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Welcome to the World of Chemistry

Chemistry 116LFall 2009

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Welcome to the World of Chemistry

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    1. Welcome to the World of Chemistry To play the movies and simulations included, view the presentation in Slide Show Mode.To play the movies and simulations included, view the presentation in Slide Show Mode.

    5. A Chemist’s View: Exp. I

    6. Chemical Properties and Chemical Change Chemical change or chemical reaction — transformation of one or more atoms or molecules into one or more different molecules.

    7. Scientific Method (1) OBSERVE AND QUESTION about some aspect of the world. (2) POSTULATE a tentative explanation (HYPOTHESIS) and make predictions. (3) TEST those predictions against observations of reproducible events. (4) REPEAT steps 2 and 3 until there are no more discrepancies between predictions and observations. When consistency is obtained, hypotheses become a theory (i.e., a coherent set of propositions that explain a wide class of phenomena.

    8. What does Chemistry concern with ? Chemistry is the foundation of all molecular sciences Chemistry provides understanding, prediction and control of the nature and behavior of matter Chemistry is practical and profoundly philosophical HOW CAN SUBSTANCES BE MADE ? HOW DOES MATTER REACT ?! WHAT MATTER IS ?!!

    9. Chemistry & Matter Chemistry explores the MACROSCOPIC world — what we can see — to understand the PARTICULATE world we cannot see. EXPERIMENTS provide insights into these worlds beyond what our eyes can actually see!! Chem 114 students are strongly encourage to take the lab Chem 116L

    10. Types of Observations and Measurements We make QUALITATIVE observations of reactions — changes in color and physical state. We also make QUANTITATIVE MEASUREMENTS, which involve numbers. Use SI units — based on the metric system

    11. UNITS OF MEASUREMENT Use SI units — based on the metric system Length Mass Time Temperature

    12. Units of Length 1 kilometer (km) = ? meters (m) 1 meter (m) = ? centimeters (cm) 1 centimeter (cm) = ? millimeter (mm) 1 nanometer (nm) = 1.0 x 10-9 meter 1 angstrom (A) = 1.0 x 10-10 meter

    13. Temperature Scales Fahrenheit Celsius Kelvin

    14. Temperature Scales

    15. Temperature Scales

    16. Calculations Using Temperature Generally require temp’s in kelvins T (K) = t (°C) + 273.15 Body temp = 37 °C + 273 = 310 K Liquid nitrogen = -196 °C + 273 = 77 K

    17. Physical Properties What are some physical properties? color melting and boiling point odor

    18. Physical Changes Some physical changes would be boiling of a liquid melting of a solid dissolving a solid in a liquid to give a homogeneous mixture — a SOLUTION.

    19. Kinetic Nature of Matter Matter consists of atoms and molecules in motion.

    20. DENSITY - an important and useful physical property

    21. Problem A piece of copper has a mass of 57.54 g. It is 9.36 cm long, 7.23 cm wide, and 0.95 mm thick. Calculate density (g/cm3).

    22. Strategy 1. Get dimensions in common units. 2. Calculate volume in cubic centimeters. 3. Calculate the density.

    23. SOLUTION 1. Get dimensions in common units. 2. Calculate volume in cubic centimeters. 3. Calculate the density.

    24. Significant Figures

    25. DENSITY Density is an INTENSIVE property of matter. does NOT depend on quantity of matter. temperature Contrast with EXTENSIVE depends on quantity of matter. mass and volume.

    26. INVERSE PROBLEM: Mercury (Hg) has a density of 13.6 g/cm3. What is the mass of 95 mL of Hg in grams? In pounds?

    27. Strategy 1. Use density to calc. mass (g) from volume. 2. Convert mass (g) to mass (lb) Need to know conversion factor = 454 g / 1 lb PROBLEM: Mercury (Hg) has a density of 13.6 g/cm3. What is the mass of 95 mL of Hg?

    28. 1. Convert volume to mass PROBLEM: Mercury (Hg) has a density of 13.6 g/cm3. What is the mass of 95 mL of Hg?

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