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Properties & Changes of Matter
Unit 2
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Matter Anything with mass & volume All matter is composed of atoms
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Two Types of Matter Pure substance – definite and uniform characteristics Every sample is the same Identified by density, atomic structure, etc. Mixture – contains 2 or more pure substances Can vary in composition & properties
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Pure Substances 1. Elements – contain only one kind of atom
Monatomic – exists as single atom Diatomic – two atoms joined together
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Pure Substances 2. Compounds – Composed of more than one kind of atom
Can only be broken down by chemical means Represented by formulas
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Law of Definite Proportions
Compound is always composed of the same elements in the same proportion by mass Sodium Chloride 39.3% Na & 60.7% Cl Density, atomic structure ID
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Mixtures Contain two or more pure substances
Can be separated by physical means Homogeneous – uniform composition Often called a solution Crystal Light in water Stainless steel Fountain drinks
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More on Solutions (Homogeneous)
A solution is made by dissolving SOLUTES in a SOLVENT Water is the universal solvent Colloids – appears to be a solution but really is a heterogeneous mixture Milk, asphalt, paint
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Mixtures Heterogeneous – non-uniform composition Oil and water
Trail mix This class!
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Separating a Mixture - Distillation
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Separating a Mixture - Filtration
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Separating a Mixture - Chromatography
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Physical Properties of Matter
Conditions or qualities that can be observed or measured without changing the composition of a substance
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Examples of Physical Properties
Density – ratio of mass to volume Conductivity – ability to conduct electricity or heat Malleability – ability to be deformed without cracking State of Matter
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States of matter Solid – fixed volume & shape
Liquid – Fixed volume, takes shape of its container Gas – no fixed volume or shape Vapor – currently a gas but normally a solid or liquid Plasma – particles broken apart & charged
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States of Matter Definite Volume? Definite Shape?
Intermolecular forces (IMFs) Strong – Little molecular movement Solid YES YES Less strong – Slow molecular movement Liquid NO YES Weak – Fast molecular movement Gas NO NO
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Physical Changes Identity of substance doesn’t change
Key words - boil, freeze, melt, break, crush, tear, split, grind, cut, condense Examples Dissolving sugar in water Crushing or breaking rock Changes in state of matter
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Condense Freeze Melt Evaporate Solid Liquid Gas
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Deposition Sublimation Liquid Gas Solid
Freeze Drying = Sublimation; Skips liquid phase to allow stability & aesthetics by alter temp & pressure Solid Liquid Gas
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Physical Changes State of matter changes can also be caused by pressure Different states of matter have different energy contents
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Phase Changes of Water
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Chemical Properties of Matter
Reactivity – tendency of an element to enter into a chemical reaction
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Chemical Changes of Matter
Results in the creation of a new substance AKA a chemical reaction Represented by a chemical equation Reactants products H2O + CO2 C6H12O6 + O2
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Evidence of Chemical Changes
Evolution/production of a gas Bubbling or odor change Forming a precipitate Two clear solutions cloudy/particles Release or absorb energy Change temperature or give off light Color change in reaction system
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Chemical Changes Not easily reversed End product has new properties!
Key words – burn, rot, rust, decompose, ferment, explode, corrode
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Law of Conservation of Mass
Lavoisier In a chemical reaction, the mass of the products is equal to the mass of the reactants 223.4 g Fe g O2 g Fe2O3 Mass is not created or destroyed in ordinary reactions
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