Chemical Reactions

1. Chemical Reactions OGT

2. Matter • In chemical reactions - matter cannot be destroyed • In chemical reactions - matter cannot be created ________________________________________________ 1st Law of Thermodynamics Energy can be changed from one form to another, but it cannot be created or destroyed. ________________________________________________ • In chemical reactions matter is changed

3. Organizing Reactions With so many chemical reactions, scientists have found it useful to classify them into five general types: 1. Synthesis 2. Decomposition 3. Single Replacement 4. Double Replacement 5. Combustion

4. Synthesis • Synthesis reactions involve two or more substances which combine to make a more complex substance • They look like this: A + B  AB H2 + O2 H2Ounbalanced C + O2 CO2unbalanced

5. Decompositon • Decomposition reactions find one substance being broken down into two or more simpler substances • This reaction is the opposite of a synthesis reaction • They look like this: AB  A + B H2O  H2 + O2unbalanced Ag2O  Ag + O2 unbalanced

6. Single Replacement • This reaction occurs when an element trades places with another element • They look like this: A + BC  AC + B Mg + HCl  MgCl 2 + H2 unbalanced Cl2 + KBr KCl + Br2 unbalanced

7. Double Replacement • Like dancing couples, compounds in this type of reaction just exchange partners • They look like this: AB + CD  AD + CB Pb(NO3)2 + KI  PbI2 + KNO3 unbalanced H2SO4 + NaOH  Na2SO4 + H2O unbalanced

8. Combustion • These reactions occur when oxygen combines with some other compound to form H2O and CO2 C10H8 + O2H2O+CO2unbalanced C3H8 + O2 H2O + CO2unbalanced