CHEMISTRY NOTES CHEMICAL REACTIONS & EQUATIONS

SIGNS OF CHEMICAL REACTION Change in temperature –1. ________________: releases energy in the form of heat. You can feel it getting “hotter”

SIGNS OF CHEMICAL REACTION Change in temperature –2. _______________: absorbs heat energy from the reactants. It feels “cooler” than it did at the beginning

SIGNS OF CHEMICAL REACTION Color change _______________ bubbles are seen forming or being released from the reaction

SIGNS OF CHEMICAL REACTION Solid Production - a new, solid substance forms. If a solid is formed in a solution, the solid is called a ___________________

SIGNS OF CHEMICAL REACTION A CHEMICAL REACTION HAS OCCURRED IF THE __________________________ OF THE REACTION ARE DIFFERENT FROM THE __________________________ OF THE REACTION

RULES OF CHEMICAL RXNS Starting chemicals, elements or substances are called ___________________, because they are going to react to form something new.

RULES OF CHEMICAL RXNS Ending chemicals, elements or substances are called ___________________, because they were produced in the reaction.

RULES OF CHEMICAL RXNS All the __________ found at the start of a reaction must be present at the end of a reaction.

RULES OF CHEMICAL RXNS This is the Law of _________________________ All matter (measured as mass) in the _________ must be present in the ____________.

CHEMICAL BONDS A chemical bond occurs between _______________. Bonds only involve _________________________

CHEMICAL BONDS Electrons can be transferred between atoms –Called an _________ Bond –Example:

CHEMICAL BONDS Electrons can be shared between atoms – Called a __________ Bond –Example:

CHEMICAL FORMULAS A shorter, easier way of showing chemical reactions using symbols instead of words ________________ – shows the ratio of elements in a compound

CHEMICAL FORMULAS Subscript numbers behind a symbol tell how many atoms of that element there are in the substance.

CHEMICAL FORMULAS Example: Hydrogen Peroxide’s name means 1 Hydrogen for every 1 Oxygen. The formula is H 2 O 2

CHEMICAL FORMULAS What does “Carbon Dioxide” mean? What is its formula?

CHEMICAL FORMULAS What are other examples of formulas you can think of?

BALANCING EQUATIONS 1. Write the reaction in words. 2. Write the chemical equation.

BALANCING EQUATIONS 3. Count all of the atoms for each element on each side of the equation.

BALANCING EQUATIONS 4. Choose ___________ to place in front of each molecule to make each side of the equation balance.

Classifying Chemical Reactions Synthesis Decomposition Single Replacement Double Replacement

Synthesis Two or more elements combine to form a more complex compound A + B  AB Hand + kerchief  handkerchief Example: C + Cl 2  CCl 4

Decomposition Breaks down compounds into simpler substances AB  A + B Schoolbook  school + book Example: Al 2 O 3  Al + O 2

Replacement A reaction in which one element replaces another in a compound, or two elements in different compounds trade places AB + C  AC + B (Single) AB + CD  AC + BD (Double)