PowerPoint Presentation

Cells & BatteriesPacemakerOur bodies use a small electrical signal to control our hearts.

Some people have a problem with it.

Electricity used to operate a pacemaker comes from an electrochemical cell that supplies a steady current.

Lithium & IodineAn electrochemical cell is a package of chemicals designed to produce small amounts of electricity.

The electricity the cell produces comes from chemical reactions.

Other cells, made with other chemicals, are used in things like toys, cars & computers.

ElectrolytePaste or liquid that conducts electricity because it contains chemicals that form ions.

Ion: an atom or a group of atoms that has become chemically charged.2 Main types of cells:Dry CellsChemicals are in a paste; sealed.Chemicals dont leak outUsed in flashlightsWet CellsUses a liquid electrolyte that is usually an acid (sulfuric acid).Many of the earliest cells were wet cells.Used in vehicles2 Main types of cells:Dry CellsWet CellsCheaper and easier to makeDangerous; liquid electrolyte can spill and is highly corrosive.

Wet Cells

Heavy & RigidSolutions?

Problems?

PlasticNormally an insulator, but substances can be added to make it act like a metal.

Not yet as powerful as metal-based cells.

Light & Flexible- can be as thin as a credit card.Primary Cells

Secondary CellsAlso called rechargeable cells

Chemical reactions can be reversed by using an external electrical source to run electricity back through the cell.

Reverse reaction must occur efficiently-Nickel Oxide & cadmium- Advertised as Ni-Cad batteriesNot PerfectEven rechargeable cells wear out in time.BatteriesConnect cells together.

Alessandro Volta made the first usable battery around 1800

Humphry Davy connected 2000 cells together to form one battery in 1807.

Work of scientists let to a whole new field:ElectrochemistryElectrochemistryStudy of chemical reactions involving electricity.

ElectrolysisProcess which splits water into hydrogen and oxygen.

ElectroplatingCoating a cheaper metal with a think layer of gold or silver.Less expensive & stronger. Gold plating

AnodizingCoating aluminum parts with a layer of aluminum oxide.Coating is much harder than just aluminum.

Used in products such as screen doors, airplane or car parts, kitchenware, and jewelery.ElectrorefiningRemoves impurities from metal (like gold).

Automobile companies also use electrochemistry to bond special paints onto car parts.