answer both challenge

Challenge: each person tell us in a reply a reaction that has free energy. It occurs spontaneously - no energy, heat or electricity needs to be added. Be careful, physical changes do not count. Melting or changing to a gas state is caused by adding heat. They are not examples of free energy. Similarly freezing and condensation can involve using electricity, to power a frig or ice maker, so that is not free energy example either. Challenge: Post an unique example of a concentration you came across this week, either at home in the kitchen or bathroom, or at work or school. Use only the concentrations units covered in this chapter (and formula list). Next, write a concentration formula problem for the next student to answer. Check back later to tell them if it was correct