Chapter 2 Matter and Change Chemistry pg. 38

2.1 Properties of Matter Properties used to describe matter are classified as: 1. Extensive – depends on the amount of matter in a sample ex. Mass, volume 2. Intensive – depends on the type of matter in a sample, not the amount ex. Color, hardness, boiling point

Physical Property A quality or condition of a substance that can be observed or measured without changing the substance’s composition Help chemists identify substances Hardness Color Conductivity Malleability (see Table 2.1, Pg. 40)

Physical Changes Properties of a material change but the composition does not ex. Boil, freeze, melt, condense AND break, split, grind, cut, crush Physical changes can be REVERSIBLE or IRREVERSIBLE *Change of state = Reversible

Substance Matter that has a uniform and definite composition ex. Gold, copper (pure substances) Every sample has identical intensive properties because every sample has the same composition

Three states of matter Solid-definite shape, volume, not easily compressed Liquid-indefinite shape, flows, definite volume, almost incompressible Gas-indefinite shape, indefinite volume, easily compressed http://www.chem.purdue.edu/gchelp/liquids/character.html

2.2 Mixtures Physical blend of 2 or more components ex. Chicken noodle soup, air Mixtures can be classified as… HETEROGENOUS or HOMOGENOUS (based on distribution of components)

Matter can be Heterogeneous The composition is not uniform throughout More than one phase…so it’s a mixture -Phase – any region with a uniform set of properties that can be separated from each other by definite boundaries called interfaces

Matter can be Homogeneous The composition is uniform throughout, evenly distributed Only one phase

2.3 Elements and Compounds Substances classified as 1. __________- simplest form of matter that has a unique set of properties (O, H) 2. ___________- substance that contains 2 or more elements chemically combined in a fixed proportion (C6H12O6)

Compounds can be broken down by ______________ means. Elements cannot be broken down Chemical change produces matter with a different composition than the original matter Sugar Carbon + Water

Properties of Compounds Generally, properties of compounds are different from their component elements Sodium - soft, gray metal, reacts with oxygen + Chlorine - yellow-green poisonous gas Sodium chloride Reaction

Distinguishing Substances and Mixtures If the composition of a material is fixed, the material is a substance examples? If the composition of a material may vary, the material is a mixture

Classify the following Concrete __________________________ Vinegar____________________________ Carbon dioxide_____________________ Granite rock________________________ Milk________________________________

Classify the following materials as an element, compound, or mixture. a. Table salt b. Salt water c. Sodium

Symbols and Formulas Chemical symbols elements O, C, Na, Ne Chemical formulas compounds CO2 , H2O

Classifying Matter

Separating mixtures Distillation - a liquid is boiled to produce a vapor which is condensed into a liquid Other ways?

2.4 Chemical Reactions Chemical Property – the ability of a substance to undergo a specific chemical change (describes the way a substance may react to form other substances) examples? - can be observed only when a substance undergoes a chemical change

Fig. 2.13 (pg. 53) Chemical reaction S + Fe *physical - composition of matter never changes *chemical – composition of matter always changes Chemical change = chemical reaction Reactants Products

Reactants Products Chemical change = chemical reaction (one or more substances change into one or more new substances) Reactants Products

Recognizing Chemical Changes 4 Ways: 1. 2. 3. 4.

Precipitate an insoluble substance that forms in, and separates from, a solution

Identify clues for chemical changes magnesium ribbon in flame Sodium iodide solution added to mercury(II) chloride solution

Law of Conservation of Mass In any physical change or chemical reaction, mass is ________________. mass of products = mass of reactants