. *apples browning *silver tarnishing New odor produced *milk souring * garbage stinking 1 2 4 3

Signs of Chemical Reactions _____ formation *_________ may form (________ may occur) –(Alka-Seltzer in water) _________ formation (_____________) *2 _________ substances, when combined, produce a ________(or semi-solid). This is how ______________ are made. 3. __________ change *energy may be given off as _________ or ________; temperature may _____________ or __________ in a reaction. ___________ _________ change *_________taking out the color in fabric and other materials. *apples __________ *silver _________________ New _________ produced *milk __________ * garbage _____________. 1 4 3

A Change of Properties The most important sign that a chemical reaction is occurring is the formation of a new substance with new/different properties. Example: Table sugar (white, crystalline solid) reacts with sulfuric acid (clear liquid) to produce a substance that’s different than the reactants. Evidence of a reaction: gas is given off, beaker becomes very hot, distinct color change

A Change of Properties The most important sign that a chemical reaction is occurring is the formation of __________________________________________________________________ Example: Table sugar (________, crystalline solid) reacts with sulfuric acid (________ __________) to produce a substance that’s ____________ than the ______________. Evidence of a reaction: Bubbles, _______ is given off, beaker becomes very ______, distinct _______ __________.

Let’s do some lab activities to investigate some of these signs of chemical reactions. “Observing and Describing Chemical Reactions” Parts 1 and 2

Exothermic Reactions A type of reaction where energy (light, heat) is released. More energy is present during the reaction than is needed to form bonds so it’s released into the reaction environment which then feels warmer than it was before the reaction took place. A.D. Temperature increase always indicates an exothermic reaction. Exo = go out or exit *Thermic = heat or energy A.D./Ex.- glow sticks, electrical energy from batteries, light and heat (thermal energy) from a fire, cellular respiration

Exothermic Reactions A type of reaction where energy (light, heat) is _____________. _________ energy is present during the reaction than is _________ to form bonds so it’s ___________ into the reaction ____________ which then feels _________ than it was _________ the reaction took place. Temperature ____________ always indicates an ___________________ reaction. Exo = go ____ or ____ *Thermic = ____ or ______ A.D./Ex.- glow sticks, electrical energy from batteries, light and heat (thermal energy) from a fire, cellular respiration. Copy the equation for cell. resp. here.

Exothermic reaction equation: C6H12O6 + 6O2 6CO2 + 6H20 + energy (ATP) Chemical equation for cellular respiration. Energy is released. If energy is released in the form of light or heat or even chemical energy (ATP), it is an exothermic reaction.

Silver Nitrate and Potassium Iodide Precipitate Demo Silver Nitrate and Potassium Iodide

Endothermic Reactions A type of reaction where energy is taken away from the reaction environment. (The energy is needed for the reaction to take place and is stored in the bonds, therefore, the environment around the reaction feels colder.) Temperature decrease always indicates an endothermic reaction. Endo = go in Thermic = heat or energy Example is photosynthesis-here is the equation. Copy it. 6CO2 + 6H2O + energy C6H12O6 + 6O2

Endothermic Reactions A type of reaction where energy is ___________________________________________________________________________. (The energy is _________ for the reaction to take place and is __________ in the bonds, therefore, the _____________ around the reaction feels ___________.) Temperature ________________always indicates an _______________ reaction. Endo = go ___ Thermic = _____ or ______ Example is _______________-Copy the equation here.

Finish your lab questions.

Wrap-up: What signs/evidence of chemical reactions did you observe in the labs today?