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Welcome to the World of Chemistry. The Language of Chemistry CHEMICAL ELEMENTS -CHEMICAL ELEMENTS - –pure substances that cannot be decomposed by ordinary.

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Presentation on theme: "Welcome to the World of Chemistry. The Language of Chemistry CHEMICAL ELEMENTS -CHEMICAL ELEMENTS - –pure substances that cannot be decomposed by ordinary."— Presentation transcript:

1 Welcome to the World of Chemistry

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

3 The Language of Chemistry The elements, their names, and symbols are given on the PERIODIC TABLEThe elements, their names, and symbols are given on the PERIODIC TABLE How many elements are there?How many elements are there?

4 The Periodic Table Dmitri Mendeleev ( )

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

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

7 An atom consists of a nucleusnucleus –(of protons and neutrons) electrons in space about the nucleus.electrons in space about the nucleus. The Atom Electron cloud Nucleus

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

9 A MOLECULE is the smallest unit of a compound that retains the chemical characteristics of the compound. Composition of molecules is given by a MOLECULAR FORMULA H2OH2OH2OH2O C 8 H 10 N 4 O 2 - caffeine

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

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

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

13 A Chemist’s View of Water H 2 O (gas, liquid, solid) MacroscopicMacroscopic SymbolicSymbolic ParticulateParticulate

14 A Chemist’s View 2 H 2 (g) + O 2 (g) --> 2 H 2 O(g) MacroscopicMacroscopic SymbolicSymbolic ParticulateParticulate

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.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.LIQUIDS — have no fixed shape and may not fill a container completely. –Not well understood. GASES — expand to fill their container.GASES — expand to fill their container. –Good theoretical understanding.

17 Physical Properties What are some physical properties? colorcolor melting and boiling pointmelting and boiling point odorodor

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

19 DENSITY - an important and useful physical property Mercury 13.6 g/cm g/cm 3 Aluminum 2.7 g/cm 3 Platinum

20 Relative Densities of the Elements

21 Problem A piece of copper has a mass of g. It is 9.36 cm long, 7.23 cm wide, and 0.95 mm thick. Calculate density (g/cm 3 ).

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 cm 3 Note only 2 significant figures in the answer!

24 DENSITYDENSITY Density is an INTENSIVE property of matter.Density is an INTENSIVE property of matter. –does NOT depend on quantity of matter. –temperature Contrast with EXTENSIVEContrast with EXTENSIVE –depends on quantity of matter. –mass and volume. Styrofoam Brick

25 PROBLEM: Mercury (Hg) has a density of 13.6 g/cm 3. What is the mass of 95 mL of Hg in grams? In pounds? Solve the problem using DIMENSIONAL ANALYSIS.

26 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/cm 3. What is the mass of 95 mL of Hg? First, note that 1 cm 3 = 1 mL

27 1.Convert volume to mass PROBLEM: Mercury (Hg) has a density of 13.6 g/cm 3. What is the mass of 95 mL of Hg? 2.Convert mass (g) to mass (lb)

28 There’s more? Observations!

29 Chemical Properties and Chemical Change Burning hydrogen (H 2 ) in oxygen (O 2 ) gives H 2 O.Burning hydrogen (H 2 ) in oxygen (O 2 ) gives H 2 O.

30 Chemical Properties and Chemical Change Chemical change or chemical reaction — transformation of one or more atoms or molecules into one or more different molecules.Chemical change or chemical reaction — transformation of one or more atoms or molecules into one or more different molecules. Burning hydrogen (H 2 ) in oxygen (O 2 ) gives H 2 O.Burning hydrogen (H 2 ) in oxygen (O 2 ) gives H 2 O.

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

32 UNITS OF MEASUREMENT Use SI units — based on the metric system LengthMassTimeTemperature Meter, m Kilogram, kg Seconds, s Celsius degrees, ˚C kelvins, K

33 Units of Length 1 kilometer (km) = ? meters (m)1 kilometer (km) = ? meters (m) 1 meter (m) = ? centimeters (cm)1 meter (m) = ? centimeters (cm) 1 centimeter (cm) = ? millimeter (mm)1 centimeter (cm) = ? millimeter (mm) 1 nanometer (nm) = 1.0 x meter1 nanometer (nm) = 1.0 x meter O—H distance = 9.4 x m 9.4 x cm nm O—H distance = 9.4 x m 9.4 x cm nm

34 Temperature Scales FahrenheitFahrenheit CelsiusCelsius KelvinKelvin Anders Celsius Lord Kelvin (William Thomson)

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

36 Temperature Scales 100 o F 38 o C 311 K oFoF oCoCK

37 Calculations Using Temperature Generally require temp’s in kelvinsGenerally require temp’s in kelvins T (K) = t (˚C) T (K) = t (˚C) Body temp = 37 ˚C = 310 KBody temp = 37 ˚C = 310 K Liquid nitrogen = -196 ˚C = 77 KLiquid nitrogen = -196 ˚C = 77 K Generally require temp’s in kelvinsGenerally require temp’s in kelvins T (K) = t (˚C) T (K) = t (˚C) Body temp = 37 ˚C = 310 KBody temp = 37 ˚C = 310 K Liquid nitrogen = -196 ˚C = 77 KLiquid nitrogen = -196 ˚C = 77 K


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