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Welcome to the World of Chemistry

Welcome to the World of Chemistry. The Language of Chemistry. CHEMICAL ELEMENTS - pure substances that cannot be decomposed by ordinary means to other substances. Aluminum. Bromine. Sodium. The Language of Chemistry.

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Welcome to the World of Chemistry

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  1. Welcome to the World of Chemistry

  2. The Language of Chemistry • CHEMICAL ELEMENTS - • pure substances that cannot be decomposed by ordinary means to other substances. Aluminum Bromine Sodium

  3. The Language of Chemistry • The elements, their names, and symbols are given on thePERIODIC TABLE • How many elements are there?

  4. The Periodic Table Dmitri Mendeleev (1834 - 1907)

  5. Glenn Seaborg(1912-1999 ) • Discovered 8 new elements. • Only living person for whom an element was named.

  6. Copper atoms on silica surface.See CD-ROM Screen 1.4 • An atomis the smallest particle of an element that has the chemical properties of the element. Distance across = 1.8 nanometer (1.8 x 10-9 m)

  7. Electron cloud Nucleus The Atom An atom consists of a • nucleus • (of protonsand neutrons) • electrons in space about the nucleus.

  8. The red compound is composed of• nickel (Ni) (silver)• carbon (C) (black)• hydrogen (H) (white)• oxygen (O) (red)• nitrogen (N) (blue) CHEMICAL COMPOUNDSare composed of atoms and so can be decomposed to those atoms.

  9. AMOLECULEis the smallest unit of a compound that retains the chemical characteristics of the compound. Composition of molecules is given by aMOLECULAR FORMULA C8H10N4O2 - caffeine H2O

  10. The Nature of Matter Chemists are interested in the nature of matter and how this is related to its atoms and molecules. Gold Mercury

  11. Graphite — layer structure of carbon atoms reflects physical properties.

  12. Chemistry & Matter • We can explore the MACROSCOPIC world — what we can see — • to understand the PARTICULATE worlds we cannot see. • We write SYMBOLS to describe these worlds.

  13. A Chemist’s View of Water Macroscopic H2O (gas, liquid, solid) Symbolic Particulate

  14. A Chemist’s View Macroscopic 2 H2(g) + O2 (g) --> 2 H2O(g) Particulate Symbolic

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

  16. STATES OF MATTER • SOLIDS— have rigid shape, fixed volume. External shape can reflect the atomic and molecular arrangement. • Reasonably well understood. • LIQUIDS— have no fixed shape and may not fill a container completely. • Not well understood. • GASES— expand to fill their container. • Good theoretical understanding.

  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. Platinum Mercury Aluminum DENSITY - an important and useful physical property 13.6 g/cm3 21.5 g/cm3 2.7 g/cm3

  20. Relative Densities of the Elements

  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. (9.36 cm)(7.23 cm)(0.095 cm) = 6.4 cm3 Note only 2 significant figures in the answer!

  24. PROBLEM: Mercury (Hg) has a density of 13.6 g/cm3. What is the mass of 95 mL of Hg in grams? In pounds? Solve the problem using DIMENSIONAL ANALYSIS.

  25. PROBLEM: Mercury (Hg) has a density of 13.6 g/cm3. What is the mass of 95 mL of Hg? First, note that 1 cm3 = 1 mL 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

  26. PROBLEM: Mercury (Hg) has a density of 13.6 g/cm3. What is the mass of 95 mL of Hg? 1. Convert volume to mass 2. Convert mass (g) to mass (lb)

  27. There’s more? Observations!

  28. Chemical Properties and Chemical Change • Burning hydrogen (H2) in oxygen (O2) gives H2O. • Chemical change or chemical reaction — transformation of one or more atoms or molecules into one or more different molecules.

  29. 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

  30. UNITS OF MEASUREMENT Use SI units — based on the metric system Length Mass Time Temperature Meter, m Kilogram, kg Seconds, s Celsius degrees, ˚C kelvins, K

  31. O—H distance = 9.4 x 10-11 m 9.4 x 10-9 cm 0.094 nm 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

  32. Anders Celsius 1701-1744 Lord Kelvin (William Thomson) 1824-1907 Temperature Scales • Fahrenheit • Celsius • Kelvin

  33. 212 ˚F 100 ˚C 373 K 100 K 180˚F 100˚C 32 ˚F 0 ˚C 273 K Temperature Scales Fahrenheit Celsius Kelvin Boiling point of water Freezing point of water Notice that 1 kelvin degree = 1 degree Celsius

  34. Temperature Scales 100 oF 38 oC 311 K oF oC K

  35. 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

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