Big Time Review Kuberg

Independent vs. Dependent Independent Variable – This is the number or item you have; the number you are measuring Independent Variable – located on the x-axis TIME IS INDEPENDENT Dependent Variable – This is the number you need to find; the outcome Dependent Variable – located on the y-axis SPEED IS DEPENDENT

Physical Changes Texture Color Temperature Shape Change of State (Boiling Point and Melting Point are significant factors in determining this change.)

Physical Properties Luster Malleability – Ability to bend Ductility - Ability to be drawn into a thin wire Density Viscosity Solubility Mass Volume 

Chemical Changes Change in Temperature Change in Color Noticeable Odor (after reaction has begun) Formation of a Precipitate Formation of Bubbles

Indicators of chemical reactions Emission of light or heat Formation of a gas Formation of a precipitate Color change Emission of odor

Chemistry

Atom Protons Neutrons Electrons Positively Charged Particles Found in Nucleus Equals Atomic Number Neutrons Neutral Charged Particles (No Charge) Found in Nucleus Electrons Negatively Charged Particles Found outside of Nucleus

Electron Shells Number of Protons = Number of Electrons Electrons vary in the amount of energy they possess, and they occur at certain energy levels or electron shells. Electron shells determine how an atom behaves when it encounters other atoms

Octet Rule = atoms tend to gain, lose or share electrons so as to have 8 electrons C would like to N would like to O would like to Gain 4 electrons Gain 3 electrons Gain 2 electrons

Electron Dot Structures Symbols of atoms with dots to represent the valence-shell electrons 1 2 13 14 15 16 17 18 H He:            Li Be  B   C   N   O  : F  :Ne :                    Na Mg  Al  Si  P S :Cl  :Ar :        

Diatomic elements There are 8 elements that never want to be alone. They form diatomic molecules. H2 , N2 , O2 , F2 , Cl2 , Br2 , I2 , and At2 The –ogens and the –ines 1 + 7 pattern on the periodic table

Chemical Bonds

Types of Chemical Bonds Ionic bonds – Metal and Non-Metal Covalent bonds – Non-Metal Metallic bonds - Metal

Ionic Bond Between atoms of metals and nonmetals with very different electronegativity Bond formed by transfer of electrons Produce charged ions all states. Conductors and have high melting point. Examples; NaCl, CaCl2, K2O

Formation of Ions from Metals Ionic compounds result when metals react with nonmetals Metals lose electrons to match the number of valence electrons of their nearest noble gas Positive ions form when the number of electrons are less than the number of protons Group 1 metals  ion 1+ Group 2 metals  ion 2+ Group 13 metals  ion 3+

Formation of Sodium Ion Sodium atom Sodium ion Na  – e  Na + 2-8-1 2-8 ( = Ne) 11 p+ 11 p+ 11 e- 10 e- 0 1+

Formation of Magnesium Ion Magnesium atom Magnesium ion  Mg  – 2e  Mg2+ 2-8-2 2-8 (=Ne) 12 p+ 12 p+ 12 e- 10 e- 0 2+

Covalent Bond Between nonmetallic elements of similar electronegativity. Formed by sharing electron pairs Stable non-ionizing particles, they are not conductors at any state Examples; O2, CO2, C2H6, H2O, SiC

2. Covalent bonds- Two atoms share one or more pairs of outer-shell electrons. Oxygen Atom Oxygen Atom Oxygen Molecule (O2)

Metallic Bond Formed between atoms of metallic elements Electron cloud around atoms Good conductors at all states, lustrous, shiny, very high melting points Examples; Na, Fe, Al, Au, Co

Metals Form Alloys Metals do not combine with metals. They form Alloys which is a solution of a metal in a metal. Examples are steel, brass, bronze and pewter.

C2H4 + 3O2 -> 2CO2 + 2H2O This is a chemical equation. C2H4 + 3O2 - These are the reactants. 2CO2 + 2H2O – These are the products. C2H4 + 3O2 -> 2CO2 + 2H2O – The #s in red are the coefficients. These can be changed to balance the equation. C2H4 + 3O2 -> 2CO2 + 2H2O - The #s in red are the subscripts. These balance the compound and cannot be changed.

