Matter - Properties and Changes Chapter 3

Substances Substance = Matter that has a uniform and unchanging composition Examples are salt and water Is seawater a substance?

Properties of Matter Physical property: characteristic that can be observed or measured without changing the sample’s composition Substances have unchanging physical properties Density, color, odor, taste, hardness, melting point, boiling point, etc... Can be extensive (dependent on the amount; mass, volume, length) or intensive (independent of the amount; density)

Chemical Properties Chemical Property: The ability of a substance to combine with or change into one or more other substances

Conditions that Observations are Made Properties can be dependent on the immediate conditions Always record the conditions Pressure, temperature Think of water!

States of Matter Solid: Form of matter that has its own definite shape and volume Particles tightly packed, shape is definite, incompressible

States of Matter Liquid: Form of matter that flows, has constant volume, and takes the shape of its container Particles not rigid, particles can move past each other, virtually incompressible

States of Matter Gas: Form of matter that flows to conform to the shape of its container and fills the entire volume of its container Particles are far apart, easily compressible Vapor = gaseous state of a substance that is normally solid or liquid at room temperature Oxygen vs. water vapor?

Changes in Matter (3.2) Physical changes: altering of a substance without changing its composition Ice - water - water vapor Phase changes are physical changes boil, freeze, condense, vaporize, melt Temperatures at which substances do these are physical properties (intensive) Teacherweb.com

Chemical Changes Chemical Changes: The process that involves one or more substances changing into new substances Chemical Reaction New substances have different compositions and different properties Explode, rust, oxidize, corrode, tarnish, ferment, burn, rot Starting substances = reactants Newly formed substances = products Silvertarnishing.com

Conservation of Mass Law of Conservation of Mass: Mass is neither created nor destroyed during a chemical reaction - it is conserved Mass Reactants = Mass Products Practice Problems p. 65 6, 7

Mixtures of Matter (3.3) On the basis of composition alone, all matter can be classified into substances or mixtures Mixture = a combination of two or more pure substances in which each pure substance retains its individual chemical properties. Composition of mixtures is variable Demo

Types of Mixtures Heterogeneous: one that does not blend smoothly throughout and in which the individual substances remain distinct Sand and water, orange juice with pulp Homogeneous: one that has a constant composition throughout, it always has a single phase Salt and water, powder drink in water Called solutions

Separating Mixtures Substances in mixtures are physically combined so they can be physically separated penny and nickel mixture salt and water sand and water

Filtration Heterogeneous mixtures of solids and liquids are easily separated by filtration Uses a porous barrier to let the liquid through and traps the solids

Distillation Based on differences in boiling points of the substances in a mixture Lowest boiling point turns to a vapor first and can then be cooled and captured Homechemistry.org

Crystallization Separation technique that results in the formation of pure solid particles of a substance from a solution containing the dissolved substance Produces highly pure solids Rock Candy! crystal-clear-science-projects.com

Chromatography Separates components of a mixture on the basis of the tendency of each to travel or be drawn across the surface of another material Separate the colors of ink in a pen mason.gmu.edu

Heterogeneous Mixtures Suspensions: mixture containing particles that will settle out in left undisturbed Separate through a filter Suspended particles are large compared to other mixtures Colloids: mixture containing particles of intermediate size Cannot separate via filtration Particles big enough to scatter light (Tyndall Effect)