Chemical Reactions Unit 5

Chemical Reactions 1 Chemical change occurs when bonds break and new bonds form New substances are produced Chemical reactions involve two main kinds of changes that you can observe Formation of new substances Precipitate- solid that is formed during a chemical reaction Changes in energy A. Endothermic- energy is absorbed B. Exothermic- energy is released

Open system-matter can enter or exit Types of Systems Open system-matter can enter or exit Closed system- matter can’t enter or exit

C +O2  CO2 Chemical Equations Chemical Equation- representation of a chemical reaction that uses symbols to show the relationship between the reactants and products Reactants- what is put into a reaction Product- what forms after a reaction occurs C +O2  CO2 Reactants Yields Product

Types of Chemical Reactions Unit 5: Chemical Reactions Types of Chemical Reactions

Synthesis Synthesis reaction- two or more substances combine to make one new compound A + B → AB

Decomposition Decomposition- single compound is broken down into two or more compounds AB → A + B

Single Replacement Reactions Single replacement- one element takes the place of another element AB + C → AC + B

AB + CD → AC + BD Double Replacement Double replacement- two substances change places with each other AB + CD → AC + BD

Combustion A compound containing carbon and hydrogen react with oxygen gas to produce carbon dioxide and water Equation: CxHx + O2 -----> CO2 + H2O

Cut and Paste Types of Chemical Reactions Tuesday November 7 Directions: Cut out the 4 types of reactions “words” and each reaction. Glue the four types of reaction words along the top of the construction paper. Sort through each reaction and glue it under the correct type. Due at the END of the period. If you don’t finish, take it home for HW. Types of Chemical reactions Quiz THURSDAY Rubric: Neatness Accuracy Following Direction

Reaction Types Lab Wednesday November 8

Counting atoms & Law of Conservation of Mass Unit 5: Chemical Reactions Counting atoms & Law of Conservation of Mass

Law of Conservation of Mass Mass is neither created nor destroyed and both sides of the equation must be equal Scientists know that there must be the same number of atoms on each side of the reaction. To balance the chemical equation, you must add coefficients in front of the chemical formulas in the equation. You cannot add or change subscripts! H2O and H2O2 are NOT the same thing! Lets WATCH: https://www.youtube.com/watch?v=3lHHOiTdmK4

Law of Conservation of Mass Article Thursday November 9, 2017 Read the Article. Write the correct answer to answers on the BACK of your visual representation. Use plenty of color in your illustration.

Numbers Subscript: small number after the symbol that tells you how many of that one element Coefficient: large number before the compound that tells you how much compound is present To find how many of each element: Multiply the coefficient by the subscript for each element

How many atoms are in each Compound? H2CO3 =___H ___C ___O H20 = ___ H ___0 HCl = ___H ___ Cl ZnCl2 = ___Zn ___Cl AgNO3 =___ Ag ___N ___O FeCl2 = ___Fe ___Cl

How many atoms are in each Compound? 2H2CO3 =___H ___C ___O 3H20 = ___ H ___0 4HCl = ___H ___ Cl 2ZnCl2 = ___Zn ___Cl 3AgNO3 =___ Ag ___N ___O 4FeCl2 = ___Fe ___Cl

Balancing Equations

Rules to balancing equations Rule 1- the superscript or the two in co2 cannot be changed Rule 2- You can add a coefficient (the three) in 3CO2 Rule 3- the atoms on both sides must be equal

Example

Let’s Practice page ___ #1 ____Mg + ____O2 --------> ____MgO Mg= Mg= O= O=

#2 ____Ca + ____O2 --------> ____CaO Ca= Ca= O= O=

#3 ____N2 + ____H2 --------> ____NH3 N= N= H= H=

#4 ____Cu2O + ____C --------> ____Cu + ____CO2 Cu= Cu= O= O= C= C=

#5 ____H2O2--------> ____H2O + _____ O2 H= H= O= O=

Balancing Equation WebQuest Wednesday November 15

Open/ Closed Lab Thursday November 16

Rate of Reaction

Energy and Reaction All chemical reactions need a certain amount of activation energy to get started. Activation energy is a certain amount of energy needed to start a chemical reaction Chemist can control rates of reactions by changing factors such as surface area, temperature and concentration Presence of a catalysts and inhibitors

Reactions Endothermic Exothermic

Rate of Reactions Increase Temperature Increase Surface area Heating a substance, it’s particles move faster Faster-moving particles increase rate reaction in two ways: Particle come in contact more often. More chances for a rxn to happen Have more energy Example: storing food in the refrigerator because keeping foods cold slows down those reactions Breaking the solid into smaller pieces, more particles are exposed and the reaction happens faster. Example: chewing food breaks it into smaller pieces that your body can digest more easily and quickly

Increase Concentration The amount of substance in a given volume Increasing concentration of reactants supplies more particles to react.

Catalysts Inhibitors Material that increases the rate of reaction by LOWERING activation energy. Controls the rate of a reaction to change the activation energy does NOT permanently changed by a reaction Material used to decease the rate of reaction Works by preventing reactants from coming together Example: preservatives added to food product to prevent them from becoming stale or spoiling

Investigating rate of reactions Wednesday November 29 LAB Investigating rate of reactions Wednesday November 29