Chapter 14 Chemical Reactions

Forming New Substances O ___________ -a process in which one or more substances change to make _____________________ ______________ O The ________ and ________ _________of the new substance _______ from those of the original substances. O Examples of chemical changes: O O

Signs of a Chemical Reaction O O O O formation of a solid ___________ O _____________- Solid substance that is formed in a solution

Signs of a Chemical Reaction O A change of properties: O The signs can help you identify a chemical reaction, but they do not guarantee a reaction took place. O Ex. Boiling water gives off gas, but this is a physical change. O The most important sign that a chemical change took place is the _______________ ____________________________________.

Chemical Bond O _____________ -force that holds two atoms together in a molecule. The original bonds must _______ and new bonds must be ______. O Ex 1: H 2 and Cl 2 O Chlorine gas has a greenish-yellow color O Hydrogen gas is flammable O Hydrogen chloride is a nonflammable, colorless gas. O Ex 2: Na and Cl 2 O Na is a metal that reacts violently with water O Cl is a greenish-yellow poisonous gas O Sodium chloride is a harmless substance that almost everyone uses.

Ch 14.2 Chemical Formulas and Equations O ______________ - a shorthand way to use ________________ and ___________ to represent a substance. It shows how many atoms of each kind are present in a molecule.

Chemical Formulas and Equations O Subscript- number written below and to the right of a chemical symbol in a formula. O *If no subscript is present, it means only 1 atom of that element is present. O Ex: H 2 O H = O = C 6 H 12 O 6 C =H=O= CO 2 C = O =

Writing formulas for Covalent Compounds O composed of 2 nonmetals O use prefixes O if there is only one atom of the first element drop the mono- prefix O change 2 nd elements suffix to –ide O Ex: CO 2 N 2 O Mono- 1 Hexa- 6 Di- 2 Hepta- 7 Tri- 3 Octa- 8 Tetra- 4 Nona- 9 Penta- 5 Deca- 10

Writing formulas for Ionic Compounds O composed of a metal and a nonmetal O put the metal first, nonmetal second overall charge must be 0. O charges of the ions will cancel out O criss-cross rule O change suffix of nonmetal to –ide O Ex: NaCl MgCl 2

Chemical Equations O _______________ - chemical symbols and formulas as a shortcut to describe a chemical reaction O ____________ - the starting materials in a chemical reaction O ____________ -the substance formed from a reaction O Ex: C + O 2  CO 2 

How do new substances form in a chemical reaction? O 1. O Molecules are always moving O If molecules bump into each other with enough energy, the chemical bonds in the molecules break. O 2. O 3.

The Reason Equations Must be Balanced: O ·Atoms are never ____ or _______ in a chemical reaction O ·They are just _____________ O ·The # of atoms in the __________ must __ # of atoms in the ___________ O This is called balancing the reaction

Law of Conservation of Mass O ___________________ -Mass is neither created or destroyed in ordinary chemical and physical changes

How to Balance an Equation: O You must use ___________- number placed in front of a chemical symbol or formula O Ex 1: 2CO means ____________________________ O Ex 2: 2H 2 O means ___________________________ O Total there are __ hydrogen atoms and __oxygen atoms O ·Only coefficients are changed when balancing equations – ________________!! O ___H 2 + ___O 2  ___H 2 O | | |

Balancing Chemical Reactions ____ Na + ____Cl 2 → ____NaCl Na Na O O ____ N 2 + ­­_ ____ H 2 → ____ NH 3 N N H H

14.3 Types of Reactions O _____________- A reaction in which two or more substances combine to form one new compound. O A + B = AB O Ex: Sodium + Chlorine = Sodium Chloride

Synthesis Reaction

Types of Reactions O ______________ -A reaction in which a single compound breaks down to form two or more simpler substances. O AB = A + B O Ex: Carbonic Acid = Water and carbon Dioxide

Decomposition Reaction

Types of Reactions O _______________________ - A single element replaces another element that is part of a compound. O Products are a new compound and a different single element O O Ex: O *The more reactive element can displace a less reactive element. O Ex: Copper can replace Silver, but the opposite can’t occur.

Single Replacement

Types of Reactions O _____________________- A reaction in which ions from two compounds switch places. O AB + CD = AD + CB O EX: Sodium Chloride + Silver Fluoride = Sodium Fluoride + Silver Chloride

Double Replacement

14.4 Energy and Rates of Chemical Reactions O ________________________- Reaction in which energy is released. O EXO means “__________” O Ex: 2Na + Cl 2  2NaCl + ________ O ________________________ - Reaction in which energy is taken in O ENDO means “__________” O Ex: 2H 2 O + _________  2H 2 + O 2

Law of Conservation of Energy O _______________________________ - Energy cannot be created or destroyed O Energy can be _____________ from one object to another O _________________ - the speed at which new particles form O __________________ - The smallest amount of energy that molecules need to react.

Factors that Affect Reaction Rate O _________________ – the higher the temperature, the faster the reaction rate O _________________- The higher the concentration of reactants, the faster the reaction rate O ________________ - (amount of exposed surface on a substance) The larger the surface area, the faster the reaction rate O ______________- A substance that slows down a reaction. Ex: Preservatives in food slow down bacteria growth. O ______________- A substance that speeds up a reaction without being permanently changed. NOT A REACTANT!! Ex: Enzymes speed up reactions in your body.