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

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?

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)

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

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.

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

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.

Evolution heat or light Color change Formation of gas Precipitate Chemical Change

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

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.

Phase Changes are Changes in Position and are Physical Change

2. Chemical Properties The way a substance reacts with others to form new substances with different properties.

Chemical Properties Flamability Reactivity corrosion

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

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

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

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 ).

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.

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

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

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

Pure Substances / Mixtures Heterogeneous Mixtures Platinum Homogeneous