State whether the following is an example of a physical or chemical change:! 21. Burning a log: ! 22. Folding a piece of paper: ! 23. Freezing water: ! 24. Bending a copper wire. !

Consider the following reactions. (note: (s) = solid, (l) = liquid, and (g) = gas.) mg(s) + ½o2(g) → mgo(s) + 146 kcal/mole h2(g) + ½o2(g) → h2o(g), δh = -57.82 kcal/mole what type of reaction is represented by the previous two examples?

What does a complete balanced chemical equation include? a. exothermic coefficients b. endothermic coefficients c. valence electrons d. molar coefficients

In which reaction is precipitation occurring?