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Chemical Reactions. Maddie Campbell Zach Dakin Brian Sutton Emily Thompson. Physical Changes. A change in physical state Chemical substances don’t change Physical changes are reversible

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chemical reactions

Chemical Reactions

Maddie Campbell

Zach Dakin

Brian Sutton

Emily Thompson

physical changes
Physical Changes
  • A change in physical state
  • Chemical substances don’t change
  • Physical changes are reversible
  • Characteristic 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
Chemical Changes: Chemical Reactions
  • Change old substances into different ones
  • Difficult to reverse
  • All chemical reactions involve a change in energy
energy changes the energy change is often in the form of heat 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 ctd
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 ->CO22H2O
  • If a flame is produced then combustion is called burning

Displacement- When a more reactive element replaces a less reactive element in a compound

Single Displacement- When one element is exchanged between the reactants

  • Zn+CuSO4 -> ZnSO4+Cu

Double Displacement- elements are exchanged between the reactants

  • Pb(NO3)2+2KI -> PbI2+2KNO3(also Ionic Precipitation)
other reactions
Other Reactions

Ionic Precipitation- The production of an insoluble solid from the reaction of 2 or more compounds

  • Pb(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 reactions
Redox Reactions:Oxidation-Reduction Reactions
  • Charges of the elements involved change
  • Always occur in pairs
  • One element loses elections and one element gains electrons
  • ZnO + C -> Zn + CO
  • ZnO has charge, C does not; Zn has no charge, CO does
redox reactions ctd
Redox Reactions Ctd.

Remember OIL RIG! Oxidation Reduction

Is the Is the

Loss of electrons Gain of electrons


Electrolysis- A reaction in which ions move towards electrodes due to an electrical current

  • PbBr (l)2 -> Pb(l) + Br2(g) l: liquid g: gas
  • Electrolyte- an ionic compound which will conduct electricity when it is molten or dissolved in water; electrolytes will not conduct electricity when solid
electrolysis ctd
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
Signs of a Chemical Reaction
  • Bubbling, effervescence, or production of a gas
  • Formation of a precipitate or solid
  • Change in color
  • Change in temperature
  • Light given off
practice problems
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 changes

10) What is a chemical change (reaction)?


1)  double displacement

2)  combustion

3)  single displacement

4)  double displacement

5)  acid-base

6)  synthesis

7)  decomposition

8) 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 burger

10) A chemical change/reaction changes old substances into new and is very difficult to reverse. It involves a change in energy.