RCD Pacing UNIT 4 PHYSICAL SCIENCE

Types of Reactions(*New Test Material) Four main types: Synthesis Decomposition Single replacement Double replacement

Decomposition AB  A + B Opposite of synthesis reaction Rxn in which a compound breaks down into 2 or more simpler substances General equation: AB  A + B Example: CaCO2  CaO + CO2

Single Replacement A + BC  B + AC Rxn in which one element takes the place of another element in a compound General equation: A + BC  B + AC Example: Cu + 2AgNO3  2Ag + Cu(NO3)2

Double Replacement AB + CD  AD + CB Rxn where 2 different compounds exchange positive ions and form two new compounds General equation: AB + CD  AD + CB Example: Pb(NO3)2 + 2 KI  PbI2 + 2KNO3

Synthesis A + B  AB -General equation: Example: 2Na + Cl2  2NaCl -Two or more substances react to form a single substance -General equation: A + B  AB Example: 2Na + Cl2  2NaCl

Combustion Reaction Combustion occurs when a hydrocarbon reacts with oxygen to produce carbon dioxide and water. CH4 + O2  CO2 + H2O

PRACTICE! Types of Chemical Reactions Worksheet 1-4 identifying. 1-10 ONLY IDENTIFY- we will work on balancing tomorrow 

Warm-Up Set 4, #1 1.___A + B  AB 2.___AB + CD  AD + CB 3.___A + BC  B + AC 4.___AB  A + B Identify the 4 equations above. Decomposition, Double Replacement, Single Replacement and Synthesis

Conservation of Mass and Energy In a reaction there are 5 grams of Carbon in the reactants. How many grams of Carbon would be in the products? 5! Why? Matter (mass) can not be created or destroyed, but it can be rearranged.

Ex. Pure Carbon burns according to the following reaction: Conservation of Mass Ex. Pure Carbon burns according to the following reaction: C + O2  CO2 CO2 is a gas, carbon is not created or destroyed, it simply changes from a solid to a gas

Rates of Reaction Don’t copy- lets talk… What makes a reaction speed up or slow down? When you eat food, do you want your energy now or later? What breaks down the food in your body to release energy?

Now YOU get to practice counting atoms! NOT FUN time!!  Math REVIEW  Guess WHAT !?!?!? Now YOU get to practice counting atoms! NOT FUN time!!  Math REVIEW 

Warm-Up Set 4, #2 1) Count the number of atoms on each side of the equation. Identify the type of reaction and try to balance it. Remember, list the elements, count and recount  CaCO2  CaO + CO2 2Na + Cl2  2NaCl

Chemistry and Energy Making a bond STORES energy. BREAKING a bond releases energy. Catalysts SPEED up the rate of a reaction.

Two types of Reactions Endothermic Reactions: Absorbs energy from its surroundings Feels “cold” to the touch

Two types of Reactions Exothermic Reactions: Releases energy to its surroundings, usually as heat. Ex. Combustion reactions

Reaction Rate The rate of a reaction tells you how fast the reaction is going. Factors that affect reaction rates include: temperature, surface area, concentration, stirring and catalysts

Demos Five ways to speed up a chemical reaction (5 minutes) Glow Stick Demo - Rates of reaction (5 minutes) Endothermic Reaction (3 minutes) Gummibear sacrifice (Exothermic Reaction) (3 minutes) Diet coke and Menthos (2 minutes)