Chapter 2 Properties of Matter

Matter Pure Substances Elements Compounds Mixtures Homogenous Heterogeneous

Matter has three states Solid: Liquid Gas

Energy is related to State KINETIC ENERGY Vibrational Rotational Translational

Energy is related to state Potential Energy: Related to the position of the molecules wrt one another. Energy must be added to the system to stretch the molecules apart. Think of a rubber band.

A phase diagram is a picture of energy Changes Where there is a phase change: energy is added as potential. Where there is a temperature change: energy is added as kinetic. The total change in energy is the sum of all the energy added and/or lost

A picture of Energy A plot of DT vs DQ Temperature Energy added

High energy changes cause chemical change Interacts with matter Low energy changes cause physical change in matter Changes in state = PE Melting Evaporation Changes in temp. = KE- indicates change in motion High energy changes cause chemical change

Pure substances Matter that always has exactly the same composition is classified as a pure substance

Laws that Govern Pure Substances Law of Conservation of Mass/Energy Law of Definite Composition Law of Multiple Proportions

Conservation of Mass During a chemical reaction, the mass of the products is always equal to the mass of reactants Law of Conservation of Mass

Law of definite composition In a pure compound the elements are always combined in fixed proportions by weight Ex: water

Chemical Change = Chemical Reaction

Law of Multiple Proportions The principle that two elements that can form more than one compound combine in the ratio of small whole numbers

Law of multiple proportions

Types of Pure substances Element- simplest form of matter contains only one type of atom Compound- contains two or more elements chemically combined - can be broken down into two or more elements using chemical process

Elements And Compounds Elements are represented by symbols Compounds are represented by chemical formulas, groups of element symbols

Chemical Symbols 1st letter always upper case Each element has its own 2nd and 3rd always lower case Represents one atom (or mole) of the element

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Compounds C6H12O6

Chemical Formula – the “recipe” for a compound. Tells what elements are in the compound. Tells # of atoms of each element. Ex. H2O = 2 atoms of hydrogen and 1 atom of oxygen Ex. NaCl C6H12O6 H2SO4

Mixtures Mixture-physical blend of two or more components 2 Types: Heterogeneous Homogenous (solution)

Mixtures Heterogeneous – parts of the mixture are noticeably different form each other Homogeneous- parts of the mixture are evenly distributed

Types of Mixtures Homogeneous Heterogeneous

Physical Properties Physical property- any characteristic of a material that can be observed or measured without changing the composition of the substances viscosity Conductivity Malleability Hardness Melting point Boiling point density

Physical properties : Viscosity

Chemical properties Chemical property-any ability to produce a change in composition of matter Flammability Reactivity Toxicity Heat of combustion

Chemical properties : Reactivity Chemical reactivity- property that describes how easy it is for a substance to chemically combine with another substance Ex: oxygen – high reactivity nitrogen - low reactivity

Chemical Changes (Rxn) During a chemical change, the composition of matter always changes Reactant Product

Indicators of Chemical Change Formation of precipitate A solid that forms and separates from a mixture Production of a gas Change in pH Energy change Color change Light