bonds form in molecules of water. In both reactants and products there are four hydrogen atoms and two oxygen atoms, but the atoms are combined differently in water. Types of Chemical Reactions The chemical reaction in the Figure , in which water forms from hydrogen and oxygen, is an example of a synthesis reaction. In this type of reaction, two or more reactants combine to synthesize a single product. There are several other types of chemical reactions, including decomposition, replacement, and combustion reactions. The Table compares these four types of chemical reactions. Type of Reaction General Equation Example Synthesis A+B C 2Na + Cl2 2NaCl → → Decomposition AB A + B 2H2O + O2 → →2H2 A+BC B+ AC 2K + 2H2O 2KOH + H2 Single Replacement → → Double Replacement AB+ CD AD + CB NaCl+ AgF NaF + AgCl → → fuel + oxygen carbon dioxide + water CH4 + 2O2 CO2 + 2H2O Combustion → → Q: The burning of wood is a chemical reaction. Which type of reaction is it? A: The burning of wood—or of anything else—is a combustion reaction. In the combustion example in the table, the fuel is methane gas (CH4). Energy In and Energy Out All chemical reactions involve energy. Energy is used to break bonds in reactants, and energy is released when new bonds form in products. In terms of energy, there are two types of chemical reactions: endothermic reactions and exothermic reactions. In exothermic reactions, more energy is released when bonds form in products than is used to break bonds in reactants. These reactions release energy to the environment, often in the form of heat or light.
bonds form in molecules of water. In both reactants and products there are four hydrogen atoms and two oxygen atoms, but the atoms are combined differently in water. Types of Chemical Reactions The chemical reaction in the Figure , in which water forms from hydrogen and oxygen, is an example of a synthesis reaction. In this type of reaction, two or more reactants combine to synthesize a single product. There are several other types of chemical reactions, including decomposition, replacement, and combustion reactions. The Table compares these four types of chemical reactions. Type of Reaction General Equation Example Synthesis A+B → C 2Na + Cl2 → 2NaCl Decomposition AB → A + B 2H2O →2H2 + O2 Single Replacement A+BC → B+ AC 2K + 2H2O → 2KOH + H2 Double Replacement AB+ CD → AD + CB NaCl+ AgF → NaF + AgCl Combustion fuel + oxygen → carbon dioxide + water CH4 + 2O2 → CO2 + 2H2O Q: The burning of wood is a chemical reaction. Which type of reaction is it? A: The burning of wood—or of anything else—is a combustion reaction. In the combustion example in the table, the fuel is methane gas (CH4). Energy In and Energy Out All chemical reactions involve energy. Energy is used to break bonds in reactants, and energy is released when new bonds form in products. In terms of energy, there are two types of chemical reactions: endothermic reactions and exothermic reactions. In exothermic reactions, more energy is released when bonds form in products than is used to break bonds in reactants. These reactions release energy to the environment, often in the form of heat or light.
public_unit_2.7.1_chemical_reactions_part_2.docx