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CHM135H1 (52)
Chapter 1

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C.Scott Browning

Textbook Chapter 1 September-10-12 8:31 PM 1.1 Some Fundamental Definitions - Chemistry - the study of matter and its properties, the changes that matter undergoes, and the energy associated with those changes - Matter - anything with mass and volume - Composition (of matter) - the types and amounts of simpler substances that make it up - Substance - type of matter that has a defined, fixed composition - Properties (of matter) - the characteristics that give each substance its unique identity - 2 types (physical and chemical) - Physical properties: characteristics a substance shows by itself, without changing into or interacting with another substance (e.g. melting point, electrical conductivity, and density) - Physical change: substance alters its physical properties (PRESSURE CHANGE?? Changes boiling point) not its composition - Chemical properties: characteristics a substance shows as it changes into or interacts with another substance (or substances) - e.g. flammability, corrosiveness, reactivity with acids - Chemical change/reaction: occurs when a substance (or substances) is converted into a different substance (or substances) The States of Matter - Solid - fixed shape that does not conform to container shape - NOT defined by rigidity or hardness - the particles lie next to each other in a regular, 3D array - Liquid - varying shape that conforms to the container shape, but only to the extent of the liquid's volume - it has an upper surface - particles lie close together but move randomly around each other - Gas - has a varying shape that conforms to the container shape, but it fills the entire container and does NOT have a surface - particles have large distances between them and move randomly throughout the container A PHYSICAL CHANGE IS REVERSIBLE, vs. A CHEMICAL CHANGE NEEDS ANOTHER CHEMICAL REACTION (or a series of them) TO REVERSE CHEMICAL REACTION - Central theme in chemistry: macroscopic-scale properties and behaviour, those we can see, are the results of atomic-scale properties and behaviour we cannot see - We study observable changes in matter to understand their unobservable causes The Importance of Energy in the Study of Matter - Energy - the ability to do work - The total energy an object possesses is the sum of its potential and kinetic energy - Potential energy - the energy due to the position of the object relative to other objects - Kinetic energy - the energy due to the motion of the object - When energy is converted from one form to another, it is conserved, not destroyed - Situations of lower energy are more stable, and therefore favoured, over situations of higher energy (less stable) - The chemical energy of a substance results from the relative positions of and the attractions and repulsions among its particles 1.2 Chemical Arts and the Origins of Modern Chemistry - Chemistry's origin is in a prescientific past involving alchemy, medicine, and technology - Alchemy - started 1st century AD for 1500 years - influenced by Greek idea that "matter strives for perfection - alchemists obsessed with converting "baser" metals into "purer" ones (e.g. gold) - invented distillation, percolation, extraction, and devised apparatuses still used today - encouraged observation/experimentation vs. reason - Medical tradition - body is a chemical system and imbalances = illness - Technological tradition - pottery, dyeing, especially metallurgy --> contributed experience to materials - however, little interest in how or why substances transform The Phlogiston Fiasco and the Impact of Lavoisier - Chemical investigation in the modern sense began in the late 17th century - Most scientists explained combustion with the phlogiston theory - proposed combustible materials contained phlogiston (undetectable substance released when the material burns) phlogiston (undetectable substance released when the material burns) - Inconsistencies arose: why is air needed for combustion, and why does charcoal stop burning in a closed vessel? Air "attracts" phlogiston out of charcoal, and burning stops when the air in the vessel is "saturated" with phlogiston - Critics also noted that when a metal burns, it forms its calx, which weighs more than the metal - Critics: How can the loss of phlogiston cause a gain in mass? Supporters: Phlogiston has negative mass - The conflict over phlogiston was resolved by French chemist Antoine Lavoisier (1743-1794) ○ Heating mercury ca
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