Pages 212 – 219 Date

1.Physical change = substance has its physical properties (size, shape, state) affected only 2.Chemical change = formation of new substance, properties R diff. than the original 1.Clues: energy (heat or light) is given off, or heat is absorbed 2.there is a precipitate (which means a solid has formed at the bottom of a solution) 3.the change is hard to reverse or irreversible 4.there are bubbles which means a gas is being released 5.the solution turns a different color 3.Chemical reaction = process where chemical changes occur

1.Reactants = substances that exist B4 the reaction begins 2.Products = substances that R formed from the reaction 3.The reactants & products of the reaction R shown by using a chemical equation

1.Reactants usually go on the left, then an arrow, then the products 1.Reactants & products can be separated by pluses 2.Arrow = yield sign  showing what is being produced in the reaction 3.Chemical names R used not common names 4.Word equations R nice, but long & not efficient, so chemical equations R used instead 1.Instead of using chemical names, scientists use chemical formulas 4 each substance 5.Subscripts = # of atoms of element 6.Coefficients = # of molecules (or atoms) R within the substance

BrainPOP  Balancing Equations

1.Law of conservation of mass = mass of the products is always the same as the mass of the reactants within a reaction 1.Atoms R not lost or created in a reaction 2.Just old bonds R broken & new bonds R formed 2.The amt. of atoms on the reactant side must equal the product side = balanced equation

BrainPOP  Law of Conservation of Mass

Click here for my introduction to the class on balancing equations. There are three examples given in this video. They get progressively harder each time Click here for my introduction to the class on balancing equations. There are three examples given in this video. They get progressively harder each time Click here Click here Click here for another review of balancing equations along with a review on counting atoms vs. molecules Click here for another review of balancing equations along with a review on counting atoms vs. molecules Click here Click here

1.When atoms form chemical bonds they become more stable & lower their total energy 1.So, when bonds break, energy is added 2.This energy used by the products of the reaction 2.Changes in energy R part of a reaction as new bonds form 1.Energy is either absorbed or released in any reaction

1.Endothermic reaction = energy is absorbed in the reaction 1.Think endo like enter…come in…energy in 2.Energy 2 break bonds in reactants is greater than energy to make them in products 3.Heat has to be supplied from an outside source in order for this reaction (bonds to break) 2 occur 4.This energy is sometimes written within the equation on the reactant side 2 show this

Melting ice Melting ice Heat energy is entering the H 2 O molecules in order to go from a solid to liquid Heat energy is entering the H 2 O molecules in order to go from a solid to liquid Evaporation of water Evaporation of water Baking bread Baking bread Check out this example Endothermic Chemical Definition Video

1.Exothermic reaction = energy is released in the reaction 1.Think exo like exit….energy out 2.Energy 2 break bonds in reactants is less than energy to make them in products 3.Heat is given off to the surrounding area in this reaction 4.Energy can B written on product side 2 show this 2.Energy isn’t written within the equation unless it is pertinent 2 the understanding of the equation

Ice freezing Ice freezing Condensing of rain from water vapor Condensing of rain from water vapor Exothermic Chemical Definition Video

YouTube  Endo & Exothermic Reaction Demonstrations YouTube  Exothermic Explanation plus Example