Some Heat, Please!
Squirrels are probably well equipped to handle the cold of a snowy winter. Luckily for humans, we’ve learned to take advantage of chemistry to heat the way.
News You Can Use
- Nearly every chemical process is accompanied by the flow of heat, which itself generally leads to a change in temperature. Some transformations are endothermic and cause the surroundings to decrease in temperature. That is clearly a reaction you would want to avoid if you were cold during the winter.
- Alternatively, there are processes that are exothermic and thus increase the temperature of the surroundings. A useful example of this is the crystallization of sodium acetate from a supersaturated solution, which has been exploited commercially to produce hand warmers.
- To see the dramatic crystallization, watch this video: http://www.youtube.com/watch?v=K7iM0lu61zg
Can You Apply It?
With the links below, learn more about supersaturated solutions and exothermic processes. Then answer the following questions.
- What mass of KCl (potassium chloride) can dissolve in 100g of water at 25 °C?
- KCl doesn’t readily form supersaturated solutions. What happens to prevent the formation of supersaturated solutions?
- Name some ways to cause crystallization to occur in a supersaturated solution.
- Describe a procedure for preparing a supersaturated solution.