Synthesis Reactions Mg3N2 (s) A + B ® AB Na (s) + Cl2 (g) ® NaCl (s) Also called combination reactions 2 elements, or compounds combine to make one compound. A + B ® AB Na (s) + Cl2 (g) ® NaCl (s) Ca (s) +O2 (g) ® CaO (s) SO3 (s) + H2O (l) ® H2SO4 (s) We can predict the products if they are two elements. Mg (s) + N2 (g) ® Mg3N2 (s)

Chemical Reactions

A simulation of the reaction: 2H2 + O2 ® 2H2O

Decomposition Reactions decompose = fall apart one compound (reactant) falls apart into two or more elements or compounds. Usually requires energy AB ® A + B NaCl Na + Cl2 CaCO3 CaO + CO2

Decomposition Reactions If the compound has more than two elements you must be given one of the products The other product will be from the missing pieces NiCO3 (aq) H2CO3(aq) ® CO2 (g) + Ni (s) H2 (g) + CO2 (g)

Single Replacement A + BC ® AC + B Also referred to as single displacement One element replaces another Reactants must be an element and a compound. Products will be a different element and a different compound. A + BC ® AC + B 2Na + SrCl2 ® Sr + 2NaCl F2 + LiCl ® LiF + Cl2

Double Replacement AB + CD ® AD + CB ZnS + 2HCl ® ZnCl + H2S Two things replace each other. Reactants must be two ionic compounds or acids. Usually in aqueous solution AB + CD ® AD + CB ZnS + 2HCl ® ZnCl + H2S AgNO3 + NaCl ® AgCl + NaNO3

Combustion A reaction in which a compound (often carbon) reacts with oxygen CH4 + O2 ® CO2 + H2O C3H8 + O2 ® CO2 + H2O C6H12O6 + O2 ® CO2 + H2O

The charcoal used in a grill is basically carbon The charcoal used in a grill is basically carbon. The carbon reacts with oxygen to yield carbon dioxide. The chemical equation for this reaction is C + O2  CO2

How to recognize which type Look at the reactants Element(E), Compound(C) E + E C E + C C + C Acid + Base Look at the Products CO2 + H2O Redox Synthesis Decomposition Single replacement Double replacement Acid/Base reaction Combustion

Examples Synthesis H2 + O2 ® H2O ® Decomposition AgNO3 + NaCl ® Double replacement Zn + H2SO4 ® Single replacement HgO ® Decomposition KBr +Cl2 ® Single replacement Mg(OH)2 + H2SO3 ® Double replacement

Some Properties of Acids Produce H+ (as H3O+) ions in water (the hydronium ion is a hydrogen ion attached to a water molecule) Taste sour Corrode metals Electrolytes React with bases to form a salt and water pH is less than 7 Turns blue litmus paper to red “Blue to Red A-CID”

Acid and Base

Some Properties of Bases Produce OH- ions in water Taste bitter, chalky Are electrolytes Feel soapy, slippery React with acids to form salts and water pH greater than 7 Turns red litmus paper to blue “Basic Blue”

Acid Nomenclature An easy way to remember which goes with which… No Oxygen w/Oxygen An easy way to remember which goes with which… “In the cafeteria, you ATE something ICky”

pH Scale

Law of Conservation of Mass The Law of Conservation of Mass states that in any closed system the amount of mass will remain constant over time. This means that matter can neither be created nor destroyed. In a chemical reaction, the mass of the reactants you start with will equal the mass of the products once the reaction is complete. Even when matter is transformed, the mass will remain constant.

Reaction Energy All chemical reactions are accompanied by a change in energy.  Exothermic - reactions that release energy to their surroundings (usually in the form of heat) Endothermic - reactions that need to absorb heat from their surroundings to proceed.

Endothermic vs. Exothermic