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Chemical Reactions. Ch.21 Sec.1. Chemical Reactions. Occurs with chemical changes Make new substances Change in which one or more substances are converted into new substances. Signs of Chemical Reactions. Change in color Release of light, heat, gas, sound, or smell.
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Chemical Reactions Ch.21 Sec.1
Chemical Reactions • Occurs with chemical changes • Make new substances • Change in which one or more substances are converted into new substances
Signs of Chemical Reactions • Change in color • Release of light, heat, gas, sound, or smell
Examples of Chemical Reactions • Growing • Ripening • Decaying • Burning • Rusting
Law of Conservation of Mass • Mass cannot be created or destroyed • Chemical reactions rearrange atoms • Break bonds, rearrange, and make new bonds • Energy breaks bonds
Chemical Equation • A way to describe a chemical reaction using chemical formulas and other symbols • Pg. 635; Table 1 and equation
Products & Reactants • Reactants = left side of equation (ALWAYS) • Products = right side of equation (ALWAYS)
Chemical Equations • Balanced chemical equation – has same number of atoms of each element on both sides of the equation • Satisfies the Law of Conservation of mass.
Reaction Types • Synthesis • Decomposition • Single Displacement • Double Displacement • Combustion
Synthesis • Combines 2 substances to make 1 compound • A + B --> AB • Blue + Red --> Purple • Na + Cl --> NaCl • 1 Product
Decomposition • Takes 1 compound and breaks it apart into 2 or more substances • AB --> A + B • H2O --> H2 + O2 • Opposite of synthesis • 1 Reactant
Single-Displacement • 1 element swaps places with another element that is in a compound • XA + B --> XB + A • B and A swapped places • ** Has 1 compound and 1 element on both sides • Ex: CuCl2 + Al --> AlCl3 + Cu
Double - Displacement • 2 compounds exchange elements with each other • AX + BY --> AY + BX • ** 2 Compounds on both sides • Ex: NaCl + AgF NaF + AgCl
Combustion • Oxygen and another compound BURN to make new products • Oxygen is ALWAYS a reactant • CO2 + H2O is ALWAYS a product • Ex: CH4 + O2 --> CO2 + H2O
Double Displacement Decomposition Single Displacement Synthesis HCl + NaOH --> H2O + NaCl NaCl --> Na + Cl2 Al + Fe2O3 --> Al2O3 + Fe P4 + O2 --> P4O10 What Type of Reaction?
2 Types Energy Reactions • Endothermic • Exothermic
Endothermic • Endo = in • Energy is taken in (absorbed) with reactants • Drops surrounding environment temp. • Ex: Photosynthesis - takes in sunlight
Exothermic • Exo = out • Energy is released or given out with products • Raises surrounding environment’s temperature • Ex: hand warmers
Exo or Endo? • Exo • Exo • Endo • Exo • Paper burning • Firecracker Exploding • Plant making its own food • Electric blanket
Reaction Rate • How fast a reaction is going • Factors on rate: • Temperature • Surface Area • Concentration • Stirring • Catalysts
Catalysts • Substance that speeds up reaction without being permanently changed • Ex: Enzymes in our stomach speed up digestion (lactose)
Inhibitors • Substance used to slow down a chemical reaction • Ex: Food preservatives (prevent spoilage) • Product is not changed just how fast or slow the rate of production occurs