Intensive Properties are Independent.

Transcription

1 Chapter 3: Matter- Properties and Changes Section 3.1: Properties of Matter SUBSTANCE: matter that has an uniform and unchanging composition EXAMPLES: gold, pure water, iron, aluminum PHYSICAL PROPERTIES: characteristic that can be observed or measured without changing the sample's composition EXTENSIVE PROPERTIES: depend on the amount of substance present mass, length, volume NOT EXAMPLES: salt water, Kool Aid (any mixture) INTENSIVE PROPERTIES: do not depend on the amount of substance present density, melting point, boiling point Intensive Properties are Independent. CHEMICAL PROPERTIES: the ability of a substance to combine with or change into one or more other substances To observe a chemical property, the chemical composition of the substance must change. States of Matter: all matter on Earth exists as one of three physical forms (a fourth state- plasma is recognized, but does not exist naturally on Earth except for in the form of lightning bolts, it also exists in stars and makes up about 99% of the visible universe)

2 SOLID: definite shape and volume tightly packed particles expands slightly when heated, but is incompressible (particles cannot be squeezed into a smaller volume) LIQUID: flows, constant volume, takes the shape of container particles are not held rigidly in place, less closely packed than solids particles can move past each other virtually incompressible expands slightly when heated GAS: flows to conform to shape of container and fills the entire volume of its container particles are very far apart easily compressed GAS is used to refer to a substance that is naturally in the gaseous state at room temperature (red elements among other compounds) VAPOR is used to refer to the gaseous state of a substance that is a solid or liquid at room temperature (steam, etc.) Section 3.2: Changes in Matter PHYSICAL CHANGE: alters a substance WITHOUT changing its chemical composition Rusting Iron Fe + oxygen gas --> iron oxide The iron is changed, so this a chemical change! EXAMPLES: melting, boiling, dissolving, tearing CHEMICAL CHANGE: involves one or more substances changing into new substances Melting Ice H 2 O (solid) --> H 2 O (liquid) EXAMPLES: reacting, burning, rusting The chemical composition did not change, so this is a physical change!

3 Evidence of a chemical change Formation of a solid Law of Conservation of Mass Mass is neither created nor destroyed during a chemical reaction --> it is conserved. Color Change Energy change (gives off/absorbs heat) Mass reactants = Mass products Change in odor Formation of a gas (bubbles) Example Problem: Section 3-3: Mixtures In an experiment, g of red mercury (II) oxide powder is placed in an open flask and heated until its is converted to liquid mercury and oxygen gas. The liquid mercury has a mass of 9.26 g. What is the mass of oxygen formed in the reaction? REACTANTS PRODUCTS mercury --> liquid mercury + oxygen gas g = 9.26 g +? Oxygen = g g = 0.74 g combination of two substances. Each substance maintains its unique chemical properties. 2 Types Heterogeneous: composition is not uniform EXAMPLES: Chex Mix, salsa, Italian Salad Dressing Homogeneous: uniform composition (AKA solution) EXAMPLES: salt water, Kool Aid, milk, sugar water 6 Types of Solutions 1) Gas-Gas (air) 2) Liquid-Gas (carbonated beverage) 3) Gas-Liquid (water vapor in air- humidity) 4) Solid- Liquid (Kool-aid) Ways to separate mixtures 1) Filtration (heterogeneous) 2) Distillation (homogeneous) 3) Crystallization 4) Chromatography 5) Liquid-Liquid (vinegar) 6) Solid-Solid (steel, alloy)

4 Section 3-4: Elements and Compounds Element: pure substance that cannot be separated into simpler substances by physical or chemical changes 117 total, 91 naturally occurring, rest are synthetic Periodic table: chart that organizes the elements by similar properties Group (or family): vertical columns Period: horizontal rows Diatomic 7: elements that occur as diatomic molecules Br 2 H 2 O 2 N 2 Cl 2 I 2 F 2 Compounds- two or more different elements that are chemically combined Law of Definite Proportions: a compound is always composed of the same elements in the same proportion by mass approximately 10 million known, discovery rate of 100,000 new compounds per year Carbon Dioxide: CO 2 there is always 1 C to every 2 O Formulas are written with element symbols NaCl - sodium chloride Percent by Mass = mass of the element_ x 100 mass of the compound Can be broken down into elements by chemical means A compound contains 8.44 g of carbon, 1.30 g of hydrogen, and g of oxygen. What is the percent by mass of each element? Mass of compound = 8.44 g g g = g % C = 8.44 g x 100 = 42.2% % H = 1.30 g x 100 = 6.50% g 20.00g % O = g x 100 = 51.30% 20.00g Law of Multiple Proportions: when different compounds are formed by the same combinations of elements, different masses of one element combine with the same mass of the other element in a ratio of small whole numbers CO 2 : 1 C : 2 O CO: 1 C : 1 O

5 Matter Mixtures separated by PHYSICAL methods Pure Substances Homogeneous Heterogeneous Elements Compounds separated by CHEMICAL change