General, Organic, and Biological ChemistryCopyright © 2010 Pearson Education, Inc. Review 1 Explain why Northern Europe has an avg temp of 12 ºF in February, but Northern Canada has a temp of -16 ºF.

General, Organic, and Biological ChemistryCopyright © 2010 Pearson Education, Inc. Review  Water has a high heat capacity. So even though Canada and Europe receive the same amount of sun, the warm water of the Gulf Stream holds much of its internal energy long enough to reach the coast of Europe. It releases its energy and the warm wind is carried over the land. 2

General, Organic, and Biological ChemistryCopyright © 2010 Pearson Education, Inc. Thermal Expansion 3

General, Organic, and Biological ChemistryCopyright © 2010 Pearson Education, Inc. Thermal expansion - refers to the spreading out of particles in a substance as the temperature increases Atoms are in constant motion = 1) Vibration increases with an increase in temperature 2) Space increases with an increase in temperature 4

General, Organic, and Biological ChemistryCopyright © 2010 Pearson Education, Inc. There are 2 types of expansion  Linear  Volume 5

General, Organic, and Biological ChemistryCopyright © 2010 Pearson Education, Inc. Thermal Expansion Almost all materials take up more space when heated (expansion) and less space when cooled (contraction) 6

General, Organic, and Biological ChemistryCopyright © 2010 Pearson Education, Inc. Bimetallic Strips- lower metal expands more than upper strip Two strips of iron and brass are welded together become more or less curved b/c the metals have different values for their coefficient of linear expansion They are often used as thermostats….when the room is too hot, coil bends toward iron and opens circuit 7

General, Organic, and Biological ChemistryCopyright © 2010 Pearson Education, Inc. Other applications  Heat resistant glass  Gas in a gas tank  Dental fillings  Wires on telephone poles 8

General, Organic, and Biological ChemistryCopyright © 2010 Pearson Education, Inc. Thermal Expansion…the exception 9

General, Organic, and Biological ChemistryCopyright © 2010 Pearson Education, Inc. Water expands as it cools -the ice remains on the surface since ice is less dense than water (0.917 g/mL). - Without this peculiar but wonderful property of water, life on this planet may not have been possible because the body of water would have frozen from bottom up destroying all animal and plant life. 10

General, Organic, and Biological ChemistryCopyright © 2010 Pearson Education, Inc. Review 1)Why is it important to protect water pipes in the winter, so they don’t freeze? 2)On a hot day, you remove a chilled watermelon and chilled sandwiches from a cooler, which stays cooler longer? Why? 3)If you take a bite of hot pizza, the sauce may burn your mouth, but the crust at the same temp will not…why? 11