Properties & Changes of Matter Unit 2

Matter Anything with mass & volume All matter is composed of atoms

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

Pure Substances 1. Elements – contain only one kind of atom Monatomic – exists as single atom Diatomic – two atoms joined together

Pure Substances 2. Compounds – Composed of more than one kind of atom Can only be broken down by chemical means Represented by formulas

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

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

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

Mixtures Heterogeneous – non-uniform composition Oil and water Trail mix This class!

Separating a Mixture - Distillation

Separating a Mixture - Filtration

Separating a Mixture - Chromatography

Physical Properties of Matter Conditions or qualities that can be observed or measured without changing the composition of a substance

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

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

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

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

Condense Freeze Melt Evaporate Solid Liquid Gas

Deposition Sublimation Liquid Gas Solid Freeze Drying = Sublimation; Skips liquid phase to allow stability & aesthetics by alter temp & pressure Solid Liquid Gas

Physical Changes State of matter changes can also be caused by pressure Different states of matter have different energy contents

Phase Changes of Water

Chemical Properties of Matter Reactivity – tendency of an element to enter into a chemical reaction

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

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

Chemical Changes Not easily reversed End product has new properties! Key words – burn, rot, rust, decompose, ferment, explode, corrode

Law of Conservation of Mass 1785 - Lavoisier In a chemical reaction, the mass of the products is equal to the mass of the reactants 223.4 g Fe + 96.0 g O2  319.4 g Fe2O3 Mass is not created or destroyed in ordinary reactions