CHEMISTRY NOTES CHEMICAL REACTIONS & EQUATIONS. SIGNS OF CHEMICAL REACTION Change in temperature...

CHEMISTRY NOTESCHEMICAL 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 H2O2

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 + Cl2 CCl4

Decomposition

• Breaks down compounds into simpler substances

• AB A + B

• Schoolbook school + book

• Example: Al2O3 Al + O2

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)