Introduction to Matter

Review… What is matter? Elements, Compounds, Mixtures Classification of Matter Pure substance vs. mixture Heterogeneous vs. homogeneous mixture

Properties of Matter Physical Property: any property that is measurable whose value describes a physical system's state EXAMPLES: color, melting point, boiling point, density Chemical Property: any of a material's properties that becomes evident during a chemical reaction; that is, any quality that can be established only by changing a substance's chemical identity EXAMPLES: flammability, reactions

Chemical or Physical Property? flammability color density boiling point texture freezing point mass reactivity with acids Ability to rust solubility volume rate of decomposition

Density Ratio of mass to volume Formula: D=m/v characteristic property – does not depend on sample size varies with temperature The density of aluminum is 2.70 g/mL. If the mass of a piece of aluminum is 244 grams, what is the volume of the aluminum?

The Kinetic-Molecular Theory A scientific theory that explains the behavior of matter (KMT) atoms and molecules are constantly in motion , and we measure the energy of these movements as the temperature of that substance. This means if there is an increase in temperature, the atoms and molecules will gain more energy (kinetic energy) and move even faster. Assumptions of KMT: Matter is composed of particles Degree to which particles are spread out relates to state of matter These particles are in constant, random motion LIQUID SOLID GAS

Properties of Gases no definite shape or volume low density compressibility exert pressure have mass, take up space fluidity diffusion & effusion

Diffusion the tendency of molecules to move from an area of high concentration to an area of low concentration until the concentration is uniform throughout. Think about the water & food coloring you’ve observed…

Liquids Properties of liquids: More ordered than gases, but particles still move freely Relatively high density Relative incompressibility Ability to diffuse Surface tension

Solids Properties of solids: Types of solids: Highly ordered, particles can only vibrate around fixed points Definite shape/volume High density/incompressibility Types of solids: Crystalline Particles arranged in orderly pattern Amorphous Particles arranged randomly

Phase Changes Phase: any part of a system that has uniform composition and properties Possible Phase Changes: S  L = melting S  G = sublimation L  S = freezing L  G = evaporation (rm temp) L -> G = vaporization (heat) G  L = condensation G  S = deposition Which phase changes involve an INPUT of energy? Which phase changes involve a RELEASE of energy?

Changes in Matter Physical Change: change that does not involve a change in the identity of the substance EXAMPLES: cutting, changes of state Chemical Change: one or more substances converted into different substances EXAMPLE: Carbon + Oxygen  Carbon Dioxide

Chemical or Physical change? Sodium hydroxide dissolves in water Iron rusts A sodium pellet is sliced in two Water is heated and changed to steam Potassium chlorate decomposes to potassium chloride and oxygen gas Hydrochloric acid reacts with KOH to produce heat Sodium catches fire when placed in water Evaporation of ethanol Ice melting Milk sours Sugar dissolves in water Writing on a paper with ink Food is digested in the stomach Water is absorbed by a paper towel Tire inflated with air