Chemical ReactionsMaddie Campbell

Zach DakinBrian Sutton

Emily Thompson

Physical ChangesA change in physical stateChemical substances don’t changePhysical changes are reversibleCharacteristic properties can be the keys to

designing techniques to separate, mix, or reverse physical changes

Examples: Adding carrots to a salad, putting ketchup on a burger, melting ice

Chemical Changes: Chemical Reactions

Change old substances into different onesDifficult to reverseAll chemical reactions involve a change in

energy

Energy Changes*The energy change is often in the form of heat energy

Endothermic- Net energy change is the addition of energy

A melting object gains energy. It is an endothermic energy change.

* Although melting ice is a physical change- it involves a phase change of matter, it also is an energy change. It is not usually a chemical reaction.

Exothermic- Net energy change is the loss of energy

A burning object gives off energy; it loses energy. It is an exothermic energy change.

*This is a chemical reaction- see combustion and burning on “Types of Reactions Ctd.”

Types of Reactions

Types of Reactions Ctd. Synthesis- 2 or more substances combine to form one substance

6CO2 + 6H2O = C6H12O6 + 6O2 (Photosynthesis)

Decomposition- one substance reacts to form two or more products

Al I3 -> Al + 3I

Combustion- the reaction of a substance with oxygen and the release of energy (exothermic)

CH4 + 202 ->CO22H2OIf a flame is produced then combustion is called burning

DisplacementDisplacement- When a more reactive element

replaces a less reactive element in a compoundSingle Displacement- When one element is

exchanged between the reactantsZn+CuSO4 -> ZnSO4+Cu

Double Displacement- elements are exchanged between the reactants

Pb(NO3)2+2KI -> PbI2+2KNO3 (also Ionic Precipitation)

Other ReactionsIonic Precipitation- The production of an insoluble

solid from the reaction of 2 or more compoundsPb(NO3)2+2KI -> PbI2+2KNO3 (also Double

Displacement)Acid-Base Neutralization- in general, the reaction

of an acid and a base to produce a salt and water

HCl + NaOH -> H2O + NaCl (also Double Displacement)

Redox Reactions:Oxidation-Reduction

ReactionsCharges of the elements involved changeAlways occur in pairsOne element loses elections and one element

gains electronsZnO + C -> Zn + CO ZnO has charge, C does not; Zn has no charge,

CO does

Redox Reactions Ctd.Oxidation Reduction

Oxidation State Increase in oxidation state of an atom or

ion Na->Na+

Decrease in oxidation state of an atom or

ion O->O-2

Electrons Loss of electrons Gain of electronsOxygen Gains oxygen Loses oxygenAgent Oxidizing Agent-

adds oxygen to another substance

Reducing Agent- removes oxygen from

other substancesCellular Process Cellular respiration Photosynthesis

Remember OIL RIG! Oxidation ReductionIs the Is theLoss of electrons Gain of electrons

Electrolysis Electrolysis- A reaction in which ions move towards

electrodes due to an electrical currentPbBr (l)2 -> Pb(l) + Br2(g) l: liquid g: gasElectrolyte- an ionic compound which will

conduct electricity when it is molten or dissolved in water; electrolytes will not conduct electricity when solid

Electrolysis Ctd. Cathode- The electrode in

any type of cell at which reduction takes place; in electrolysis it is the negative electrode

Anode- The electrode in any type of cell at which oxidation takes place; in electrolysis it is the positive electrode

Cation- A positive ion which would be attracted to the cathode in electrolysis

Anion- A negative ion which would be attracted to the anode in electrolysis

Catalyst- A substance which increases the rate of a chemical reaction but itself remains unchanged at the end of the reaction

Signs of a Chemical Reaction

Bubbling, effervescence, or production of a gasFormation of a precipitate or solidChange in colorChange in temperatureLight given off

Practice Problems List what type the following reactions are: 1)  NaOH + KNO3 -> NaNO3 + KOH 2)  CH4 + 2 O2 -> CO2 + 2 H2O 3)  2 Fe + 6 NaBr -> 2 FeBr3 + 6 Na 4)  CaSO4 + Mg(OH)2 -> Ca(OH)2 + MgSO4 5)  NH4OH + HBr -> H2O + NH4Br 6)  Pb + O2 -> PbO2 7)  Na2CO3 -> Na2O + CO2 8) What is a physical change?9) Give two examples of physical changes10) What is a chemical change (reaction)?

Answers1)  double displacement 2)  combustion 3)  single displacement 4)  double displacement 5)  acid-base 6)  synthesis 7)  decomposition8) A physical change is a change in physical state; it does not change the

chemical substance and is easier to reverse than a chemical reaction.9) Including, but not limited to: melting ice, adding carrots to a salad, and

putting ketchup on a burger10) A chemical change/reaction changes old substances into new and is very

difficult to reverse. It involves a change in energy.