1. PowerPoint Slides Shown Monday, Sept. 29 2008 CH142B

2. How to Solve Chemistry Problems 1) Problem: States all of the information needed to solve the Problem. 2) Plan: Clarify the known and unknown. Suggest the steps needed to find the solution. Develop a “roadmap” solution. 3)Solution: Calculations appear in the same order as outlined. 4) Check: Is the result what you expect or at least in the same order of magnitude! 5) Comment:Additional information as needed.

3. A Sample Problem - I International computer communications will soon be carried by optical fibers in cables laid along the ocean floor. If one strand of optical fiber weighs 1.19 x 10 -3 lbs/m, what is the total mass (in kg) of a cable made of six strands of optical fiber, each long enough to link New York and Paris? (8.85 x 10 3 km). Length (km) of Fiber Length (m) of FiberMass (lb) of FiberMass (lb) of Cable Mass (kg) of Cable 1 km = 10 3 m 1m = 1.19 x 10 -3 lb 6 fibers = 1 cable 2.205 lb = 1 kg

4. Sample Problem - II Length (m) of Fiber = 8.85 x 10 3 km x 10 3 m / km = 8.85 x 10 6 m Mass (lb) of Fiber = 8.85 x 10 6 m x 1.19 x 10 -3 lb / 1m = 1.05 x 10 4 lb Mass (lb) of cable = 1.05 x 10 4 lb / 1 fiber x 6 fibers / 1 cable = 6.30 x 10 4 lb / cable Mass (kg) of cable = 6.30 x 10 4 lb / 1 cable x 1kg / 2.205 lb = 2.86 x 10 4 kg / cable

5. A Problem on Density - I Lithium (Li) is a soft, gray solid that has the lowest density of any metal. If a slab of Li weighs 1.49 x 10 3 mg and has sides that measure 20.9 mm by 11.1 mm by 12.0 mm, what is the density of Li in g/ cm 3 ? Lengths (mm) of sides Lengths (cm) of sides Mass (mg) of Li Mass (g) of Li Density (g/cm 3 ) of Li Volume (cm 3 )

6. Density Problem - II Mass (g) of Li = 1.49 x 10 3 mg x = 1.49 g Length (cm) of one side = 20.9 mm x 1cm / 10 mm = 2.09 cm Similarly, the other side lengths are 1.11 cm and 1.20 cm Volume (cm 3 ) = 2.09 cm x 1.11 cm x 1.20 cm = 2.78 cm 3 Density of Li = = 0.536 g/cm 3 2.78 cm 3 1 g 10 3 mg 1.49 g

7. Like Problem on Density of a Metal Problem: Cesium is the most reactive metal in the periodic table, what is it’s density if a 3.4969 kg cube of Cs has sides of 125.00 mm each? Plan: Calculate the volume from the dimensions of the cube, and calculate the density from the mass and volume. Solution: Volume = (length) 3 = (12.500 cm) 3 = 1,953.125 cm 3 length = 125.00 mm = 12.500 cm density = = = 1.7904 g/ml mass = 3.4969 kg x 1000g/kg = 3,496.9 g mass 3496.9 g volume 1,953.125 cm 3

8. Temperature Scales and Interconversions Kelvin ( K ) - The “Absolute temperature scale” begins at absolute zero and only has positive values. Celsius ( o C ) - The temperature scale used by science, formally called centigrade and most commonly used scale around the world, water freezes at 0 o C, and boils at 100 o C. Fahrenheit ( o F ) - Commonly used scale in America for our weather reports, water freezes at 32 o F, and boils at 212 o F.

10. Temperature Conversions T (in K) = T (in 0 C) + 273.15 T (in 0 C) = T (in K) - 273.15 T (in 0 F) = 9/5 T (in 0 C) + 32 T (in 0 C) = [ T (in 0 F) - 32] 5/9

12. Definitions-I Matter - The “stuff” of the universe: books, planets, trees, professors - anything that has mass and volume. Composition - The types and amounts of simpler substances that make up a sample of matter. Properties - The characteristics that give each substance a unique identity. Physical Properties - are those the substance shows by itself, without interacting with another substance ( color, melting point, boiling point,density, etc.) Chemical Properties - are those that the substance shows as it interacts with, or transforms into, other substances (flammability, corrosiveness, etc.)

13. Definitions - Mass & Weight Mass - The quantity of matter an object contains kilogram - ( kg ) - the SI base unit of mass, is a platinum - iridium cylinder kept in Paris as a standard! Weight - depends upon an object’s mass and the strength of the gravitational field pulling on it.

14. Definitions - II Energy - The capacity to do work! Potential Energy - The energy due to the position of the object.Or Energy from a chemical reaction. Kinetic Energy - The energy due to the motion of the object.