CHEMICAL ELEMENTS - Aluminum. Bromine. Sodium. pure substances that cannot be decomposed by ordinary means to other substances.

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2 CHEMICAL ELEMENTS - pure substances that cannot be decomposed by ordinary means to other substances. Aluminum Sodium Bromine

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

4 Dmitri Mendeleev ( )

5 Discovered 8 new elements. Only living person for whom an element was named.

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

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

8 are composed of atoms and so can be decomposed to those atoms. " #$ %!& $ & '( ) are The red compound is composed of nickel (Ni) (silver) carbon (C) (black) hydrogen (H) (white) oxygen (O) (red) nitrogen (N) (blue)

9 A $ & #'# is the smallest unit of a compound that retains the chemical characteristics of the compound. Composition of molecules is given by a $ & #'!*+& *$ '! H 2 O C 8 H 10 N 4 O 2 - caffeine

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

11 Graphite layer structure of carbon atoms reflects physical properties.

12 ,$ 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 ! -./ Macroscopic Particulate H 2 O (gas, liquid, solid) Symbolic

14 ! -./ Macroscopic Particulate 2 H 2 (g) + O 2 (g) --> 2 H 2 O(g) Symbolic

15 0( $ Matter consists of atoms and molecules in motion.

16 !#& +$!#* & %) have rigid shape, fixed volume. External shape can reflect the atomic and molecular arrangement. Reasonably well understood. %1 '%) have no fixed shape and may not fill a container completely. Not well understood.!#!# expand to fill their container. Good theoretical understanding.

17 2 What are some physical properties? color melting and boiling point odor

18 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 )#( %3 - an important and useful physical property Density = mass (g) volume (cm 3) Mercury Platinum Aluminum 13.6 g/cm g/cm g/cm 3

20 Relative Densities of the Elements

21 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 ). Density = mass (g) volume (cm3)

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

23 & '%& ( 1. Get dimensions in common units mm 1cm 10 mm 2. Calculate volume in cubic centimeters. 3. Calculate the density g = 9.0 g / cm3 6.4 cm 3 = cm (9.36 cm)(7.23 cm)(0.095 cm) = 6.4 cm 3 Note only 2 significant figures in the answer!

24 Density is an %( #( %.# property of matter. does NOT depend on quantity of matter. temperature Contrast with #4#( %.# depends on quantity of matter. mass and volume. )#( %3 Styrofoam Brick

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

26 PROBLEM: Mercury (Hg) has a density of of 13.6 g/cm 3.. What is is the mass of of ml of of Hg? First, note that 1 cm 3 = 1 ml 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

27 PROBLEM: Mercury (Hg) has a density of of 13.6 g/cm 3.. What is is the mass of of ml of of Hg? 1. Convert volume to mass 95 cm g cm x 10 3 g 1 lb 454 g = 1.3 x 10 3 g 2. Convert mass (g) to mass (lb) = 2.8 lb

28 There s more? Observations!

29 2 Burning hydrogen (H 2 ) in oxygen (O 2 ) gives H 2 O.

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

31 2& 5 $ 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

32 '( %& +$ #!'*#$ #( Use SI units based on the metric system Length Mass Time Temperature Meter, m Kilogram, kg Seconds, s Celsius degrees, C kelvins,, K

33 ' 1 kilometer (km) =? meters (m) 1 meter (m) =? centimeters (cm) 1 centimeter (cm) =? millimeter (mm) 1 nanometer (nm) = 1.0 x 10-9 meter O H H distance = 9.4 x m 9.4 x cm nm

34 2 Fahrenheit Celsius Kelvin Anders Celsius Lord Kelvin (William Thomson)

35 2 Boiling point of water Fahrenheit 212 F Celsius 100 C Kelvin 373 K 180 F 100 C 100 K Freezing point of water 32 F 0 C 273 K Notice that 1 kelvin degree = 1 degree Celsius

36 2 100 o F 38 o C 311 K o F o C K

37 ' 2 kelvins Generally require temp s in in kelvins T (K) = t ( C) Body temp = 37 C = 310 K Liquid nitrogen = -196 C = 77 K