MATTER AND CHANGE
Chemistry: The study of matter and the changes it undergoes.
Matter Anything that has mass and takes up space
Alchemical view of matter
Matter Atoms are the building blocks of matter
Matter “Space-filling” models of molecules
Matter Oxygen Hydrogen Each element is made of the same kind of atom
Each element is made of the same kind of atom with unique set of properties
Carbon Uncut diamond Graphite Uncut diamond with impurities
STATES OF MATTER: Solid, Liquid, Gas (a) Particles in solid (b) Particles in liquid (c) Particles in gas
STATES OF MATTER SOLIDS Definite shape and volume Particles of a solid packed tightly together NOT easily compressed
SOLIDS
STATES OF MATTER LIQUIDS Particles in close contact but arrangement is not orderly or fixed Definite volume NOT easily compressed
Liquid In a liquid H2O(l) Water molecules are in constant motion there are appreciable intermolecular forces molecules are close together Liquids are almost incompressible Liquids do not fill the container some writing from Kotz (PowerPoints online) H2O(l) Water Zumdahl, Zumdahl, DeCoste, World of Chemistry 2002, page 31
STATES OF MATTER GAS Particles NOT in close contact and are constantly moving No definite volume
Some Properties of Solids, Liquids, and Gases Property Solid Liquid Gas Shape Has definite shape Takes the shape of Takes the shape the container of its container Volume Has a definite volume Has a definite volume Fills the volume of the container Arrangement of Fixed, very close Random, close Random, far apart Particles Interactions between Very strong Strong Essentially none particles
How to describe matter… Extensive properties Depends on the AMOUNT of matter in a sample Mass Volume Intensive properties Depends on the TYPE of matter in a sample Color Temperature Density
SUBSTANCE Matter that has a uniform and definite composition Every sample of a given substance has identical intensive properties because every sample has the same composition Elements CANNOT be broken down into simpler components Compounds CAN be broken down into elements
Examples of pure substances GOLD ALUMINUM
Compounds Made of two or more different kinds of elements chemically combined in a fixed proportion. for example: Common table salt is a one to one combination of sodium atoms (Na) and chlorine atoms (Cl) = NaCl
What do we mean by “chemically combined”? Elements in compounds are joined by chemical bonds. Examples of chemical bonds: Ionic bond (electrostatic attraction that binds oppositely charged ions) Usually composed of metal and nonmetal atoms Covalent bond (bond that forms by the sharing of electrons between atoms) Usually composed of carbon atoms bonded to elements such as hydrogen, oxygen, nitrogen and sulfur
Properties of Compounds Compounds can be broken down into simpler substances by chemical means but elements cannot. Compounds and the elements from which they are formed have different properties
Examples of Compounds Sugar (sucrose) Composed of carbon, hydrogen and oxygen Sugar a sweet-tasting white solid but carbon is a black, tasteless solid; Hydrogen and oxygen are odorless gasses Sugar Carbon + Water http://www.youtube.com/watch?v=A_jtOpAYG70
Sugar (sucrose)
Sugar (sucrose)
Properties of Matter Physical properties: Can be observed without changing a substance into another substance Boiling point, density, mass, volume, magnetic
Properties of Matter Physical changes Chemical changes Changes in matter that do NOT change the composition of a substance Changes of state (liquid to a gas), temperature (melting point), volume, crush, grind Chemical changes Changes that result in a new substance Combustion, oxidation, decomposition
Mixtures Physical blend of two or more components Heterogeneous = composition is variable throughout the sample Homogeneous = composition is uniform throughout the sample
Classification of Matter